CN1332454C - Method for making a semiconductor light emitting element - Google Patents

Abstract

The invention provides a method for manufacturing a semiconductor light-emitting element. The method comprises forming at least one semiconductor laminated structure on a substrate surface, wherein the semiconductor laminated structure comprises a first conductive type semiconductor layer, a light emitting layer and a second conductive type semiconductor layer sequentially arranged on the substrate surface; then, an electrode contact layer containing indium element is formed on the surface of the semiconductor laminated structure, microwave treatment is carried out to activate the semiconductor laminated structure, and finally, a transparent conductive layer is formed on the surface of the electrode contact layer.

Description

Method for making a semiconductor light emitting element

technical field

The invention relates to a method for manufacturing a semiconductor light emitting element, especially a method for manufacturing an ohmic electrode of a semiconductor light emitting element.

Background technique

The application of III-V semiconductor materials, including compound semiconductor materials such as gallium nitride series (GaN series) and gallium arsenide (GaAs series) series, has become the research focus of light-emitting component manufacturing. These light-emitting components generally include an N-type conductive type III-V compound semiconductor layer and a P-type conductive type III-V compound semiconductor layer stacked on a substrate. In addition, a P-type contact electrode is provided above the P-type semiconductor layer to cooperate with the N-type contact electrode on the N-type semiconductor layer or on the back of the conductive material substrate to provide current to make the component emit light.

Generally speaking, the P-type contact electrode must cover the entire surface of the P-type semiconductor layer to provide uniform current to the P-type semiconductor layer so that the light-emitting component can generate uniform light. However, the light transmittance of the metal material used to make the contact electrode is not high, and if it completely covers the surface of the light-emitting component, it will definitely have a negative impact on the luminous efficiency of the light-emitting component. In order to take into account both luminous uniformity and luminous efficiency, the current improvement method is to cover a transparent conductive layer on the P-type semiconductor layer, and then arrange the P-type contact electrode on the transparent conductive layer to form an ohmic electrode.

Since the surface of the P-type semiconductor layer has many defects, the contact resistance between it and the transparent conductive layer increases, and it is difficult to form a good ohmic electrode. Existing technologies use methods such as metalorganic vapor phase epitaxy (MOVPE), molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (hybrid vapor phase epitzxy, HVPE) to fabricate these semiconductors. When layering, it must go through a high-temperature epitaxial growth process of about 900-1000 ° C, and at the same time add gas containing appropriate dopants to form a III-V compound semiconductor layer of N-type or P-type conductivity on the substrate.

In the above manufacturing process, the most common problem encountered is that the P-type semiconductor layer with sufficiently low resistance cannot be formed. The possible reason is that in the process of epitaxial growth, the occasional hydrogen incorporation (hydrogen incorporation) leads to acceptor passivation (acceptor passivation), which makes the hole carrier concentration insufficient, and even produces a semi-conductor with an impedance as high as 108Ω. Insulating material, also known as I-type semiconductor layer. In order to remove the hydrogen passivation phenomenon in the P-type semiconductor layer, so that the I-type semiconductor layer with high impedance can be converted into a P-type semiconductor layer, it has been proposed in the prior art that thermal annealing, electron beam irradiation or ultraviolet light irradiation can be used. technology to activate P-type semiconductor materials.

Because in order to form a good ohmic electrode, the P-type semiconductor conductive layer must have a high carrier concentration or a low work function, so it is generally not easy to achieve a P-type semiconductor conductive layer that can make a good ohmic electrode. Taking gallium nitride series light-emitting components as an example, the carrier concentration of the P-type semiconductor layer is difficult to reach above 5e18/cm3, while the P-type indium gallium nitride (InGaN) can easily achieve high carrier concentration and low work function However, in the activation process (such as thermal annealing) of the P-type semiconductor layer, its composition structure is easily destroyed due to high temperature, so that the P-type InGaN layer becomes a high-resistance layer.

