DE10134181A1 - P-type nitride semiconductor manufacturing method for light emitting and receiving elements, involves cooling substrate of nitride semiconductor layer in environment of hydrogen - Google Patents

Abstract

A p-type nitride semiconductor layer is formed on a substrate maintained at temperature of more than 950 deg C by introducing p-type dopant, nitrogen and group III elements. The substrate is then cooled to the temperature of 700 deg C in the environment of hydrogen.

Description

FIELD OF THE INVENTION

The present invention relates to a p-type nitride Semiconductors among those based on gallium nitride (Group III-V) for use in light emitting inputs directions that have blue light or another light with cure radiate zero wavelength; especially a nitride Semiconductor that has no temper or glow after growing action (hereinafter referred to as "temper" treatment) calls. One method of manufacturing a semiconductor is also included in the present invention.

GENERAL PRIOR ART

A semiconductor based on gallium nitride (group III-V), that has a relatively large bandgap is one of the future materials for the light with short Wavelength emitting devices are suitable, the used in optical information processing units that keep the growing amount of information handle. With such light emitting device, such as a diode device or a laser device is a PN transition is the essential structure where the beams in the Near the junction can be recombined and the light out shines. As is well known, it is not easy to find one Nitride semiconductors with low resistivity because of the p-type nitride semiconductor that Magnesium, Mg, or another acceptor that is doped Activation rate or speed of the acceptor against above the donor is significantly lower.  

The p-type nitride semiconductor shows a high value of specific resistance when after growing on space temperature is returned. To a low specific To get resistance, it was normal practice to conductive nitride semiconductor an after-anneal or another Heat treatment to apply the hydrogen one from Mag nesium and hydrogen complex formed from the magnesium to separate. Research activities are carried out to a p-type nitride semiconductor with low spec resistance without the use of post-annealing put. If this turns out to be successful, it works this is also an advantage for improved productivity at such facilities.

For example, in U.S. Patent Publication 5,932,896 (of Japanese Patent Laid-Open No. 135575/1998) is a ver drive to manufacture a p-type nitride semiconductor disclosed without the use of post-annealing.

The method disclosed in the above publication uses a metal organic vapor deposition (MOCVD) process to grow a p-type nitride semiconductor on a sapphire substrate containing an organic magnesium compound containing such a Group III source as trimethyl gallium (TMG ) contains such a nitrogen source as ammonia (NH ₃ ) and a p-type dopant on the substrate at 1100 ° C using a nitrogen carrier gas, the hydrogen gas in a concentration of 0.8-20 vol .-% (capacity percent) contains. In this way, the formation of a magnesium-hydrogen complex is blocked and a p-type nitride semiconductor is provided which shows a low resistivity during the growth phase. It also discloses a cooling process in which the temperature in an atmosphere of nitrogen gas containing about 32 vol% ammonia is reduced to 350 ° C and then the ammonia supply is stopped and the temperature is reduced to room temperature.

The conventional manufacturing method described above a p-type nitride semiconductor, which be the post-annealing but has the following problems. How namely the inventor of US Pat. No. 5,932,896 described above and an whose author in a work (Applied Physics Letters, Vol. 72, (1998), p. 1748), the activity deteriorates rate or rate of magnesium clearly if hydrogen during the crystal growth process concentration only increased from 2.4% to 3.7%, which means that a p-type nitride semiconductor can only be obtained can if he is under a very low hydrogen concentration tion is bred. What's more: if a nitride semiconductor is grown under a low hydrogen concentration, turns out that the surface migration is insufficient and certain specific atoms are not attached to each optimal points of the surface are arranged what it difficult to get a good crystal.

SUMMARY OF THE INVENTION

The present invention addresses those described above Problems and strives to use a p-type nitride Offer higher quality semiconductors without treatment need night tempering.

The process for producing a p-type nitride Semiconductor includes a process of forming a p- conductive nitride semiconductor with low specific Wi the state of growth and a cooling process in which the cooling time or the atmosphere is controlled so that the property of low resistivity in a practical area that is held as p-type Semiconductor is usable.

Described specifically in a manufacturing process development of a p-type nitride semiconductor of the present Invention, the source of the p-type dopant, the nitrogen  source and Group III source on a substrate performed, which is held at a temperature of 600 ° C or higher ten to a p-type nitride semiconductor layer low resistivity on the substrate and becomes the p-type nitride semiconductor layer cooled substrate. During the cooling process takes the hole carrier density in the p-type nitride Semiconductor layer.

This results in a p-type nitride semiconductor layer on the egg nem substrate formed in an atmosphere that a speci fish amount of hydrogen that contains a deactivation suppresses the p-dopant, and takes the hole carrier density of the p-type nitride semiconductor layer on a Ni veau from which the property of low specific Resistance can be maintained. That way a p-type nitride semiconductor with a higher crystal quality made available without any treatment of post-heating is required.

In the present process for producing a p-type Nitride semiconductor, it is preferred that during the cooling process the hole carrier density of the p-type nitride semiconductor decreases about 0% -95%.

For example, assuming that the hole carrier density is about 2.0 × 10 ¹⁷ cm ^-3 immediately after growing, a concentration of about 1.0 × 10 ¹⁶ cm ^{-3 can be} maintained even if the hole carrier density is around 95 % decreased. Thus, a p-type nitride semiconductor is provided that works practically well.

In the present process for producing a p-type Nitride semiconductor, it is preferred that it cool down started a procedure to lower the substrate temperature from the growing temperature to about 600 ° C within 30 min ent holds.  

This ensures that the hole carrier density of a p- conductive nitride semiconductor layer to maintain the Low resistivity property for one practical work is sufficient.

In the present process for producing a p-type Nitride semiconductor, it is preferred that the atmosphere for the formation of a semiconductor layer about 5-70 vol .-% What contains substance.

If an organometallic material as the source of the element Group III or p-type dopant is used usually hydrogen to increase decomposition efficiency and promote surface migration in the atmosphere hold. However, if the hydrogen concentration exceeds 70% is the deactivation caused by the hydrogen effect on the acceptor significant. Deactivating the p- Doping material can be safely suppressed if the What hydrogen concentration to 5% -70% according to the present Er is controlled.

In the present process for producing a p-type Nitride semiconductor, it is preferred that the atmosphere is introduced during the cooling process until the substrate temperature reached about 600 ° C from the growing temperature, contains about 0-50 vol .-% hydrogen.

This can deactivate a p-type nitride Semiconductors are suppressed due to the hydrogen and becomes the property of low resistivity a relatively high hole carrier density in a p-type Nitride semiconductor layer well maintained.

In the present process for producing a p-type nitride semiconductor, it is preferred that the atmosphere which is introduced during the cooling process until the substrate temperature reaches about 600 ° C. from the growth temperature contains ammonia, NH ₃ .

This can remove nitrogen from the surface of the grown p-type nitride semiconductor and, as a result, prevents deterioration of the surface become.

To accomplish the task described earlier, this forms present manufacturing process in the process of training a p-type nitride semiconductor layer a p-type Nitride semiconductor with low resistivity and then make a specific plan for that Cooling process ready, the specific substrate temperature tur range, namely a substrate temperature range of about 950 ° C-700 ° C, in which the deactivation of the p- Doping material in the p-type nitride semiconductor layer occurs.

The present method for manufacturing is specifically described position of a p-type nitride semiconductor, the p-type Nitride semiconductor layer during the spe specific substrate temperature range under a certain specific condition cooled when the deactivation of the p-doping material hardly occurs, which specific Be condition from a combination of the hydrogen concentration tion in the atmosphere and the cooling time.

In the present process for producing a p-type Nitride semiconductor becomes the p-type nitride layer during of the specific substrate temperature described above empire under a certain specific condition cools, with the deactivation of the p-dopant hardly occurs, which specific condition results from a station wagon nation of hydrogen concentration in the atmosphere and Cooling rate composed.  

This makes it possible for a p-type nitride semiconductor the property of low resistivity in maintains a certain area in which it is considered practical p-type semiconductor can work.

Furthermore, a p-type nitride semiconductor relates to the present invention a p-type nitride semiconductor based on a substrate at a growing temperature of 600 ° C or higher is formed, in which the hole carrier density immediately after the cooling process about 5% -100% of that in the cultivated temperature is.

