CN102054673B - Method for fabricating III-nitride semiconductor material pn (phosphorus nitride) junction - Google Patents

Abstract

A method for manufacturing a pn junction of a III-nitride semiconductor material, comprising the following steps: Step 1: growing a p-type GaN-based material on a substrate; Step 2: epitaxially non-doped GaN-based material on a p-type GaN-based material ; Step 3: growing a non-doped thin layer on the non-doped GaN-based material; Step 4: growing an n-type GaN-based material on the non-doped thin layer.

Description

Ⅲ-Nitride semiconductor material pn junction fabrication method

technical field

The invention relates to the technical field of semiconductor materials, in particular to a method for manufacturing a pn junction of a III-nitride semiconductor material.

Background technique

III-Nitride is the third-generation new semiconductor material after the first and second-generation semiconductor materials such as Si and GaAs. Among them, GaN has many advantages as a wide-bandgap semiconductor material, such as high saturation drift speed, large breakdown voltage, It has excellent carrier transport performance and can form AlGaN, InGaN ternary alloys and AlInGaN quaternary alloys, etc., and it is easy to make GaN-based pn junctions. In view of this, GaN-based materials and devices have been extensively and in-depth researched in recent years, and the growth of GaN-based materials by MOCVD technology has become increasingly mature; in terms of device research, GaN-based LEDs, LDs and other optoelectronic devices and GaN-based high mobility transistors (HEMTs) ) and other microelectronic devices have achieved remarkable results and considerable development. One of the difficulties in the growth of GaN-based device structure materials is the growth of high-performance GaN-based pn junctions (n-type layer on top of the p-type layer). The main reason for this difficulty is the presence of Mg memory in the growth of p-type GaN. effect. When growing p-type GaN-based materials by MOCVD technology, due to the presence of a large amount of H in the MOCVD growth environment, the acceptor dopant Mg in GaN is passivated by a large amount of H without generating holes, so that the concentration of free holes after activation treatment is higher than that of Mg The atomic doping concentration is 2-3 orders of magnitude lower. Therefore, in order to obtain a sufficient hole concentration, a large doping concentration is required, and since the organometallic compound of the p-type dopant Mg is dipentyl magnesium (Cp2Mg), this compound has a low saturated vapor pressure and strong surface adhesion, even if Turn off the organic source, there will be a lot of residues in the growth chamber and the surface of the material, so after the growth of the p-type layer, a magnesium-rich layer will be formed on the surface of the material, and a large number of Mg atoms will enter the n-type layer grown on it , causing the pn junction surface to be blurred and part of the n-type layer to be compensated, causing the pn junction to fail in severe cases. It is precisely because of this difficulty that the research on GaN-based devices with a pn junction (n-type layer above the p-type layer) structure lags behind and the development is slow, such as GaN-based bipolar transistors (BJTs and HBTs). In order to overcome this difficulty, the measures taken at present mainly include: after growing the p-type layer, use a gas that does not contain Mg atoms to purge and bake the growth chamber and lining for a long time to reduce residual Mg, see D.J.H.Lambert, D.E.Lin, R.D. Dupuis.Simulation of the electrical characteristics of AlGaN/GaNheterojunction bipolar transistors.Solid-State Electron.2000, 44:253; or use the secondary epitaxy method, that is, take it out of the growth chamber after growing the p-type layer, and put it in without using Mg Re-grow n-type layer in the source growth chamber or use MBE technology to epitaxial n-type layer, see Lee S.McCarthy, Ioulia P.Smorchkova, Huili Xing, et.al, GaNHBT: Toward an RF Device.IEEE Trans Electron Dev , 48:543, 2001. However, since the Mg atoms entering the n-type layer have a lot to do with the redistribution of Mg in the Mg-rich layer formed when growing the p-type layer, the method of purging the growth chamber for a long time or using the method of secondary epitaxy has a great effect on reducing the memory of Mg The effect is not obvious, and it causes the complexity of the growth process, which easily leads to the decline of the crystal quality of the secondary growth layer, and reduces the performance of the pn junction.

Contents of the invention

According to the problems raised above, the object of the present invention is to provide a method for fabricating a III-nitride semiconductor material pn junction, especially a method for fabricating a GaN-based pn junction that can reduce the Mg memory effect. Using this method to grow the GaN-based pn junction can control the surface Mg-rich layer caused by the memory effect of Mg in the p-type layer and reduce the concentration of Mg entering the n-type layer, increasing the p-type doping of the pn junction surface. Impurity steepness, thereby improving the performance of the pn junction.

The invention provides a method for manufacturing a pn junction of a III-nitride semiconductor material, comprising the following steps:

Step 1: growing a p-type GaN-based material on a substrate;

Step 2: epitaxial non-doped GaN-based material on the p-type GaN-based material;

Step 3: growing a non-doped thin layer on the non-doped GaN-based material;

Step 4: growing n-type GaN-based material on the non-doped thin layer.