In addition, in order to make a good ohmic electrode, in addition to the condition that the P-type semiconductor conductive layer must have a high concentration of carriers, the transparent conductive layer is also an important part. Taking ITO as an example, although in theory ITO can be used as a transparent conductive layer of III-N semiconductor, but in the literature or other published reports, such as Semiconductor Science and Technology, vol.18 (4), 2003, L21-L23 (1 ); Solid-State Electronics, vol.47(5), 2003, 849-853; Materials Science and Engineering B Vol.106(1), 2004, 69-72; Solid-State Electronics, vol.47(9), 2003, 1565-1568; Photonics Technology Letters, IEEE, Vol.15(5), 2003, 646-648, etc. It is stated in the literature that only ITO is used as the ohmic electrode of the P-GaN layer, although it has more than 95% light transmission rate, but cannot form a good ohmic electrode, all present too high component forward voltage. Therefore, Ni or Ni/Au is added between ITO and P-GaN to form a better ohmic electrode and reduce the forward voltage of the component, but Ni or Ni/Au has poor light transmission, so Ni/ITO or Ni/Au Au/ITO will degrade the luminous efficiency of the light-emitting component.

Contents of the invention

The object of the present invention is to provide a method for manufacturing a semiconductor light-emitting element, which can effectively increase the carrier concentration of the P-type semiconductor layer, and reduce its contact resistance with the transparent electrode, so as to form a good ohmic electrode.

In order to achieve the above object, the main technical solution adopted by the present invention is: the method includes forming at least one semiconductor stacked structure on the surface of a substrate, and the semiconductor stacked structure includes a first conductive type semiconductor layer, a light emitting layer and a second Conductive semiconductor layers are sequentially arranged on the surface of the substrate. Then an electrode contact layer containing indium element is formed on the surface of the semiconductor stack structure, and a microwave treatment is performed to activate the semiconductor stack structure, and finally a transparent conductive layer is formed on the surface of the electrode contact layer. The aforementioned microwave process is an ultra-low temperature process, so the present invention can also utilize microwaves to activate the semiconductor layer after forming the transparent conductive layer without affecting the quality of the transparent conductive layer.

Since the present invention arranges the electrode contact layer containing indium element in the semiconductor light-emitting element to increase the carrier concentration, and utilizes low-temperature microwave treatment to activate the semiconductor laminated structure, it can avoid the indium element being scattered or semiconducting due to high temperature activation. Impedance increase caused by quality deterioration and other problems can be obtained, and then a good ohmic electrode can be obtained.

Description of drawings

Below in conjunction with accompanying drawing and specific embodiment the utility model is described in further detail.

1 to 4 are method schematic diagrams of the first embodiment of the present invention;

5 to 7 are schematic diagrams of the method according to the second embodiment of the present invention.

Detailed ways

1 to 4 are schematic diagrams of a method for manufacturing a semiconductor light emitting device according to a first embodiment of the present invention. The semiconductor light emitting device of the present invention includes a light emitting diode, a laser diode, a photodetector, a solar cell, and the like. As shown in Figure 1, the present invention first provides a substrate 12 when making a semiconductor light-emitting element 10, such as a sapphire insulating substrate that can directly provide epitaxial growth, and then forms a first conductive type semiconductor layer 14 and a light-emitting layer on the surface of the substrate 12. 16 and a semiconductor layer 18 of the second conductivity type to form a semiconductor stack structure, and an electrode contact layer 20 containing indium elements of the first conductivity type or the second conductivity type is formed on the surface of the semiconductor stack structure. Since the electrode contact layer 20 containing indium element can provide a narrow material energy gap relative to the semiconductor layers 14, 18 below it, carriers can be gathered in the electrode contact layer 20 containing indium element to achieve good performance. High carrier concentration required for ohmic electrodes.

In a preferred embodiment of the present invention, the first conductivity type semiconductor layer 14 is an N-type doped compound semiconductor layer, such as an N-type silicon-doped gallium nitride layer; the light-emitting layer 16 is InGaN/GaN ( InGaN/GaN) multiple quantum well structure; the second conductivity type semiconductor layer 18 is a P-type doped compound semiconductor layer, such as a P-type magnesium-doped gallium nitride layer; The preferred thickness of the N-type or P-type InGaN layer larger than 500 angstroms (A) is about 20 angstroms. However, the present invention is not limited thereto, and other dopants and semiconductor materials applicable to semiconductor light-emitting elements are applicable to the present invention. In addition, another buffer layer, such as a gallium nitride layer, may be formed between the semiconductor stacked structure and the substrate 12 to prevent the surface lattice structure of the semiconductor layers 14 and 18 from being damaged during the high temperature process of epitaxial growth.