In a case where the hole carrier density is about 2.0 × 10 ¹⁷ cm ^-3 immediately after growing, a concentration of about 1.0 × 10 ¹⁶ cm ^{-3 can be} provided even if the hole carrier density is 5% of that directly decreased after breeding. Thus, it provides a p-type nitride semiconductor that works in practical use.

Another p-type nitride semiconductor of the present Invention relates to a p-type nitride semiconductor which on a substrate in succession at the growing temperature of 600 ° C or higher is formed, the p-type nit rid semiconductors exposed to it on the top surface the hydrogen concentration is close to the Top is the same or within about 10 times that inside the p-type nitride semiconductor lies.

In the conventional p-type nitride semiconductor, the through the processes produced by a treatment accompanied by night heating is the hydrogen con center near the exposed top by more than 10 times larger than that inside the p-type Nitride semiconductor. With a p-type nitride semiconductor however, the hydrogen con remains in the present invention center near the top of the p-type nitride  Semiconductor at the same level, or within about 10 times that inside the p-type nitride Semiconductor. Therefore, according to the present invention a p-type nitride semiconductor with the p-type dopant an improved activation rate or speed Semi asked.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view showing the structure of a p-type nitride semiconductor in Embodiment 1 of the present invention.

Fig. 2 is a graph showing the dependence of the hole carrier density on the cooling time during the cooling process in a method for producing a p-type nitride semiconductor in Embodiment 1 of the present invention.

Fig. 3 is a cross-sectional view showing the structure of a p-type nitride semiconductor in the embodiment 2 of the present invention.

Fig. 4 is a graph showing the distribution of the hydrogen concentration in the depth direction at the light emitting means with the nitride semiconductor in the embodiment 2, including a first modification and a comparative sample of the present invention.

Fig. 5 is a graph showing the dependence of the ren hole carrier density of the holding temperature for the substrate during the cooling process in a procedural conductive p-for manufacturing a nitride semiconductor shows in an embodiment of the present invention.

Fig. 6 is a graph showing the dependence of the hole carrier density on the time for cooling the substrate from about 950 ° C to about 700 ° C during the cooling process in a method for producing a p-type nitride semiconductor in one embodiment of the present invention.

Fig. 7 is a graph showing the relationship between the hydrogen concentration in the atmosphere and the time for cooling the substrate from about 950 ° C to about 700 ° C during the cooling process in a process for producing a p-type nitride semiconductor shows in an embodiment of the prior invention.

Fig. 8 is a graph showing the relationship between the hydrogen concentration in the atmosphere and the cooling rate of the substrate at about 800 ° C during the cooling process in a process for producing a p-type nitride semiconductor in an embodiment of the present invention ,

Fig. 9 is a cross-sectional view of the lead form the structure of a p-type nitride semiconductor in a further of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are presented below Described with reference to the drawings.

(Embodiment 1)

There will be a first exemplary embodiment of the present ing invention with reference to the accompanying drawings described.  

Fig. 1 is a cross-sectional view showing the structure of a p-type nitride semiconductor according to a first beispielhaf th embodiment of the present invention. On a substrate 11 made of sapphire, there is a buffer layer formed of gallium nitride (GaN) to reduce the lattice offset between a specific semiconductor that is to be grown on the substrate 11 and the sapphire and a p-type nitride formed of GaN. Semiconductor layer 13 arranged one above the other in this order.

The method for producing the above p-type nitride semiconductor layer is described below. First, the substrate 11 having a mirror-finished main surface is placed in a reaction chamber (not shown) and held by a substrate holder, and then the temperature of the substrate is raised to about 1000 ° C and hydrogen gas is supplied to the substrate 11 while it is is heated for about 10 minutes. This removes stains from organic matter and moisture adhering to the main surface.

The substrate temperature is reduced to about 550 ° C and then nitrogen gas as a carrier gas with a throughput of about 16 liters / min and ammonia gas, NH ₃ , as a nitrogen source with a throughput of about 4 l / min, trimethyl gallium (TMG) as the source of the group III with a throughput of about 40 µmol / min on the substrate 11 . Thus, the buffer layer 12 made of GaN is grown on the main surface of the substrate 11 to a thickness of 25 nm.

The TMG feed to the reaction chamber is stopped once and the substrate temperature is raised to about 1050 ° C; and on the buffer layer 12 , a 2 µm thick p-type nitride semiconductor layer 13 made of Mg-doped GaN is grown by using nitrogen gas with a throughput of about 13 l / min, hydrogen gas with a throughput of about 3 l / min as the carrier gas and ammonia gas, NH ₃ , with a throughput of about 4 l / min, TMG with a throughput of about 80 µmol / min and magnesium as p-dopant containing bicyclopentadienyl magnesium (Cp ₂ Mg) with a throughput of about 0.2 µmol / min on the substrate 11 for about 60 min. The above throughput of hydrogen gas includes the hydrogen gas needed to vaporize the TMG and the Cp ₂ Mg.

The supplies of TMG and Cp ₂ Mg to the reaction chamber are set and then the substrate 11 is cooled down from the growing temperature to room temperature while nitrogen gas with a throughput of about 13 l / min, hydrogen gas with a throughput of about 3 l / min and ammonia gas, NH ₃ , with a throughput of about 4 l / min as ambient gas on the substrate 11 . After the cooling has ended, the substrate 11 carrying the p-type nitride semiconductor layer 13 is removed from the reaction chamber.

Specific features contained in the cooling process of the present invention will now be described below, which cooling process is to be applied to the substrate carrying the p-type nitride semiconductor layer 13 .

Fig. 2 is a graph showing the dependency of hole carrier density of the cooling time during the cool down process in a method for producing a p-type nitride semiconductor in the first exemplary embodiment of the present invention. The hole carrier density was measured with the p-type nitride semiconductor layers 13 , which had five different cooling periods from 5 minutes to 40 minutes to reduce the substrate temperature from 1050 ° C., or the growth temperature, to 600 ° C. The measurement of the hole carrier density was carried out by measuring the Hall effect with a square sample chip with 5 mm, which was produced by separating substrates 11 provided specifically for the measurement in five different cases.

As can be seen in Fig. 2, all five test chips show the p-line and the hole carrier density decreases with those that had a longer time to cool from the growing temperature to 600 ° C. By extrapolating the straight line from FIG. 2 to the y-part for the cooling time zero, it can be ascertained that the p-type nitride semiconductor layer 13 of the present embodiment directly follows a p-type line with approximately 2 × 10 ¹⁷ cm ^-3 hole carrier density of their breeding shows.

Fig. 2 also shows that the hole carrier density at 5 min cooling time is 1.2 × 10 ¹⁷ cm ^-3 , at 20 min cooling time is 3.0 × 10 ¹⁶ cm ^-3 , which is about 7% of the concentration before cooling corresponds, and at 30 min cooling time is 1.0 × 10 ¹⁶ cm ^-3 , which speaks ent about 5% of the concentration before cooling. The case with the cooling time of 30 minutes is almost at the lower limit that can be used for a p-type layer in a device. In the case with a cooling time of 40 minutes, the concentration is 2.2 × 10 ¹⁵ cm ^-3 , which indicates that the carrier density is not sufficient for use in a device.

(First modification of embodiment 1)

Below is a method of making a p-type Nitride semiconductor layer according to a first modification Game of embodiment 1 described.

The first buffer layer 12 and the p-type nitride semiconductor layer 13 with a hole carrier density of approximately 2 × 10 ¹⁷ cm ^-3 are formed by the same method as in embodiment 1 in the order on the substrate 11 as in FIG. 1 shown.

The dependence of the hole carrier density on the concentration of hydrogen gas contained in the ambient gas during the cooling process in the first modification example is described below. The hole carrier density was measured with those that passed through four different atmospheres with four different hydrogen gas concentrations, 0%, 30%, 50% and 70%. The concentration of ammonia gas, NH ₃ , in each of the atmospheres was about 20%, the rest was nitrogen gas. The substrate was cooled from about 1050 ° C, or the growth temperature, to about 600 ° C in about 5 minutes.

