JP4752394B2 - N-type nitride semiconductor electrode and method of forming n-type nitride semiconductor electrode - Google Patents

Description

  The present invention relates to an electrode structure of a semiconductor device using a nitride material and a method for forming the same.

Nitride-based semiconductors such as GaN, AlGaN, InGaN, and InAlGaN have a wide band gap of 1.95 to 6 eV, particularly a large band gap of 3 eV or more, and thus are promising as blue to ultraviolet light emitting materials. Blue laser diodes have been put into practical use. Also, it has a high breakdown field strength, a high thermal conductivity, a high electron saturation rate, and a high two-dimensional electron gas concentration exceeding 1 × 10 ¹³ cm ⁻² at the AlGaN / GaN heterojunction interface is relatively Since it can be easily obtained, it is regarded as promising as a high-frequency power device material and has been actively developed.

  For manufacturing these devices, an electrode that forms an ohmic contact with an n-type nitride semiconductor layer with a sufficiently low contact resistance is required. In the above-described field effect transistor using the two-dimensional electron gas at the AlGaN / GaN heterojunction interface as a channel, an ohmic electrode may be formed on the surface of the non-doped AlGaN layer to which no impurity is added. Since an ohmic contact is formed with respect to a layer containing a high concentration of electrons, an ohmic electrode is formed by the same structure and manufacturing method as those formed in the n-type nitride semiconductor layer. Here, the n-type nitride semiconductor and the ohmic electrode for the two-dimensional electron gas are both described as an n-type ohmic electrode (contact).

  Patent Document 1 discloses an electrode structure that forms a good ohmic contact with the surface of an n-type gallium nitride semiconductor. According to Patent Document 1, after forming a multilayer film in which titanium (Ti) and aluminum (Al) are laminated in this order on the surface of the n-type gallium nitride based semiconductor layer, annealing is performed, so that a part or all of the multilayer film is formed. It is said that a good ohmic electrode with low contact resistance can be formed by alloying.

Thus, the Ti / Al-based ohmic electrode is a good ohmic electrode with a very low contact resistance of 10 ⁻⁶ Ωcm ² or less by heat treatment at 400 to 1200 ° C., particularly high temperature heat treatment at a melting point of Al (660 ° C.) or higher. It is known that can be formed.

Non-Patent Document 1 describes a Schottky barrier of a semiconductor device.
Japanese Patent No. 2783349 Journal of Applied Physics Vol. 89, No. 1, pp. 425-429 (2001)

  However, this conventional n-type ohmic electrode has problems such as an increase in contact resistance and finally a disconnection in terms of long-term reliability. The reason is that Au is arranged in the very vicinity of Al that forms the n-type ohmic electrode in the heat treatment process for electrode formation, the assembly process to the package, the wire bonding process, etc. This is because an intermetallic compound of Al and Au called purple plague is formed by interdiffusion of electrode metal resulting from high current density when the device is used.

  For example, in order to obtain a low contact resistance as described above, when a high temperature heat treatment at a melting point of Al (660 ° C.) or higher is performed, the surface morphology of the electrode is deteriorated and the electrode edge is disturbed. Is covered with an electrode containing a metal having a high melting point and Au to prevent a problem of the electrode due to heat treatment, and by making the electrode containing Au, an effect of reducing the resistance of the electrode itself can be obtained. The electrode material used as the cover here should be a two-layer structure such as Mo / Au, Pt / Au, Ni / Au, Ti / Au, Nb / Au, or a multilayer structure such as Mo / Pt / Au. There is also. A refractory metal provided between Au and Al, such as Mo, Pt, Ni, Ti, and Nb, acts as a barrier to prevent contact between Au and Al to some extent, but these metals are at most several tens of nanometers to several tens of nanometers. Since it is formed with a thickness of 100 nm, it is difficult to completely prevent the contact between Au and Al under a high temperature heat treatment exceeding the melting point of Al or under a condition where a high current density flows when the device is used.