Wherein when p-type GaN-based material is grown on the substrate, dipentyl magnesium is used as a p-type dopant source.

Among them, p-type GaN-based materials, non-doped GaN-based materials, non-doped thin layers, and n-type GaN-based materials are prepared by metal-organic chemical vapor deposition technology.

The growth temperature of the non-doped GaN-based material is in the range of 900°C-1050°C, and the thickness is 5-15nm.

The non-doped thin layer is a non-doped GaN-based material.

The growth temperature of the non-doped thin layer is in the range of 550°C-800°C, and the thickness is 3-10nm.

Wherein the non-doped thin layer is grown using triethylgallium or trimethylgallium as the metal-organic source of gallium.

The GaN-based material refers to III-nitride semiconductor materials such as GaN, AlGaN, AlN, InGaN, InN, and AlInGaN.

This growth method can reduce the memory effect of Mg during the growth of the GaN-based pn junction. Compared with the traditional continuous growth n-AlGaN/p-GaN structure, the results of secondary ion mass spectrometry show that in the AlGaN/GaN pn junction grown by this method The magnesium-rich layer in the p-type layer does not enter the n-type AlGaN layer in a large amount like the traditional method, but stops at the pn junction, and the background concentration delay of Mg in the n-type AlGaN decreases significantly, and the p-type doping The steepness of the interface is reduced from the usual 110nm/decade to 60nm/decade. Therefore, the use of this new growth method can reduce the memory effect of Mg, thereby increasing the interface doping steepness of the GaN-based pn junction and improving the performance of the pn junction.

Description of drawings

In order to further illustrate the specific technical content of the present invention, the following detailed description is as follows in conjunction with the embodiments and accompanying drawings, wherein:

Fig. 1 is a schematic diagram of the pn junction growth method of the present invention;

Fig. 2 is the SIMS (secondary ion mass spectrometry) collection of illustrative plates of the pn junction sample that the inventive method grows;

Fig. 3 is the SIMS spectrum of sample one;

Figure 4 is the SIMS spectrum of sample two.

Detailed ways

See also shown in Fig. 1, the present invention proposes a kind of fabrication method of III-nitride semiconductor material pn junction, comprises the following steps:

Step 1: growing p-type GaN-based material 10 on a substrate 100; when growing p-type GaN-based material 10 on substrate 100, dipentyl magnesium is used as a p-type dopant source;

Step 2: epitaxial non-doped GaN-based material 11 on the p-type GaN-based material 10; the growth temperature of the non-doped GaN-based material 11 is in the range of 900°C-1050°C, and the thickness is 5-15nm;

Step 3: growing a non-doped thin layer 12 on the non-doped GaN-based material 11; the non-doped thin layer 12 is a non-doped GaN-based material; the growth temperature of the non-doped thin layer 12 is 550°C In the range of -800°C, the thickness is 3-10nm; when growing the non-doped thin layer 12, triethylgallium or trimethylgallium is used as the metal-organic source of gallium;

Step 4: growing n-type GaN-based material 13 on the non-doped thin layer 12 .

The p-type GaN-based material 10, the non-doped GaN-based material 11, the non-doped thin layer 12, and the n-type GaN-based material 13 are prepared by metal-organic chemical vapor deposition technology.

We used MOCVD technology to grow npn-type AlGaN/GaN heterojunction bipolar transistors (HBTs) materials on a 2-inch sapphire substrate (0001), where the emitter junction of heterojunction bipolar transistors (HBTs) is a pn junction , when growing the emitter junction (a layer of n-type GaN-based material AlGaN grown on the p-type GaN), the growth method of the present invention is adopted, and the emitter junction is grown according to the growth sequence shown in Figure 1, that is, the substrate material 100 ( In this specific embodiment, the substrate material 100 refers to the GaN material in the collection region) on which the Mg-doped p-type GaN-based material 10 is grown, and the non-doped GaN-based material 11 is grown after the growth of the p-type GaN-based material 10. The growth conditions of the GaN-based material 11 are the same as the growth conditions of the Mg-doped p-type GaN-based material 10 except that the Cp ₂ Mg source is turned off, and other conditions (growth temperature, pressure, flow rate, etc.) It is about 10nm. After the growth of the non-doped GaN-based material 11 is completed, the temperature of the growth chamber is lowered, and an epitaxial non-doped layer 12 of about 8nm is grown at 550° C. region, and then grow n-type GaN-based material 13 (n-type GaN-based material 13 refers to n-type AlGaN material in this specific embodiment).