The results of the measurement are:

• 1. 0% hydrogen concentration about 2 × 10 ¹⁷ cm ^-3 , equal to that immediately after growing
• 2. 30% hydrogen concentration about 4.2 × 10 ¹⁶ cm ^-3
• 3. 50% hydrogen concentration about 1 × 10 ¹⁶ cm ^-3 , equal to about 5% of that immediately after growing
• 4. 70% hydrogen concentration about 2.5 × 10 ¹⁵ cm ^-3 , equal to about 1% of that immediately after growing

As can be seen above, the p-type layer is used for a ver Use of an institution is inadequate if it is in a Cooled environment with a hydrogen concentration of 70% even if it reaches 600 ° C in a period of 5 minutes is cooled.

(Second modification of embodiment 1)

Below is a method of making a p-type Nitride semiconductor layer according to a second modification example of embodiment 1 described.

The first buffer layer 12 and the p-type nitride semiconductor layer 13 with a hole carrier density of approximately 2 × 10 ¹⁷ cm ^-3 are formed by the same method as in embodiment 1 in the order on the substrate 11 as in FIG. 1 shown.

The dependency of the hole carrier density on the concentration of ammonia gas, NH ₃ , contained in the atmosphere during the cooling process is described in the second modification example. The concentration of hydrogen gas in the atmosphere was about 15%, the rest was nitrogen gas. The substrate was cooled from about 1050 ° C, or the growing temperature, to about 600 ° C in about 5 minutes.

As a result of the measurement, it was confirmed that there was little difference in the rate of decrease of the hole carrier density during the cooling process even when the ammonia gas concentration, NH ₃ , was varied; it remains at a level which corresponds to a concentration of ammonia gas, NH ₃ , of 20%. When the concentration of ammonia gas, NH ₃ , is in a range of 0% -0.5%, the crystal property deteriorates due to separation of nitrogen from the surface of the p-type nitride semiconductor layer 13 .

(Third modification of embodiment 1)

A method for producing a p-type nitride semiconductor layer according to a third modification example of embodiment 1 is described below. In the present modification example, the dependency of the hole carrier density during the formation of the p-type nitride semiconductor layer 13 shown in FIG. 1 on the hydrogen gas concentration in the carrier gas is described. In embodiment 1, the hydrogen gas concentration in the carrier gas was about 15%; while in the present modification example the concentration of the hydrogen gas in the carrier gas varies in five steps with an interval of 5% from 0% to 20% and in six steps with an interval of 10% from 20% to 80%, a total of eleven steps. In the case of a hydrogen gas concentration of 0%, TMG or Cp ₂ Mg were evaporated using nitrogen gas.

The result of the measurements on each of the p-type nitride semiconductor layers 13 grown in an atmosphere in which the hydrogen gas concentration falls in a range of 5% -70% indicated that the hole carrier density was 1 × immediately after the growth 10 was ¹⁶ cm ^-3 or more, which means that they have a p-type property; the value was obtained similar to what was shown in Fig. 2 by extrapolating the cooling time from zero. More specifically, the hole carrier density is about 5 × 10 ¹⁶ cm ^-3 or more with a hydrogen gas concentration of about 5% -50%, about 1 × 10 ¹⁷ cm ^-3 or more with a hydrogen gas concentration of about 10% -20%. If, in other cases, a hydrogen concentration of 15% is used for cultivation, the perforated carrier density shows its maximum value at a height of 2 × 10 ¹⁷ cm ^-3 immediately after cultivation.

With regard to the total line width at half the height hey the rocking curve which is a criterion for evaluating the Represents crystal property, it becomes with increasing what hydrogen gas concentration lower; the entire line width at half the maximum value is less than 300 s if the concentration of the hydrogen gas is 10% or more. However, when in an atmosphere with a hydrogen gas concentration is grown from zero, the entire lines width at half the maximum of the rocking curve at the X-ray diffraction 500 s to a significantly worsened one Crystal property. Furthermore, the high specific Wi was impossible to measure the hole carrier density.

When in an atmosphere with a hydrogen gas concentration one is bred by about 80%, it does the same Because of the high specific resistance impossible, the hole to measure carrier density. The reason for this is probably one increased amount of GaN during growth recorded hydrogen atoms, which the Aktivierungsge Magnesium speed reduced.

Although ammonia, NH _{3 was used} as the nitrogen source in the present embodiment, other organic nitrogen materials such as hydrazine, N ₂ H ₄ , ethyl adzide, C ₂ H ₅ NH ₂ can also be used for the purpose.

(Embodiment 2)

There will be a second exemplary embodiment of the present ing invention with reference to the accompanying drawings described.

Fig. 3 is a cross-sectional view showing the structure of a light emitting device having nitride semiconductor according to a second exemplary embodiment of the present invention. The epitaxial layer of a light emitting device with nitride semiconductor in the second embodiment comprises a buffer layer 22 made of undoped GaN, which is arranged on a sapphire substrate 21 , an n-type contact layer 23 made of Si doped GaN, a light emitting layer 24 made of undoped In GaN, a first plating layer 25 made of undoped GaN, a p-type second plating layer 26 made of Mg-doped AlGaN and a p-type contact layer 27 made of Mg-doped GaN, which are arranged one above the other in this order , On the p-type contact layer 27 there is a translucent positive electrode 28 , which consists of Ni and Au layers, which are arranged one above the other in the order. A negative electrode 29 made of Al is formed on the exposed area of the n-type contact layer 23 . Thus, the present light from the radiating device is a light-emitting diode with a pn junction between the n-type contact layer 23 and the second cladding layer 26 , the undoped, light-emitting layer 24 and the first cladding layer 25 being arranged between them.

In the following, a method for producing the light diodes ode described with the above structure.  

First, a substrate 21 having a mirror-finished main surface is placed in a reaction chamber (not shown) and held by a substrate holder, and then the temperature of the substrate is raised to about 1000 ° C and hydrogen gas is supplied to the substrate 21 while it is is heated for about 10 minutes. This removes stains from organic matter and moisture adhering to the main surface and provides a clean surface.

The substrate temperature is reduced to about 550 ° C and then nitrogen gas as a carrier gas with a throughput of about 16 l / min and ammonia gas, NH ₃ , as a nitrogen source with a throughput of about 4 l / min and trimethyl gallium (TMG) as a source of the group III with a throughput of about 40 µmol / min on the substrate 21 ; thus, the buffer layer 22 with GaN is formed on the main surface of the substrate 21 with a thickness of 25 nm. The throughput of the hydrogen gas in the carrier gas includes the hydrogen gas required to vaporize the TMG or the Cp ₂ Mg.

The TMG supply to the reaction chamber is adjusted once and the substrate temperature is raised to approximately 1050 ° C., and a 2 μm thick p-type contact layer 23 made of Si-doped GaN is grown on the buffer layer 22 by using nitrogen gas with a throughput of approximately 13 l / min, hydrogen gas with a throughput of about 3 l / min as carrier gas and ammonia gas, NH ₃ , with a throughput of about 4 l / min, TMG with a throughput of about 80 µmol / min and magnesium and 10 ppm silicon containing monosilane, SiH ₄ , an n-doping material, with a throughput of about 10 cm ³ / min for about 60 min on the substrate 21 .

The TMG and SiH ₄ gas supplies are stopped and then the substrate temperature is lowered to about 750 ° C. At this growth temperature, an SQW light-emitting layer 24 made of 3 nm thick InGaN is grown on the n-type contact layer 23 by using nitrogen gas as carrier gas with a throughput of about 14 l / min. NH ₃ , with a throughput of about 6 l / min, TMG with a throughput of about 4 µmol / min and trimethylindium (TMI), another source of group III, with a throughput of about 5 µmol / min onto the substrate 21 to be led. The In composition in the light emitting layer 24 of the present case is about 0.2.

The supply of the TMI is stopped while the nitrogen carrier gas, the ammonia gas, NH ₃ , as the nitrogen source and the TMG as the group III source are further flowed to the substrate 21 with the flow rate accordingly. In this way, a first plating layer 25 made of GaN is grown on the light-emitting layer 24 to a thickness of 10 nm while the temperature of the substrate is raised to approximately 1050 ° C.