  Even when a cover electrode containing Au is not used, Au is a chemically stable metal that is resistant to oxidation and corrosion. Therefore, when mounting a device chip on a package, AuSn is used as a solder material. Generally, an alloy is used and Au is used as a bonding wire. Since the n-type ohmic electrode containing Al is connected to any of these, it is difficult to avoid Au being disposed in the vicinity of Al.

The problem of intermetallic compounds called purple plague in Al-Au junction is formed _is in the _{Au 2 Al, Au 5 A l2} , Au 4 more intermetallic compounds such as Al is formed, for example, Au ₂ Al has a property of high electrical resistance and mechanically fragile, and Au ₅ Al ₂ and Au ₄ Al have different coefficients of thermal expansion, so that the bonding strength may be reduced at the interface between the two. Are known. As described above, in the Al—Au alloy system, a plurality of intermetallic compounds having different properties are formed, thereby causing problems such as generation of voids, increase in contact resistance, and eventually disconnection.

On the other hand, in order to avoid the above-mentioned problems related to the Al—Au junction, a structure not including Al has been studied as an n-type ohmic electrode, and Cr, Ni, In / Ti / Au, Sn / Ti / Au, etc. have been reported. However, it is difficult to obtain a low contact resistance of 10 ⁻⁶ Ωcm ² or less that can be obtained with a Ti / Al electrode.

  Therefore, the present invention has been made in view of the problems of the n-type ohmic electrode in the nitride-based semiconductor device described above, and its purpose is reliable for heat treatment in the manufacturing process and use conditions in which a high current flows. Another object of the present invention is to provide an n-type ohmic electrode that is excellent in properties and that provides a low contact resistance.

  The electrode structure of the present invention is an ohmic electrode formed on the surface of an n-type or non-doped nitride semiconductor, and Ti, Ta, Nb, Cr, V, Sn are formed in a first region in contact with the nitride semiconductor surface. , In, Zr, and Si, at least one kind of metal is contained, and Mg is contained in the second region formed thereon. The first region may contain Mg in addition to the configuration. A third region containing Au may be provided on the second region. Furthermore, usually, at least the first region and the second region are heat-treated to form an alloyed electrode.

  The n-type nitride semiconductor electrode forming method of the present invention is an ohmic electrode forming method formed on the surface of an n-type or non-doped nitride semiconductor, wherein Ti, Ta , Nb, Cr, V, Sn, In, Zr, and Si, a first layer containing at least one metal is formed, and Mg is formed on the first region. The ohmic electrode is formed by forming the first layer and heat-treating the first layer and the second layer. The first layer may contain Mg in addition to the above structure. Further, an ohmic electrode is formed by forming a third layer containing Au on the second layer containing Mg, and heat-treating the first layer, the second layer, and the third layer. May be formed.

By using the electrode structure according to the present invention, compared with a conventional Ti / Al-based n-type ohmic electrode, the heat treatment in the manufacturing process and the use conditions in which a high current flows are excellent in reliability, and 10 ^−6. It becomes possible to form a good n-type ohmic electrode having a low contact resistance of ² Ωcm or less.

Hereinafter, the reason why these effects can be obtained by the structure of the present invention will be described in detail. First, the effect of improving the reliability will be described. The problem of the conventional Al-containing electrode is caused by the formation of a plurality of intermetallic compounds having different properties such as Au ₂ Al, Au ₅ Al ₂ , and Au ₄ Al at the joint with Au as described above. there were. As can be seen from the phase diagram of the Al—Au alloy shown in FIG. 1, Au ₂ Al, Au ₅ Al ₂ , Au ₄ Al, and the like can exist stably at a relatively low temperature of 500 to 600 ° C. This is because it is an intermetallic compound. On the other hand, FIG. 2 shows a phase diagram of the Mg—Au alloy for Mg used in the present invention. It can be seen that the intermetallic compound that can stably exist at 600 ° C. or lower is Mg ₃ Au. That is, by using the n-type ohmic electrode according to the present invention, problems due to the formation of a plurality of intermetallic compounds occurring in the Al—Au system can be avoided, so that the reliability is higher than that of the conventional Ti / Al-based n-type ohmic electrode. It is possible to form an electrode having excellent properties.