After that, as shown in FIG. 2 , a microwave treatment is performed on the semiconductor light emitting device 10 to activate the P-type doped layer, including the semiconductor layer 18 (and the electrode contact layer 20 ). Microwave treatment is a low-temperature treatment, and the operating temperature should be lower than 400° C. to avoid the increase of impedance caused by indium element scattering or deterioration of semiconductor quality. In order to achieve the purpose of mass production, the present invention can also carry out a preheating treatment before microwave treatment, preheating the substrate 12 to a predetermined temperature range, so that its temperature is higher than room temperature but lower than 400 ° C, to prevent P-type doping The impurity layer causes chip cracking during subsequent microwave processing.

As shown in Figures 3 and 4, a transparent conductive layer 22 is then formed on the surface of the electrode contact layer 20, and an etching process is performed to remove part of the transparent conductive layer 22, the electrode contact layer 20, the semiconductor layer 18, the light emitting layer 16 until the semiconductor layer 14, to form a contact electrode 24 on the surface of the semiconductor layer 14, and to form a contact electrode 25 on the surface of the transparent conductive layer 22. The transparent conductive layer 22 can be selected from the group consisting of metal, metal oxide and metal nitride, including nickel, gold, silver, chromium, platinum, indium zinc oxide (IZO), indium oxide, zinc oxide (ZnO), oxide Indium tin oxide (ITO), tin oxide, antimony tin oxide (ATO), antimony oxide, antimony zinc oxide (AZO), cadmium tin oxide (CTO), cadmium oxide, titanium nitride (TiN) , Tungsten Nitride (WN), Titanium Tungsten Nitride (TiWN), etc. In a preferred embodiment of the present invention, the contact electrode 24 can be formed of metals such as titanium/aluminum, and is used as an N-type contact electrode of the semiconductor light emitting element 10, and the contact electrode 25 can be made of nickel/gold, chromium/gold or platinum/gold, etc. Formed from metal, it is used as a P-type contact electrode of the semiconductor light emitting element 10 . In addition, when the substrate 12 is formed of an N-type semiconductor material, the N-type contact electrode can also be directly formed on the back surface of the substrate 12, so as to omit the transparent conductive layer 22, the electrode contact layer 20, the semiconductor layer 18, and the light-emitting layer 16 in the aforementioned etched portion. and other steps.

Compared with the method of high temperature activation of P-type semiconductor layer such as thermal annealing, the present invention uses ultra-low temperature microwave process to activate P-type semiconductor layer, which can not only shorten the activation time, effectively reduce the impedance of P-type semiconductor layer, but also avoid the indium-containing element The electrode contact layer is damaged by high temperature during the activation process, so the semiconductor light-emitting element can have a high carrier concentration to form a good ohmic electrode.

In order to prevent the quality of the transparent conductive layer from being affected by the high-temperature annealing process, the existing method is to activate the P-type semiconductor material layer at high temperature before manufacturing the transparent conductive layer. However, since the microwave process is an ultra-low temperature process with an operating temperature lower than 400° C., the present invention can also use microwaves to activate the P-type semiconductor layer after forming the transparent conductive layer without affecting the quality of the transparent conductive layer.

5 to 7 are schematic diagrams of a method for manufacturing a semiconductor light emitting device according to a second embodiment of the present invention. The semiconductor light emitting device of the present invention includes a light emitting diode, a laser diode, a photodetector, a solar cell, and the like. As shown in Figure 5, the present invention first provides a substrate 32 when making the semiconductor light-emitting element 30, such as a sapphire insulating substrate that can directly provide epitaxial growth, and then forms a first conductive type semiconductor layer 34 and a light-emitting layer on the surface of the substrate 32. 36 and the semiconductor layer 38 of the second conductivity type to form a semiconductor stack structure, and an electrode contact layer 40 containing indium elements of the first conductivity type or the second conductivity type is formed on the surface of the semiconductor stack structure. Since the electrode contact layer 40 containing indium element can provide a narrow material energy gap relative to the semiconductor layers 34, 38 below it, carriers can be gathered in the electrode contact layer 40 containing indium element to achieve good High carrier concentration required for ohmic electrodes.

In a preferred embodiment of the present invention, the first conductivity type semiconductor layer 34 is an N-type doped compound semiconductor layer, such as an N-type silicon-doped gallium nitride layer; the light-emitting layer 36 is InGaN/GaN ( InGaN/GaN) multiple quantum well structure; the second conductivity type semiconductor layer 38 is a P-type doped compound semiconductor layer, such as a P-type magnesium-doped gallium nitride layer; The preferred thickness of the N-type or P-type InGaN layer larger than 500 angstroms (A) is about 20 angstroms. However, the present invention is not limited thereto, and other dopants and semiconductor materials applicable to semiconductor light-emitting elements are applicable to the present invention. In addition, another buffer layer, such as a gallium nitride layer, may be formed between the semiconductor stacked structure and the substrate 32 to prevent the surface lattice structure of the semiconductor layers 34 - 38 from being damaged during the high temperature process of epitaxial growth.