After the substrate temperature reaches 1050 ° C., nitrogen gas with a throughput of about 13 l / min, hydrogen gas with a throughput of about 3 l / min as carrier gas and ammonia gas, NH ₃ , with a throughput of about 4 l / min, TMG with a throughput of about 40 µmol / min, trimethylaluminium (TMA) as a further source of group III with a throughput of about 6 µmol / min and Cp ₂ Mg with a throughput of about 0.1 µmol / min on the substrate 21 to grow a second plating layer 26 of Mg-doped AlGaN on the first plating layer 25 to a thickness of 0.2 µm.

After adjusting the TMA supply and maintaining the substrate temperature at about 1050 ° C, nitrogen gas with a throughput of about 13 l / min, hydrogen gas with a throughput of about 3 l / min as carrier gas and ammonia gas, NH ₃ , with a throughput of about 4 l / min, TMG with a throughput of about 80 µmol / min and Cp ₂ Mg with a throughput of about 0.2 µmol / min on the substrate to form a p-type contact layer made of Mg-doped, to grow p-type GaN on the second plating layer 26 to a thickness of 0.3 µm.

After the p-type contact layer 27 is formed, the temperature is lowered from the growing temperature to room temperature, while nitrogen gas with a throughput of about 13 l / min, hydrogen gas with a throughput of about 3 l / min and ammonia gas, NH ₃ , with a throughput of about 4 l / min as ambient gas into the reaction chamber. The substrate 21 , which has an epitaxial layer formed of a plurality of nitride semiconductor layers, is taken out of the reaction chamber. In the ambient gas, the hydrogen gas concentration is about 15%, the concentration of ammonia gas, NH ₃ , is about 20%. The substrate 21 was cooled from the growing temperature, about 1050 ° C., to 600 ° C. in 5 minutes.

The nitride semiconductor layers thus provided, including the p-type second plating layer 26 and the p-type contact layer 27 , were formed by the same growth process and the cooling method as in embodiment 1 . Therefore, better p-type semiconductor layers with low resistivity have been provided without undergoing the post-annealing treatment needed to activate the Mg with which the second plating layer 26 and the p-type contact layer are doped.

Next, for example by using a CVD process, a silicon oxide layer is formed on the p-type contact layer 27 by deposition, a special pattern is provided by photolithography to form an etching mask, and then the epitaxial layer is replaced by a reactive one Ion etching using the mask is etched until the n-type contact layer 23 is exposed.

An n-electrode 29 is selectively formed on the exposed surface of the n-type contact layer 23 using, for example, an evaporation process; in the same manner, a p-electrode 28 is selectively formed on the p-type contact layer 27 .

The bottom or the opposite side of the epitaxial layer of the substrate 21 is ground to bring the thickness of the substrate 21 to about 100 microns, and the substrate is separated by cutting into chips. Each of the separated chips is attached to a foot with electrodes thereon with the surface supporting the device facing up. The p-electrode 28 and the n-electrode 29 of the chip are connected to respective electrodes of the foot and then the entire chip is molded with a resin to become a finished light-emitting diode.

It has been confirmed that the by Pro zedur provided blue light with a light emitting diode Peak wavelength of 470 nm emits when at 20 mA Electricity is operated in the forward direction. The light output was 2.0 mW, the operating voltage in the forward direction be carried 4.0 V.

(First modification of embodiment 2)

A light-emitting diode having the structure of FIG. 3 was provided by modifying the cooling time of embodiment 2 to 25 minutes, in which the temperature of the substrate 21 carrying the epitaxial layer rose from the growth temperature, approximately 1050 ° C., to 600 ° C. is lowered. The above LED emitted blue light with a peak wavelength of 470 nm when it was operated with a current of 20 mA in the forward direction. The light output was 0.5 mW, the operating voltage in the forward direction was 5.0 V.

(Comparative Example)

A light-emitting diode with the structure of FIG. 3 was provided by modifying the cooling time of embodiment 2 to 40 min, in which the temperature of the substrate 21 carrying the epitaxial layer rose from the growth temperature, approximately 1050 ° C., to 600 ° C. is lowered. The above light emitting diode was operated with a current of 20 mA in the forward direction, but the electrical current did not flow due to the high resistance, so no light was emitted.

Fig. 4 is a graph showing the hydrogen distribution in the depth direction from the surface with the light-emitting device with nitride semiconductor in Embodiment 2, in the first modification of Embodiment 2 and the comparative example by SIMS (secondary Ion mass spectroscopy) was measured. The hydrogen concentration is shown in terms of the three different time periods described above that were provided for cooling. In Fig. 4, the areas corresponding to the semiconductor layers of Fig. 3 are identified accordingly by providing the same markings. Curve 1 A shows the case of Embodiment 2 are, in which the cooling time of the growth temperature of about 1050 ° C to 600 ° C for 5 minutes, curve 1 B illustrates the case of the modification in which it is 25 min, and curve 1 C represents the case of the comparative example in which it is 40 min.

Curve 1 A in Fig. 4, which shows the cooling time for 5 min, indicates that the hydrogen concentration ^-3 is, at a point near the surface of about 3.0 × 10 ¹⁹ cm which concentration down with the progression toward the substrate (the direction towards the n-type contact layer 23 ) decreases, and in the second plating layer 26 the hydrogen concentration becomes almost constant at about 1.0 × 10 ¹⁹ cm ^-3 . In the first plating layer 25 , the light emitting layer 24 and the n-type contact layer 23 , it is less than 2.0 × 10 ¹⁸ cm ^-3 , which is the lower detection limit.

Curve 1 B of the first modification, which is the cooling time 25 min, indicates that the hydrogen concentration ^-3 is cm to ei nem point near the surface of about 1.0 × 10 ²⁰ decreases which concentration with the progress towards the substrate, and in the second plating layer 26 , the concentration of hydrogen is almost constant at about 1 × 10 ¹⁸ cm ^-3 .

Curve 1 C of the comparative example, illustrating the cooling time 40 min, indicates that the hydrogen concentration of egg nem point near the surface of about 3.0 × 10 ²⁰ cm ^-3, decreases which concentration with the progress towards the substrate, and the second plating layer 26 , the hydrogen concentration is almost constant at about 1 × 10 ¹⁹ cm ^-3 .

FIG. 4 also indicates that in the case where the cooling time is shorter than 25 minutes, the hydrogen concentration at the top of the p-type contact layer 27 is within 10 times that in the second plating layer 26 .

As the above embodiment 2 and its first modification indicate, a better p-type layer provided with a low resistivity immediately after growing is made available by doing so during the growth of the p-type second plating layer 26 and the P-type contact layer 27 used carrier gas contains about 5 to 70 vol .-% hydrogen, preferably about 15 vol .-% hydrogen.

Furthermore, the decreasing rate of the hole carrier density of the p-type semiconductor layer can be suppressed to about 0% to 95% by the cooling time in the cooling process in which it is cooled from the growing temperature higher than 600 ° C to about 600 ° C is set to be less than about 30 minutes, preferably about 5 minutes, and by making the atmospheric gas with hydrogen gas at about 50% by volume or less and ammonia gas, NH ₃ , at about 0.5% by volume. % or more is formed. As a result, a light-emitting device with nitride semiconductor with a low operating voltage in the forward direction and high performance is performed.

(Embodiment 3)

Fig. 1 is a cross-sectional view showing the structure of a p-type nitride semiconductor according to a third beispielhaf th embodiment of the present invention. On a substrate 11 made of sapphire, a buffer layer 12 made of GaN and a p-type nitride semiconductor layer 13 made of GaN are arranged one above the other in the order.

In practice, the substrate 11 is placed in a reaction chamber (not shown) and held by a substrate holder, and then the temperature of the substrate 11 is raised to about 1000 ° C and the surface of the substrate 11 is cleaned by introducing a nitrogen gas and hydrogen gas stream.

The substrate temperature is lowered to about 550 ° C and then nitrogen gas is introduced as a carrier gas and ammonia, NH ₃ , and trimethyl gallium (TMG) are supplied to form a buffer layer 12 on the surface of the substrate 11 .

The TMG supply to the reaction chamber is adjusted once and the substrate temperature is raised to about 1050 ° C., and a p-type nitride semiconductor layer 13 made of GaN doped with Mg, which is a p-type dopant, is placed on the buffer layer 12 grown by adding ammonia, NH ₃ , TMG and bicyclopentadienyl magnesium (Cp ₂ Mg) while introducing nitrogen gas and hydrogen gas as a carrier gas.