Next, the low contact resistance of the n-type ohmic electrode according to the present invention will be described. First, the reason why a conventional Ti / Al-based n-type ohmic electrode has a lower contact resistance than other material systems will be considered. As described above, in this system, a good ohmic electrode having an extremely low contact resistance of 10 ⁻⁶ Ωcm ² or less is formed by heat treatment at 400 to 1200 ° C., particularly heat treatment at a temperature higher than the melting point of Al (660 ° C.). It is known that it can be done. This is because Ti is a metal that easily binds to N, and the Al Schottky barrier against an n-type nitride semiconductor is low. First, Ti and N in contact with the surface of the nitride-based semiconductor are bonded by the heat treatment, and a state where N is removed from the nitride-based semiconductor near the interface, that is, a large amount of N vacancies are formed. Since these N vacancies function in the same manner as donors (n-type impurities) in nitride-based semiconductors, there is a region (n ⁺ -type region) in which a large amount of n-type impurities are added near the interface between Ti and the nitride-based semiconductor. As a result, it functions to lower the contact resistance with the n-type ohmic electrode. In addition, Al is melted and rapidly moved by the heat treatment not lower than the melting point of Al and can reach the n ⁺ -type region. Since Al has a low Schottky barrier against n-type GaN of 0.60 eV (see Non-Patent Document 1, Table 1), Al is a metal that easily forms an ohmic contact with an n-type nitride-based semiconductor, and n ⁺ A good ohmic electrode with low contact resistance can be formed by contacting Al with the mold region.

  From this, the condition necessary to obtain an ohmic electrode having a low contact resistance with respect to the n-type nitride semiconductor is firstly coupled with N in the first region in contact with the surface of the n-type nitride semiconductor. Second, the second region formed on the first region is a metal that can quickly reach the n-type nitride semiconductor surface by heat treatment, that is, relatively There are three points: a metal having a low melting point is arranged, and third, a metal having a low Schottky barrier against the n-type nitride semiconductor is arranged in the second region.

Since the n-type ohmic electrode according to the present invention satisfies these conditions, an ohmic electrode having a low contact resistance can be obtained. That is, Ti, Ta, Nb, Cr, V, Sn, In, Zr, and Si arranged in the first region in contact with the n-type nitride-based semiconductor surface are all metals that easily bond to N. Satisfies one condition. Further, the metal disposed on the first region contains at least Mg. That is, Mg is a metal having a melting point of 650 ° C. and slightly lower than that of Al, and satisfies the second condition. Further, Mg has a Schottky barrier against n-type GaN of approximately 0.62 eV and Al (see Non-Patent Document 1, Table 1), and also satisfies the third condition. From the above, the n-type ohmic electrode according to the present invention has an extremely low contact resistance of 10 ⁻⁶ Ωcm ² or less by heat treatment at a temperature higher than 650 ° C. which is the melting point of Mg.

As described above, when the n-type ohmic electrode according to the present invention is used, the heat treatment in the manufacturing process is maintained while maintaining the extremely low contact resistance of 10 ⁻⁶ Ωcm ² or less obtained by the conventional Ti / Al based ohmic electrode. In addition, it is possible to form an ohmic electrode having excellent reliability with respect to use conditions in which a high current flows.

In the n-type ohmic electrode according to the present invention, Mg may be contained in the first region formed in contact with the surface of the n-type nitride semiconductor in addition to the above configuration. As a result of heat treatment as described above, Mg reaches the surface of the n-type nitride semiconductor, and Mg contacts the n ⁺ -type region formed on the surface of the n-type nitride semiconductor. By doing so, there is an effect that a lower contact resistance can be obtained.