After that, as shown in FIG. 6, a transparent conductive layer 42 is formed on the surface of the electrode contact layer 40, and a microwave treatment is performed on the semiconductor light-emitting element 30 to activate the P-type doped layer, including the semiconductor layer 38 (and the electrode contact layer 40) . The transparent conductive layer 42 can be selected from the group consisting of metal, metal oxide and metal nitride, including nickel, gold, silver, chromium, platinum, indium zinc oxide (IZO), indium oxide, zinc oxide (ZnO), oxide Indium tin oxide (ITO), tin oxide, antimony tin oxide (ATO), antimony oxide, antimony zinc oxide (AZO), cadmium tin oxide (CTO), cadmium oxide, titanium nitride (TiN) , Tungsten Nitride (WN), Titanium Tungsten Nitride (TiWN), etc. Microwave treatment is a low-temperature treatment, and the operating temperature should be lower than 400° C. to avoid the increase of impedance caused by indium element scattering or deterioration of semiconductor quality. In order to achieve the purpose of mass production, the present invention can also carry out a preheating treatment before microwave treatment, preheating the substrate 32 to a predetermined temperature range, making its temperature higher than room temperature but lower than 400 ° C, to prevent P-type doping The cracking of the heterolayer during the subsequent microwave treatment.

As shown in FIG. 7, an etching process is then performed to remove part of the transparent conductive layer 42, the electrode contact layer 40, the semiconductor layer 38, the light emitting layer 36 until the surface of the semiconductor layer 34, so as to form a contact electrode 44 on the surface of the semiconductor layer 34. A contact electrode 45 is formed on the surface of the transparent conductive layer 42 . In a preferred embodiment of the present invention, the contact electrode 44 can be formed of metals such as titanium/aluminum, and is used as an N-type contact electrode of the semiconductor light emitting element 30, and the contact electrode 45 can be made of nickel/gold, chromium/gold or platinum/gold, etc. Formed from metal, it is used as a P-type contact electrode of the semiconductor light emitting element 30 . In addition, when the substrate 32 is formed of an N-type semiconductor material, the N-type contact electrode can also be directly formed on the back surface of the substrate 32, so as to omit the transparent conductive layer 42, the electrode contact layer 40, the semiconductor layer 38, and the light-emitting layer 36 in the aforementioned etched portion. and other steps.

Claims (8)

1, a kind of method of making semiconductor light emitting component, this method includes the following step:

(1) provides a substrate;

(2) form semiconductor layered structure at least in described substrate surface, and this semiconductor lamination structure includes one first conductive type semiconductor layer, a luminescent layer and one second conductive type semiconductor layer and is located at this substrate surface in regular turn;

(3) form a contact electrode layer that contains phosphide element in described semiconductor lamination body structure surface;

(4) form a transparency conducting layer in described contact electrode layer surface;

(5) after forming described transparency conducting layer, carry out a Microwave Treatment, to activate described semiconductor lamination structure.

2, according to the method for the described making semiconductor light emitting component of claim 1, it is characterized in that: described first conductive type is the N type, and described second conductive type is the P type.

3, according to the method for the described making semiconductor light emitting component of claim 1, it is characterized in that: described Microwave Treatment is the p type semiconductor layer that is used for activating in the described semiconductor lamination structure.

4, according to the method for the described making semiconductor light emitting component of claim 1, it is characterized in that: described contact electrode layer is formed by the P type semiconductor material, and utilizes described Microwave Treatment to be activated.

5, according to the method for the described making semiconductor light emitting component of claim 1, it is characterized in that: described transparency conducting layer is selected from the group that metal, metal oxide and metal nitride are formed.

6, according to the method for the described making semiconductor light emitting component of claim 1, it is characterized in that: the operating temperature of described Microwave Treatment is less than 400 ℃.

7, according to the method for the described making semiconductor light emitting component of claim 1, it is characterized in that: the thickness of described contact electrode layer is not more than 500 dusts.

8, according to the method for the described making semiconductor light emitting component of claim 1, it is characterized in that: described semiconductor light-emitting elements comprises light-emitting diode, laser diode, photodetector or solar cell.

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