The supplies of TMG and Cp ₂ Mg to the reaction chamber are set and then the substrate 11 is cooled from 1050 ° C to 700 ° C, the ambient flow of nitrogen gas, hydrogen gas and ammonia gas, NH ₃ , is maintained. Thereafter, the supply of hydrogen gas and ammonia, NH ₃ , is set and the substrate 11 is cooled below 100 ° C, the nitrogen gas flow being maintained as the ambient gas.

The process for producing a p-type nitride Semiconductor in embodiment 3 is characterized by that the p-type nitride semiconductor layer in the cooling process while about 950 ° C - about 700 ° C substrate temperature under egg ner combination of the hydrogen concentration in the atmosphere right and the cooling time at which the deactivation tion hardly occurs in the p-doping material. Another Be writing follows in this regard.

Regarding the cooling process, which is based on a p-type nit rid semiconductor is to be applied after being on a substrate temperature of about 950 ° C or higher, fan the inventors of the present invention derived the fact that the hole carrier density in the p-type nitride Semiconductors specifically over a temperature range of approximately 950 ° C - about 700 ° C substrate temperature due to the environment existing oxygen is reduced.

Fig. 5 is a graph showing the dependency of the hole carrier density in Embodiment 3 on the holding temperature for the substrate during the cooling process. The respective temperatures shown in the graph represent a temperature at which a substrate which carries a magnesium-doped GaN layer formed at a substrate temperature of 1050 ° C. is held for 10 minutes during the cooling process, before it is cooled to room temperature; the horizontal axis represents the substrate temperature at which it is held for 10 minutes, while the hole carrier density is plotted on the vertical axis. The atmosphere for the cooling process was created with a concentration of ammonia, NH ₃ , of 20% in nitrogen base in two versions with different hydrogen concentrations, 30% and 0%. As shown in Fig. 5, in the case of a hydrogen concentration of 30%, the hole carrier density decreases significantly at temperatures between 950 ° C-700 ° C, the lowest being about 800 ° C. The case of 0% hydrogen concentration also shows similar tendencies at the same temperatures, but the amount of decrease was less. It has been clarified that the hole carrier density in a p-type nitride semiconductor decreases in accordance with the concentration of hydrogen present in the atmosphere in the temperature range 950 ° C.-700 ° C. It is believed that the decrease in hole carrier density was caused by a p-type dopant contained in the p-type nitride semiconductor, which p-type dopant is deactivated as a result of coupling with hydrogen. The slight drop, which even occurred at 0% hydrogen concentration, appears to have been caused by hydrogen generated from decayed ammonia, NH ₃ .

Furthermore, the relationship between the hole carrier density was also and the cooling time examined in the cooling process for Sen ken the substrate temperature from about 950 ° C to about 700 ° C ge was taken.

Fig. 6 is a graph showing the dependency of the hole carrier density in Embodiment 3 on the cooling time for the substrate, which was taken in the cooling process to lower from about 950 ° C to about 700 ° C. It was namely with Mg-doped GaN layers, which were formed at substrate temperatures of 1050 ° C, at various cooling speeds to 700 ° C and then cooled to room temperature; the horizontal axis represents the cooling time taken for lowering the substrate temperature from approximately 950 ° C. to approximately 700 ° C., while the hole carrier density is plotted on the vertical axis. The cooling rate was controlled to be substantially constant at least during the substrate temperature range from about 950 ° C to about 700 ° C. The atmosphere for the cooling process was created with a concentration of ammonia, NH ₃ , of 20% in nitrogen base in four versions with different hydrogen concentrations, 50%, 30%, 10% and 0%. As can be seen in FIG. 6, the hole carrier density decreased with the extension of the cooling time in all cases with different hydrogen concentrations. It was calculated from Figure 6, the cooling time that was required so that the hole carrier density at room temperature was about 1 × 10 ¹⁶ cm ^-3 ; the results were: 1.0 min, 1.8 min, 4.1 min and 15 min for the 50%, 30%, 10% and 0% hydrogen concentrations, respectively. Namely, to ensure the value of about 1 × 10 ¹⁶ cm ^-3 or higher, which is the requirement because it is a practical p-type semiconductor, it has been found that the cooling time for lowering the substrate temperature is about 950 ° C to about 700 ° C for the cases of hydrogen concentrations of 50%, 30%, 10% and 0% must be within 1.0 min, 1.8 min, 4.1 min and 15 min, respectively.

Fig. 7 is a graph showing the relationship between the hydrogen concentration in the atmosphere of the cooling time for the substrate, which is taken for a decrease from about 950 ° C to about 700 ° C during the cooling process in a process for producing a p -conductive nitride semiconductor according to an embodiment of the present invention shows.

Based on the above results, it can be seen that the combinations of the hydrogen concentration in the atmosphere and the cooling time, among which combinations the deactivation of a p-type dopant is difficult to occur, during the cooling process for the substrate from about 950 ° C to about 700 ° C , which comes after a p-type semiconductor is formed, should fall into an area shown in FIG. 7; in a coordinate (X, Y), in which the X axis represents the hydrogen concentration (%) in the atmosphere, while the Y axis represents the cooling time (min), which is used to cool a substrate from approximately 950 ° C. is taken to about 700 ° C, the area is shown by an area surrounded by points ABCDEF, with point A (50, 1.0), point B (30, 1.8), point C ( 10, 4.1), point D (0, 5), point E (0, 0.5) and point F (50, 0.5). The reason why the lowest limit of the cooling time regardless of the hydrogen concentration is specified by a straight line EF of 0.5 min is that if it is cooled in a shorter cooling time than this, the p-type nitride semiconductor in There is a risk of being damaged by cracks caused by thermal shock.

(Embodiment 4)

Similar to Embodiment 3, a p-type nitride semiconductor having the structure of FIG. 1 is manufactured by a method according to a fourth exemplary embodiment of the present invention.

First, in the same manner as in Embodiment 3, a buffer layer 12 and a p-type nitride semiconductor layer 13 are formed on a substrate 11 in order as shown in FIG. 1.

In the process for producing a p-type nitride Semiconductor in embodiment 4, the p-type nitride Semiconductor layer when the substrate temperature is close of about 800 ° C, under a combination of water concentration of substances in the atmosphere and the cooling rate cooled down in which the deactivation at the p- Doping material hardly occurs.  

As can be seen in FIG. 5, the deactivation of the p-dopant occurs most clearly when the substrate temperature is approximately 800 ° C. in a range between approximately 950 ° C. and approximately 700 ° C. In order to maintain the property of the low resistivity of a p-type nitride semiconductor, it is effective to make the moving time of the substrate near 800 ° C as short as possible. In other words, the cooling rate at around 800 ° C should be faster than specified.

From Fig. 6, it can be seen that, in order to ensure the value of about 1 × 10 ¹⁶ cm ^-3 or higher, which is a requirement for it to be a practical p-type semiconductor, the cooling rate is close to one Sub strate temperature of about 800 ° C for the cases of a hydrogen concentration of 50%, 30%, 10% and 0% 250 ° C / min, 140 ° C / min, 61 ° C / min or 17 ° C / min or must be more.

Fig. 8 is a graph showing the relationship between the hydrogen concentration in the atmosphere and the cooling rate of the substrate lung near 800 ° C during the cooling process in a method for the manufacture of a p-type nitride semiconductor according to a fourth exemplary embodiment of the present invention.

Based on the above results, it can be determined that the combinations of the hydrogen concentration in the atmosphere and the cooling rate, under which combinations, the deactivation of a p-type dopant is difficult at a substrate temperature of 800 ° C. during the cooling process that comes after a p-type semiconductor is formed, should fall within a range shown in Fig. 8; in a coordinate (X, Y) where the X axis represents the hydrogen concentration (%) in the atmosphere, while the Y axis represents the cooling rate (° C / min) near a substrate temperature of 800 ° C the area is shown by an area surrounded by points OPQRST, where point O (50, 250), point P (30, 140), point Q (10, 61), point R (0, 17), point S (0, 500) and point T (50, 500). The reason why the upper limit of the cooling rate for the hydrogen concentration is irrelevant specified by a straight line ST at 500 ° C / min is that if it is cooled at a higher cooling rate than this, a p-type nitride Semiconductors are at risk of being damaged by cracks due to thermal shock.