  Further, a third region containing Au may be provided on the second region containing Mg. This has the effect of preventing deterioration of the surface morphology of the n-type ohmic electrode and disorder of the electrode edge due to heat treatment at a temperature higher than the melting point of Mg (650 ° C.), and is covered with an electrode containing Au. By doing so, there is an effect that it is possible to form a chemically stable n-type ohmic electrode in which oxidation and corrosion of the electrode hardly occur.

  The first effect is that there is no Au-Al reaction between Au and the n-type ohmic electrode, thus avoiding problems such as increased resistance, void generation, and disconnection that have occurred with conventional Ti / Al ohmic electrodes. In addition, an n-type ohmic electrode excellent in reliability and reproducibility can be obtained with respect to heat treatment in a manufacturing process and use conditions in which a high current flows.

The second effect is that the contact resistance of 10 ⁻⁶ Ωcm ² or less, which was difficult to realize without using a conventional Ti / Al-based ohmic electrode, can be realized with the n-type ohmic electrode according to the present invention. In addition, an n-type ohmic electrode having both low contact resistance and high reliability can be obtained.

  The third effect is that when the third region containing Au is provided on the region containing Mg, the surface morphology of the n-type ohmic electrode by the heat treatment at a temperature higher than the melting point of Mg (650 ° C.). It has the effect of preventing deterioration and disturbance of the electrode edge, and by covering with an electrode containing Au, it is possible to form a chemically stable n-type ohmic electrode that is unlikely to oxidize or corrode the electrode. Is to become.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
In the first embodiment, an n-type ohmic electrode according to the present invention is applied to a field effect transistor (FET) having an AlGaN / GaN heterojunction. FIG. 3 shows a cross-sectional structure of the manufactured field effect transistor. An AlN buffer layer 302 (0.2 μm), a non-doped GaN channel layer 303 (2.0 μm), a non-doped Al _0.25 Ga _0.75 N electron on the sapphire substrate 301 by using a metal organic chemical vapor deposition (MOCVD) method. After the supply layer 304 (0.025 μm) is epitaxially grown in this order, Ti / Mg / Mo / Au (film thickness 10/65/30 / thickness) is sequentially formed from the wafer surface by using a photolithography method, a vacuum deposition method and a lift-off method. 50 nm), and the wafers are heat-treated in a nitrogen gas atmosphere for 30 seconds using a RTA (Rapid Thermal Annealing) method to form ohmic source electrode 305 and drain electrode 306. did. By this heat treatment, the electrodes 305 and 306 are alloyed. Next, the element isolation region was mesa-etched using a photolithography method and a dry etching method. Further, a gate electrode 307 is formed between the source electrode 305 and the drain electrode 306 by depositing Ni / Au (film thickness 20/300 nm) in order from the wafer surface using a photolithography method, a vacuum evaporation method, and a lift-off method. Thus, a field effect transistor is completed. In Ti / Mg / Mo / Au, Ti is the first region (first layer) of the present invention, Mg is the second region (second layer) of the present invention, and Mo / Au is the first region of the present invention. This corresponds to the region 3 (third layer). In this embodiment, the source electrode 305 and the drain electrode 306 exhibiting ohmic properties are formed in order of Ti / Al / Mo / Au (thickness 10/60/30) from the wafer surface in order to compare with a conventional Ti / Al-based electrode. A field effect transistor having a laminated structure of / 50 nm) was also produced.

FIG. 4 shows the relationship between the contact resistance value of the ohmic electrode and the RTA heat treatment temperature measured using a TLM test pattern produced on the same wafer as the field effect transistor. It can be seen that good contact resistance of 10 ⁻⁶ Ωcm ² or less is obtained in the range of 750 to 950 ° C. even when any electrode structure of Ti / Mg / Mo / Au and Ti / Al / Mo / Au is used. .