Figure 2 is the secondary ion mass spectrometry analysis results of Al in the n-type GaN-based material 13 (n-type AlGaN) and Mg in the p-type layer (GaN) in the emitter junction grown by this method. It can be seen from the figure that p The BB' area on the surface of the type base region is a magnesium-rich layer. Since the magnesium source is turned off to grow the non-doped GaN-based material 11, the magnesium-rich layer is located before the growth of the n-type GaN-based material 13 (position A in the figure indicates that AlGaN starts to grow), and the memory The tailing of the Mg secondary ion mass spectrum (change in doping concentration) caused by the effect can be used to evaluate the steepness of junction doping. In Figure 2, the change in junction doping concentration is about 60nm/decade.

In order to show the superiority of this growth method, we grew two samples (sample 1 and sample 2) by two methods different from the present invention, so as to compare with the samples grown by the method of our invention. The first growth method is (sample 1) when growing the emitter junction (grow a layer of n-type AlGaN on top of p-type GaN), after growing the Mg-doped p-type GaN-based material 10, and then using high temperature (about 1000°C) to grow Undoped GaN-based material 11 and n-type GaN-based material 13 (emitter region). The results of secondary ion mass spectrometry analysis of Al and Mg components in the emitter junction grown by this method are shown in Figure 3. It can be seen that the BB' magnesium-rich layer overlaps with the n-type GaN-based material 13 (n-type AlGaN), indicating that Mg The magnesium-rich layer caused by the memory effect appears in the emission region, which will cause severe compensation of the pn junction, and the doping concentration of the junction surface varies by about 90nm/decade. The second growth method (sample 2) is to grow the Mg-doped p-type GaN-based material 10, and then grow the non-doped GaN-based material 11. The growth condition of the non-doped GaN-based material 11 is to turn off the Cp ₂ Mg source, Other growth conditions are the same as those of the Mg-doped p-type GaN-based material 10, the growth time is about 2 minutes, and the thickness is about 10 nm; impurity layer 12, and then grow n-type GaN-based material 13 (n-type AlGaN). The results of secondary ion mass spectrometry analysis of Al and Mg components in the emitter junction grown by this method are shown in Figure 4. It can be seen that there is basically no overlap between the BB′ magnesium-rich layer and the AlGaN layer, indicating that the growth of the Mg-doped p-type layer Growing a layer of non-doped GaN-based material 11 after the GaN-based material 10 can effectively prevent pn junction compensation or even failure caused by the formation of a magnesium-rich layer in the n-type GaN-based material 13 (n-type AlGaN). In the low-temperature grown non-doped thin layer 12 used in the present invention, the tailing of the Mg element in the n-type GaN-based material 13 (n-type AlGaN) is still serious, and the doping concentration change of the pn junction surface is about 80nm/decade. The doping steepness of the pn junction grown by the above two methods is significantly worse than that of the pn junction grown by the method used in the present invention (the change of Mg doping concentration is about 60nm/decade).

Therefore, the method for growing the III-nitride semiconductor pn junction in the present invention can effectively reduce the memory effect of Mg at the pn junction interface.

Although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the claims.

Claims (7)

1. A method for making a III-nitride semiconductor material pn junction, comprising the steps of: Step 1: growing a p-type GaN-based material on a substrate; Step 2: epitaxial non-doped GaN-based material on the p-type GaN-based material; Step 3: growing a non-doped thin layer on the non-doped GaN-based material, the thickness of the non-doped thin layer is 3-10 nm; Step 4: growing an n-type GaN-based material on the non-doped thin layer; The temperature in which the non-doped thin layer is grown is lower than the temperature of the epitaxial non-doped GaN-based material. 2. The method for manufacturing a pn junction of III-nitride semiconductor material according to claim 1, wherein when growing a p-type GaN-based material on a substrate, dipentyl magnesium is used as a p-type dopant source. 3. the manufacture method of III-nitride semiconductor material pn junction according to claim 1, wherein prepare p-type GaN base material, non-doped GaN base material, non-doped thin layer, n-type GaN base material adopt It is a metal-organic chemical vapor deposition technique. 4. The method for fabricating a pn junction of III-nitride semiconductor material according to claim 1, wherein the growth temperature of the undoped GaN-based material is in the range of 900°C-1050°C, and the thickness is 5-15nm. 5. The method for fabricating a pn junction of III-nitride semiconductor material according to claim 1, wherein the non-doped thin layer is a non-doped GaN-based material. 6. The method for fabricating a pn junction of III-nitride semiconductor material according to claim 1 or 5, wherein the growth temperature of the non-doped thin layer is in the range of 550°C-800°C. 7. The method for fabricating a pn junction of III-nitride semiconductor material according to claim 1 or 5, wherein triethylgallium or trimethylgallium is used as the metal-organic source of gallium when growing the non-doped thin layer.

Images