In addition to sapphire, the substrate 11 can be made of various materials other than the nitride semiconductor, such as SiC, spinel, Si, GaAs, etc. It can also consist of GaN or other nitride semiconductor materials. In a case where the substrate 11 is made of such a different material, a buffer layer 12 made of GaN, etc., is deposited at a low substrate temperature of about 400 ° C - about 600 ° C between the substrate 11 and the p- conductive nitride semiconductor layer 13 is formed in the order to reduce the lattice offset between the nitride semiconductor and the substrate 11 . In a case where the substrate 11 is made of a nitride semiconductor, a p-type nitride semiconductor layer can be formed directly on the substrate 11 without providing a buffer layer 12 .

The p-type nitride semiconductor layer 13 may be provided on a substrate 11 on which an n-type nitride semiconductor layer and an active layer of a nitride semiconductor are formed in advance. The layer structure of a device with a pn junction can thus be formed.

The p-type nitride semiconductor layer 13 is formed by introducing the sources of a p-type dopant, nitrogen and sources for group III while maintaining the substrate temperature 11 at about 950 ° C or higher. A preferred temperature range for the substrate is about 950 ° C - about 1200 ° C. If the substrate temperature is below 950 ° C., during the formation of the p-type nitride semiconductor layer 13, the p-type dopant easily couples with hydrogen, making it inactive. This makes it difficult to form a p-type nitride semiconductor layer having a low resistivity. If the substrate temperature is higher than 1200 ° C, it becomes difficult to form a p-type nitride semiconductor layer with better crystal properties.

The p-type nitride semiconductor layer 13 can be provided in the form of a single layer made of GaN, AlGaN, InGaN, InAlGaN etc. or by arranging some of these layers one above the other. Of these, Al _x Ga _1-x N (0 = x <1), which provides a better crystal property at a substrate temperature of about 950 ° C or higher, or this, doped with a very small amount of In, is preferred.

For the p-type dopant for the p-type nitride semiconductor layer 13 , Mg, Zn, Cd, C, etc. can be used. Of these, Mg is preferred, with which the p-line is made relatively readily available. The concentration of the p-type dopant should preferably be not less than 1 × 10 ¹⁹ cm ^-3 and not more than 5 × 10 ²⁰ cm ^-3 . When the concentration of p-type dopant is less than 1 × 10 ¹⁹ cm ^-3 , the hole carrier density of the p-type nitride semiconductor layer 13 becomes low and the ohmic contact resistance becomes high when an electrode is formed on the p-type nitride semiconductor layer 13 is trained. If it is higher than 5 × 10 ²⁰ cm ^-3 , the crystal property of the p-type nitride semiconductor layer 13 deteriorates due to the fact that the p-type dopant has been doped to a high concentration, making it difficult to To get lead.

As for the atmosphere in a reaction chamber for forming the p-type nitride semiconductor layer 13 , it is preferable that it contains hydrogen in a concentration of 5% -70%, more preferably in a concentration of 10% -30%. If the concentration is less than 5%, the crystal property of the p-type nitride semiconductor layer 13 deteriorates due to reduced atomic migration at the surface for the formation and the speed at which the p-type dopant enters the p-type Nitride semiconductor layer 13 is recorded, decreases. If the concentration exceeds 70%, the p-type dopant is deactivated by hydrogen during the formation of the p-type nitride semiconductor layer 13 .

During the cooling process, the concentration of ammonia, NH ₃ , in the atmosphere should preferably be kept at 5% or more, at least at the time when the substrate temperature becomes lower than 950 ° C. If the concentration is below 5%, nitrogen easily separates from the surface of the p-type nitride semiconductor, which tends to result in deteriorated crystal property on the surface.

Also, during the cooling process, the concentration of ammonia, NH ₃ , in the atmosphere during the time when the substrate temperature is about 950 ° C - about 700 ° C should preferably be 30% or less. If it is higher than 30%, the hole carrier density in the p-type nitride semiconductor decreases slightly due to the increased hydrogen generated as a result of thermal decomposition of ammonia, NH ₃ .

CONCRETE EXAMPLE

Now the process for producing a p- conductive nitride semiconductor of the present invention concrete examples with reference to the drawings wrote.  

(Concrete example 1)

A p-type nitride semiconductor was manufactured, the cross-sectional structure of which is shown in FIG. 1.

First, a substrate 11 having a mirror-finished main surface was placed in a reaction chamber (not shown) and held by a substrate holder, and then the temperature of the substrate was raised to about 1000 ° C and nitrogen gas at 5 l / min, hydrogen gas with 5 L / min introduced while the substrate was heated for about 10 minutes. Thus, stains of organic matter and moisture adhering to the main surface of the substrate 11 were removed.

The substrate temperature was reduced to about 550 ° C and then nitrogen gas as carrier gas with a throughput of about 16 l / min and ammonia, NH ₃ , with a throughput of about 4 l / min, TMG with a throughput of about 40 µmol / min introduced in order to form a buffer layer 12 made of GaN on the surface of the substrate 11 to a thickness of approximately 0.03 μm.

The TMG feed to the reaction chamber was adjusted once and the substrate temperature was raised to approximately 1050 ° C. and a 2 μm thick p-type nitride semiconductor layer 13 made of GaN, which was doped with Mg, a p-doping material, was deposited on the buffer layer 12 , grown by nitrogen gas with a throughput of about 12 l / min, hydrogen gas with a throughput of about 4 l / min as carrier gas and ammonia, NH ₃ , with a throughput of about 4 l / min, TMG with a throughput of about 80 µmol / min and Cp ₂ Mg with a throughput of about 0.2 µmol / min was introduced. The Mg concentration in the p-type nitride semiconductor was approximately 2 × 10 ¹⁹ cm ^-3 . The throughput of hydrogen gas includes the hydrogen gas required to vaporize the TMG and the Cp ₂ Mg.

The supply of TMG and Cp ₂ Mg to the reaction chamber was turned on and then the substrate 11 was cooled from 1050 ° C to 950 ° C in about 0.5 min while nitrogen gas with a throughput of about 12 l / min, hydrogen gas with a Through rate of about 4 l / min and ammonia, NH ₃ , with a flow rate of about 4 l / min were introduced as the ambient gas.

And then the hydrogen gas was adjusted and nitrogen gas was supplied as the ambient gas at a flow rate of about 16 l / min, ammonia, NH ₃ , at a flow rate of about 4 l / min, while the temperature of the substrate 11 was about 1.2 min was reduced from 950 ° C to 700 ° C. The cooling speed for the substrate 11 near 800 ° C was about 210 ° C / min. Thereafter, the supply of ammonia, NH ₃ , was stopped and nitrogen gas was continued to flow as the ambient gas at a flow rate of about 20 l / min left until the substrate temperature became less than 100 ° C.

After the cooling was completed, the substrate 11 provided with the p-type nitride semiconductor layer 13 was taken out of the reaction chamber. The substrate 11 was separated into individual chips of 5 mm square without undergoing post-annealing. The Hall effect of the chip was measured by the Van der Pauw method; the result showed that the hole carrier density was 1.6 × 10 ¹⁷ cm ^-3 and there was a better p-type semiconductor layer with a low specific resistance. The hole carrier density of the p-type nitride semiconductor layer 13 before cooling was estimated to be approximately 2.0 × 10 ¹⁷ cm ^-3 as a result of an extrapolation of the cooling time from zero in FIG. 6. As a result, the decrease in hole carrier density was suppressed within about 20% during the cooling process.

(Concrete example 2)

A p-type nitride semiconductor of the present example 2 was prepared in the same procedure as in Example 1  except that the conditions of the atmosphere during the Cooling process were modified.