  Next, using a field effect transistor manufactured at an RTA temperature of 850 ° C., which obtained the lowest contact resistance in the above-described experiment, an energization test for 200 hours under the conditions of an environmental temperature of 200 ° C., a drain voltage of 50 V, and a drain current of 100 mA / mm. Went. The current-voltage characteristics before and after the energization test when Ti / Mg / Mo / Au and Ti / Al / Mo / Au are used as the ohmic electrodes are shown in FIGS. 5 and 6, respectively. In a device using Ti / Al / Mo / Au, which is a conventional Ti / Al ohmic electrode, the drain current is greatly reduced, and the drain current rises slowly in the drain voltage <4 V region, so-called resistance. It has changed to a high state (FIG. 6). On the other hand, in the device using Ti / Mg / Mo / Au which is the ohmic electrode of the present invention, almost no change was observed in the current-voltage characteristics (FIG. 5).

As a result of detailed analysis of the contact resistance of each ohmic electrode, Ti / Mg / Mo / Au which is the ohmic electrode of the present invention has a contact resistance of 4.0 × 10 ⁻⁶ Ωcm ² before and after the energization test. 4.2 × 10 ⁻⁶ Ωcm ² , and the increase was about 5%, whereas in the conventional Ti / Al-based ohmic electrode Ti / Al / Mo / Au, before and after the current test The contact resistance at 3.8 × 10 ⁻⁶ Ωcm ² and 4.0 × 10 ⁻⁵ Ωcm ² , respectively, was found to increase 10 times.

  From the above experiments, the ohmic electrode according to the present invention has an extremely low contact resistance equivalent to that obtained with a conventional Ti / Al based ohmic electrode, and the conventional Ti / Al based ohmic electrode under a high temperature energization environment. It was found to be an excellent ohmic electrode with much higher stability.

In this example, the ohmic electrode according to the present invention was manufactured by heat-treating a multilayer structure of Ti / Mg / Mo / Au, but the film configuration, film thickness, and manufacturing method are not limited to those described in this example. Absent. For example, the metal in the first region formed in contact with the semiconductor surface may be Ta, Nb, Cr, V, Sn, In, Zr, Si, etc. in addition to Ti, and an alloy of these metals and Mg should be used. Is also possible. In addition, the electrode of the third region covering Ti / Mg is not limited to Mo / Au. For example, Au single-layer structure, two-layer structure such as Pt / Au, Ni / Au, Ti / Au, Nb / Au, Mo It is also possible to use a multilayer structure such as / Pt / Au, or an alloy thereof, both of which deteriorate the surface morphology of the n-type ohmic electrode and the edge of the electrode by heat treatment at a temperature higher than the melting point of Mg (650 ° C.) As a result, it is possible to form a chemically stable n-type ohmic electrode that is less prone to oxidation and corrosion of the electrode. The material of the second region may be Mg alone, but Mg ₃ Au is preferably used. In addition, although the formation method of each area | region of an electrode is not specifically limited, Although the photolithographic method, a vacuum evaporation method, a lift-off method, etc. are used and the heat processing method for alloying is not specifically limited, RTA method etc. are used. .

  In this embodiment, an example in which the n-type ohmic electrode according to the present invention is applied to a Schottky gate field effect transistor has been shown. However, according to the present invention, which has low contact resistance and high reliability with respect to an n-type nitride semiconductor. Considering the effect obtained, it is clear that the application range is not limited to this, and the present invention can be applied to a device that requires an n-type ohmic contact with a nitride-based semiconductor. Applications other than field effect transistors include, for example, light emitting diodes (LEDs), laser diodes (LD), pn junction diodes, Schottky diodes, resistance elements, MIS gate type field effect transistors, MOS gate type field effect transistors, hetero Examples thereof include a junction bipolar transistor (HBT).