Practically, after the p-type semiconductor layer 13 was formed, the supply of TMG and Cp ₂ Mg to the reaction chamber was stopped, and then the substrate 11 was cooled from 1050 ° C to 700 ° C in about 1.7 minutes while nitrogen gas with a throughput of about 12 l / min, hydrogen gas with a throughput of about 4 l / min and ammonia, NH ₃ , with a throughput of about 4 l / min as ambient gas. It took about 0.5 minutes for the temperature of the substrate 11 to come down from 1050 ° C. to 950 ° C., and about 1.2 minutes from 950 ° C. to 700 °. The cooling rate for the substrate 11 in the vicinity of 800 ° C. was approximately 210 ° C./min,

After the temperature of the substrate 11 became lower than 700 ° C, the supply of hydrogen gas and ammonia, NH ₃ , was stopped and nitrogen gas was allowed to continue flowing as an ambient gas at a flow rate of about 20 l / min until the substrate temperature was lower than 100 ° C.

After the cooling was completed, the substrate 11 provided with the p-type nitride semiconductor layer 13 was taken out of the reaction chamber. The substrate 11 was separated into individual 5 mm square chips. The Hall effect of the chip was measured. The result of the measurement showed that the hole carrier density was about 4.6 × 10 ¹⁶ cm ^-3 . The hole carrier density of the p-type nitride semiconductor layer 13 before cooling was assumed to be approximately 2.0 × 10 ¹⁷ cm ^-3 . As a result, the decrease in the positive hole carrier density during the cooling process was suppressed within about 77%.

(Comparative Example 1)

A p-type nitride semiconductor of the present ver same example 1 was in the same procedure as in the con creten Example 2, except that the cooling time  (or speed) modified during the cooling process were.

Practically, after the p-type semiconductor layer 13 was formed, the supply of TMG and Cp ₂ Mg to the reaction chamber was stopped, and then the substrate 11 was cooled from 1050 ° C to 700 ° C in about 5.6 minutes while nitrogen gas with a throughput of about 12 l / min, hydrogen gas with a throughput of about 4 l / min and ammonia, NH ₃ , with a throughput of about 4 l / min as ambient gas. It took about 1.6 minutes for the temperature of the substrate 11 to come down from 1050 ° C. to 950 ° C., and about 4.0 minutes from 950 ° C. to 700 °. The cooling rate for the substrate 11 near 800 ° C was about 63 ° C / min.

After the temperature of the substrate 11 became lower than 700 ° C, the supply of hydrogen gas and ammonia, NH ₃ , was stopped and nitrogen gas was allowed to continue flowing as an ambient gas at a flow rate of about 20 l / min until the substrate temperature was lower than 100 ° C.

After the cooling was completed, the substrate 11 provided with the p-type nitride semiconductor layer 13 was taken out of the reaction chamber. The substrate 11 was separated into individual 5 mm square chips. The Hall effect of the chip was measured. The result of the measurement showed that the hole carrier density was approximately 2 × 10 ¹⁵ cm ^-3 , a higher specific resistance.

The hole carrier density of the p-type nitride semiconductor layer 13 before cooling was assumed to be approximately 2.0 × 10 ¹⁷ cm ^-3 . As a result, the hole carrier density decreased by about 99% during the cooling process.

(Concrete example 3)

Fig. 9 is a cross-sectional view of another exemplary embodiment showing the construction of a p-type nitride semiconductor according to the present invention.

In the present concrete example, a light-emitting device with nitride semiconductor from FIG. 9 was produced, in which a p-type nitride semiconductor layer was arranged at the top.

The light-emitting device with nitride semiconductor comprises a first n-type cladding layer 22 made of undoped GaN, a second n-type cladding layer 23 made of undoped AlGaN, a light-emitting layer 24 made of undoped InGaN and an intermediate layer 25 made of not doped GaN and a p-type plating layer 26 made of Mg-doped AlGaN, which are arranged one above the other on a substrate 21 made of Si-doped n-type GaN. On the p-type plating layer 26, there is a p-electrode 27 made of Pt and Au which is arranged in order, while an n-electrode 28 is made of Ti and Au which is arranged on the exposed area of the substrate 21 , Thus, the present light emitting device is a light emitting diode which forms a pn junction therebetween with the light emitting layer 24 .

In the following, a method for producing the light diodes or described with the above configuration.

First, a substrate 21 made of GaN doped with Si to provide an n property and having a mirror-polished surface was placed in a reaction chamber (not shown) and held by a substrate holder. The temperature of the substrate 21 was raised to about 1100 ° C and the substrate 21 was heated for about 1 minute while nitrogen gas at a flow rate of 4 l / min, hydrogen gas at a flow rate of 4 l / min and ammonia, NH ₃ , with a throughput of 2 l / min the substrate 21 was supplied. This removed stains from organic matter and moisture adhering to the surface.

The substrate temperature was kept at about 1,100 ° C. and nitrogen gas with a throughput of about 13 l / min, hydrogen gas with a throughput of about 3 l / min as carrier gas and ammonia, NH ₃ , with a throughput of about 4 l / min min, TMG introduced with a throughput of about 80 µmol / min to form the first n-type plating layer 22 made of undoped GaN to a thickness of 0.5 µm.

After the first n-type plating layer 22 was formed, the temperature of the substrate 21 was kept at about 1050 ° C and became nitrogen gas with a flow rate of about 15 l / min, hydrogen gas with a flow rate of about 3 l / min as carrier gas and ammonia , NH ₃ , with a throughput of about 2 l / min, TMG with a throughput of about 40 µmol / min and trimethylaluminum (TMA) with a throughput of about 3 µmol / min to a 0.05 µm thick second n- to form conductive plating layer 23 of undoped Al _0.05 Ga _0.95 N.

After the second n-type plating layer 23 was formed, the supply of TMG and TMA was stopped, the temperature of the substrate 21 was lowered to about 700 ° C. and kept at this level. Nitrogen gas with a throughput of about 14 l / min, ammonia, NH ₃ with a throughput of about 6 l / min, TMG with a throughput of about 4 µmol / min and trimethylindium (TMI) with a throughput of about 1 were used as carrier gas µmol / min introduced to form a SQW light-emitting layer 24 of _undoped In _0.15 Ga _0.85 N up to a thickness of about 0.002 µm.

After the light emitting layer 24 was grown, the supply of TMI was stopped and became nitrogen gas as a carrier gas with a flow rate of about 14 l / min and ammonia, NH ₃ , with a flow rate of 6 l / min, TMG with a flow rate of Allow 2 µmol / min to flow onto the substrate 21 , the substrate temperature being increased to 1050 ° C. In this way, the intermediate layer 25 was formed from undoped GaN to a thickness of 0.004 μm.

After the temperature of the substrate 21 reached 1050 ° C, nitrogen gas with a flow rate of about 14 l / min, hydrogen gas with a flow rate of about 4 l / min as carrier gas and ammonia, NH ₃ , with a flow rate of 2 l / min , TMG with a throughput of 40 µmol / min, TMA with a throughput of 3 µmol / min and Cp ₂ Mg with a throughput of 0.4 µmol / min were introduced to a p-type plating layer 26 made of Mg-doped Al _0.05 Ga _0.95 N to a thickness of 0.2 microns. The Mg concentration in the p-type platier layer was approximately 8 × 10 ¹⁹ cm ^-3 .

After the p-type plating layer 26 was grown, the supply of TMG, TMA and Cp ₂ Mg was decreased, and the temperature of the substrate 21 was lowered from 1050 ° C to 950 ° C in about 0.5 min while nitrogen gas was supplied with a Throughput of about 14 l / min, hydrogen gas with a throughput of about 4 l / min and ammonia, NH ₃ , with a throughput of about 2 l / min as ambient gas were introduced.

The supply of the hydrogen gas was stopped and then the temperature of the substrate 21 was lowered from 950 ° C to 700 ° C in about 1.2 minutes, while nitrogen gas with a throughput of about 18 l / min, ammonia, NH ₃ , with a Throughput of about 21 / min were supplied as the ambient gas. The cooling rate for the substrate 21 near 800 ° C was about 210 ° C / min. After the temperature of the substrate 21 became lower than 700 ° C, the supply of ammonia, NH ₃ , was stopped while nitrogen gas as Ambient gas was allowed to continue to flow at a flow rate of about 20 l / min until the temperature of the substrate 21 became less than 100 ° C. Then the substrate 21 was taken out of the reaction chamber.