(Second embodiment)
In the second embodiment, the n-type ohmic electrode according to the present invention is applied to a laser diode (LD). As shown in FIG. 7, this semiconductor laser has an Si-doped n-type GaN layer 702 (Si concentration 4 × 10 ¹⁷ cm ⁻³ , thickness 1 μm) on an n-type GaN substrate 701, Si-doped n-type Al _0.1. N-type cladding layer 703 made of Ga _0.9 N (Si concentration 4 × 10 ¹⁷ cm ⁻³ , thickness 2 μm), Si-doped n-type GaN (Si concentration 4 × 10 ¹⁷ cm ⁻³ , thickness 0.1 μm) N-type optical confinement layer 704, In _0.15 Ga _0.85 N (thickness 3 nm) well layer and Si-doped In _0.01 Ga _0.99 N (Si concentration 1 × 10 ¹⁸ cm ⁻³ , thickness 4 nm) three-period multiple quantum well (MQW) layer 705 made of a barrier layer, cap layer 706 made of Mg-doped p-type Al _0.2 Ga _0.8 N, Mg-doped p-type GaN (Mg concentration 2 × 10 ¹⁹ cm ^{− 3.} Thickness 0 .1 μm), a p-type GaN guide layer 707 is laminated. On top of this, a current confinement layer 708, a p-type cladding layer 709 made of Mg-doped p-type Al _0.1 Ga _0.9 N (Mg concentration 1 × 10 ¹⁹ cm ⁻³ , thickness 0.5 μm), Mg-doped A contact layer 710 made of p-type GaN (Mg concentration 1 × 10 ²⁰ cm ⁻³ , thickness 0.02 μm) is laminated. A p-type ohmic electrode 711 and an n-type ohmic electrode 712 of the present invention are provided at the upper and lower portions of this laminated structure, respectively.

  Here, in order to compare the n-type ohmic electrode according to the present invention with the conventional Ti / Al based ohmic electrode, the n-type ohmic electrode 712 is Ti / Mg (film thickness 5/23 nm) according to the present invention, and the conventional one. Ti / Al (film thickness 5/20 nm) was prepared. In any electrode, the n-type ohmic electrode 712 was formed by performing a heat treatment at 650 ° C. for 30 seconds after forming the metal two-layer structure by a vacuum deposition method. By this heat treatment, the n-type ohmic electrode 712 is alloyed. Ni / Au (film thickness 10/10 nm) was used for the p-type ohmic electrode 711. The sample after electrode formation was cleaved in the direction perpendicular to the electrode stripes to form an LD chip.

  An LD chip using Ti / Mg and Ti / Al as an n-type ohmic electrode was fused (mounted) to a heat sink at 300 ° C. using AuSn solder, and the emission characteristics were confirmed. In the case of Ti / Mg, the voltage is 4.3 ± 0.1 V, and in the case of Ti / Al, the voltage is 4.9 ± 0.4 V. By using the n-type ohmic electrode according to the present invention, the threshold voltage is reduced and the threshold value is increased. The variation in voltage could also be reduced. As a result of further detailed analysis, in the case of Ti / Al, an Al—Au reaction occurs between the AuSn solder material and the Ti / Al ohmic electrode at the time of fusion at 300 ° C., and the reaction part has a high resistance region. Moreover, it was found that the resistance of this part varied widely. On the other hand, in the case of Ti / Mg, it was found that there was no high resistance region, and as a result, it was possible to reduce variation in threshold voltage as well as variation.

  From the above experiment, when the n-type ohmic electrode according to the present invention is used, even when the Au and n-type ohmic electrode are connected, such as fusion (mounting) using AuSn or wire bonding using Au, There are no problems such as an increase in resistance as seen in conventional Ti / Al-based n-type ohmic electrodes, and device characteristics related to ohmic contact resistance (for example, reduction of threshold voltage of laser diode) and reproducibility are improved. I understood that I could plan.