The nitride semiconductor layers thus provided, including the p-type cladding layer 26 , proved themselves to be better p-type semiconductor layers with low resistivity without going through the post-annealing process to activate the doped Mg.

Next, an SiO ₂ layer was deposited over the surface of the nitride semiconductor with a thus formed structure of layers arranged one above the other by a CVD process without using any post-annealing. A rectangular pattern was provided thereon by photolithography and a wet etching process, and an etching mask made of SiO _{2 was} formed. Using a reactive ion etching process, the p-type plating layer 26 , the intermediate layer 25 , the light emitting layer 24 , the second n-type plating layer 23 , the first n-type plating layer 22 and a part of the substrate were in one layer device removed in the opposite direction to the stacking direction until the substrate 21 was etched away to a depth of approximately 1 μm. Thus, the surface of the substrate 21 was partially exposed. On part of the exposed surface of the substrate 21 , an n-electrode 28 was formed by stacking 0.1 µm thick Ti and 0.5 µm thick Au by photolithography and evaporation. After removing the etching mask from SiO ₂ by a wet etching process, a p-electrode 27 consisting of 0.3 μm thick Pt and 0.5 μm thick Au, which covered most of the surface of the p-type plating layer 26 , was used the photolithography and an evaporation process provides. The thickness of the substrate 21 was adjusted to a thickness of 100 μm by grinding the back and then cut into individual chips by cutting.

Thus, in the structure as shown in Fig. 9, a light-emitting device with nitride semiconductor was provided.

The light emitting device was attached with the electrodes of the chip down to an Si diode on which a pair of positive and negative electrodes are provided. They are connected by an Au hump. The light emitting device was attached so that the p-electrode 27 and the n-electrode 28 are connected to the negative electrode and the positive electrode of the Si diode. Then, the Si diode carrying the light emitting device was attached to a base using Ag paste, the positive electrode of the Si diode was connected with a wire to an electrode on the base, and then molded with a resin to make a finished one To provide LED. The light-emitting diode was operated with a current in the forward direction of 20 mA and it emitted blue light with a peak wavelength of 470 nm, showing a uniform light radiation from the back of the substrate 21 . The light output was 4 mW, the operating voltage in the forward direction was 3.4 V.

As described above, in the present concrete example, a p-type semiconductor layer having a low specific resistance and better quality than the p-type plating layer 26 was formed and in the process of forming the p-type nitride semiconductor layer; and it can be cooled in the cooling process while maintaining the low resistivity property of the p-type plat layer 26 . As a result, a nitride semiconductor light emitting device that operates at a low voltage and performs well is made available without requiring any post-annealing treatment or other such specific processing.

In a process for producing a p-type nitride Semiconductor of the present invention is based on a sub strat a low p-type nitride semiconductor layer resistivity in an atmosphere that Hydrogen to a certain specific degree holds, in which the deactivation of a p-dopant well un can be suppressed; and will the p- conductive nitride semiconductor layer in a certain speci fish cooling time or atmosphere cooled so that the Hole carrier density of the p-type nitride semiconductor layer in decreases in a way in which the property of the low resistivity is pretty much maintained. As he The result is a p-type nitride semiconductor with a special made available its crystal properties without ir an after-heat treatment is needed.

In a process for producing a p-type nitride Semiconductor of the present invention is based on a sub Strat a p-type nitride semiconductor layer is formed and the p-type nitride semiconductor layer during ei certain specific substrate temperature range in the Ab cooling process under a certain specific combination of hydrogen concentration in the atmosphere and cooling time or hydrogen concentration in the atmosphere and cooling speed cooled, under which combination the p- Doping material is hardly deactivated. As a result, a P-type nitride semiconductor with low specific Wi resistance and better crystal quality available makes without any post-treatment or a other such specific processing is needed.

Furthermore, in the method of the present invention, the Manufacturing process for the p-type nitride semiconductor be simplified so that the cost of manufacture  a nitride semiconductor device having a p-type Includes nitride semiconductors can be reduced.

Claims (12)

1. A method for producing a p-type nitride semiconductor, which comprises:
a semiconductor layer forming process for forming a low resistivity p-type nitride semiconductor layer on a substrate maintained at a temperature of 600 ° C or more by a source of a p-type dopant, a nitrogen source and a source of Group III are guided to the substrate, and
a cooling process for cooling the substrate carrying the p-type nitride semiconductor layer; in which the hole carrier density of the p-type nitride semiconductor layer decreases during the cooling process. 2. Process for producing a p-type nitride A semiconductor according to claim 1, wherein the decrease rate of Hole carrier density is 0% -95%. 3. Process for producing a p-type nitride A semiconductor according to claim 1 or claim 2, wherein the Cooling process includes a procedure during which the Substrate within 30 min of the substrate temperature in the process of forming a semiconductor layer to 600 ° C is cooled. 4. Process for producing a p-type nitride Semiconductor according to claim 1, 2 or 3, wherein the Atmo sphere in the process forming a semiconductor layer Contains 5-70 vol .-% hydrogen. 5. Process for producing a p-type nitride Semiconductor according to claim 1, 2 or 3, in which the sel During the procedure- introduced atmosphere in the cooling process for cooling a substrate from a substrate temperature  structure in the process forming a semiconductor layer 600 ° C contains about 5-50 vol .-% hydrogen. 6. A method for producing a p-type nitride semiconductor according to claim 1, 2 or 3, wherein the atmosphere introduced during the procedure in the cooling process for cooling a substrate from the substrate temperature in the process forming a semiconductor layer to 600 ° C ammonia, NH ₃ , contains. 7. A method for producing a p-type nitride semiconductor, which comprises:
a process of forming a p-type nitride semiconductor layer to form a low-resistivity p-type nitride semiconductor layer on a substrate held at a temperature of 950 ° C. or more by using a source of a p-type dopant, a nitrogen source and a group III source are applied to the substrate, and
a cooling process for cooling the substrate carrying the p-type nitride semiconductor layer; in which the substrate is cooled in the cooling process during a procedure for cooling the substrate from approximately 950 ° C. to approximately 700 ° C. under certain specific combinations of the hydrogen concentration in the atmosphere and the cooling time, in which the p-type nitride semiconductor layer has the property of can maintain low resistivity. 8. Process for producing a p-type nitride The semiconductor of claim 7, wherein the combination of the hydrogen concentration in the At atmosphere and the cooling time falls in an area that by points A-B-C-D-E-F in an X-Y- Coordinate can be specified with the X axis represents the hydrogen concentration (%) in the atmosphere and the Y axis represents the cooling time (min),  in which point A (50, 1.5), point B (30, 1.8), point C (10, 4.1), point D (0, 15), point E (0, 0.5) and point F (50, 0.5). 9. A method for producing a p-type nitride semiconductor, which comprises:
a process of forming a p-type nitride semiconductor layer to form a low-resistivity p-type nitride semiconductor layer on a substrate held at a temperature of 950 ° C. or more by using a source of a p-type dopant, a nitrogen source and a group III source are applied to the substrate, and
a cooling process for cooling the substrate carrying the p-type nitride semiconductor layer; in which the substrate is cooled in the vicinity of about 800 ° C under certain specific combinations of the hydrogen concentration in the atmosphere and the cooling rate, in which the p-type nitride semiconductor layer can maintain the property of low specific resistance. 10. Process for producing a p-type nitride The semiconductor of claim 9, wherein the combination of the hydrogen concentration in the At atmosphere and the cooling time falls in an area that by points O-P-Q-R-S-T in an X-Y- Coordinate can be specified with the X axis represents the hydrogen concentration (%) in the atmosphere and the Y axis represents the cooling rate (° C / min) in which point O (50, 250), point P (30, 140), point Q (10, 61), point R (0, 17), point S. (0, 500) and point T (50, 500). 11. p-type nitride semiconductor on a substrate grown at a temperature of 600 ° C or higher is, in which the hole carrier density immediately after the Ab  cooling process equal to about 5% -100% of the density of the perforated beams at the growing temperature. 12. p-type nitride semiconductor on a substrate grown at a temperature of 600 ° C or higher with the top of the p-type nitride Semiconductor is exposed, in which the hydrogen concentration near the top of the p-type nitride semiconductor is equal to 1- to 10 times that inside the p-type nitride Is semiconductor.