  In this example, the ohmic electrode according to the present invention was manufactured by heat-treating a two-layer structure of Ti / Mg, but the film configuration, film thickness, and manufacturing method are not limited to those described in this example. For example, the metal in the first region formed in contact with the semiconductor surface may be Ta, Nb, Cr, V, Sn, In, Zr, Si, etc. in addition to Ti, and an alloy of these metals and Mg should be used. Is also possible. Further, Ti / Mg may be covered with an electrode of the third region containing Au, for example, Au single layer structure, double layer structure such as Pt / Au, Ni / Au, Ti / Au, Nb / Au, Mo It is also possible to use a multilayer structure such as / Pt / Au, or an alloy thereof, both of which prevent deterioration of the surface morphology of the n-type ohmic electrode due to heat treatment at a temperature higher than the melting point of Mg (650 ° C.). In addition, an effect that it is possible to form a chemically stable n-type ohmic electrode in which oxidation and corrosion of the electrode hardly occur is obtained.

  Examples of utilization of the present invention include semiconductor devices using nitride-based semiconductor materials, such as mobile phones, satellite communications, microwave transistors constituting wireless communication systems such as WLAN, large displays and blue / ultraviolet used for white illumination. Light emitting diodes, blue laser diodes necessary for recording / reproducing next-generation optical disks, and the like can be mentioned.

It is a phase diagram of the alloy of aluminum (Al) and gold (Au). It is a phase diagram of an alloy of magnesium (Mg) and gold (Au). It is sectional drawing explaining the field effect transistor by 1st embodiment of this invention. It is a figure which shows the relationship between the contact resistance of an n-type ohmic electrode and heat processing temperature in connection with 1st embodiment of this invention. It is a figure which shows the current-voltage characteristic before and behind a high temperature energization test at the time of applying the conventional n-type ohmic electrode to a field effect transistor. It is a figure which shows the current-voltage characteristic before and behind a high temperature energization test at the time of applying the n-type ohmic electrode of this invention to a field effect transistor. It is sectional drawing explaining the laser diode by 2nd embodiment of this invention.

Explanation of symbols

301 Substrate 302 AlN buffer layer 303 GaN channel layer 304 AlGaN electron supply layer 305 Source electrode (present invention)
306 Drain electrode (present invention)
307 Gate electrode 701 n-type GaN substrate 702 Si-doped n-type GaN layer 703 n-type cladding layer 704 n-type optical confinement layer 705 multiple quantum well (MQW) layer 706 cap layer 707 p-type GaN guide layer 708 current confinement layer 709 p-type Clad layer 710 Contact layer 711 p-type ohmic electrode 712 n-type ohmic electrode (present invention)

Claims (5)

An ohmic electrode formed on the surface of an n-type or non-doped nitride semiconductor, wherein a first region in contact with the nitride semiconductor surface is made of Ti, Ta, Nb, Cr, V, Sn, In, Zr, Si Among them, at least one metal or more is included, Mg is included in the second region formed thereon, and third region including Au is further formed on the second region including Mg. Is provided,
The n-type nitride semiconductor electrode, wherein none of the first to third regions contains Al .   2. The n-type nitride semiconductor electrode according to claim 1, wherein Mg is contained in the first region in contact with the nitride-based semiconductor surface in addition to the configuration. 3. The n-type nitride semiconductor electrode according to claim 1, wherein at least the first region and the second region are alloyed by heat treatment . A method for forming an ohmic electrode formed on an n-type or non-doped nitride semiconductor surface,
Forming a first layer containing at least one metal of Ti, Ta, Nb, Cr, V, Sn, In, Zr, and Si at a position in contact with the nitride-based semiconductor surface;
Forming a second layer containing Mg formed on the first layer;
Forming a third layer containing Au on the second layer containing Mg;
An ohmic electrode is formed by heat-treating the first layer, the second layer, and the third layer,
In addition, Al is not included in any of the first to third layers.
A method for forming an n-type nitride semiconductor electrode. 5. The method of forming an n-type nitride semiconductor electrode according to claim 4, wherein Mg is contained in the first layer in contact with the nitride-based semiconductor surface in addition to the configuration .

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