CN105390541A - HEMT epitaxial structure and preparation method thereof - Google Patents

Abstract

<b>The present invention provides a </b><b>HEMT</b><b> epitaxial structure and its preparation method, </b><b>HEMT</b><b> epitaxial structure, including sequential Stacked substrate, buffer layer, non-doped or doped high-resistance layer, non-doped high-mobility layer and </b><b>GaN/AlN</b><b> superlattice gate layer, The period of the </b><b>GaN/AlN</b><b> superlattice gate layer is </b><b>4~15</b><b>. The total thickness of the </b><b>GaN/AlN</b><b> superlattice gate layer is </b><b>6~30nm</b><b>, and</b><b> The thickness ratio of b><b>AlN</b><b> and </b><b>GaN</b><b>is</b><b>1:1~1:9</b><b>. Through the unique layer-by-layer stress release characteristics of the superlattice structure, a large number of surface defects caused by excessive stress at the </b><b>AlGaN/GaN</b><b> interface can be effectively reduced. </b>

Description

HEMTs Epitaxial structure and its preparation method

technical field

The present invention relates to a HEMTs Epitaxial structures and methods for their preparation.

Background technique

In the prior art, HEMTs Epitaxial wafers are usually AlGaN/GaN or AlGaN/AlN/GaN as the gate layer, and this standard AlGaN/GaN or AlGaN/AlN/GaN HEMTs structure, due to AlGaN/GaN If the stress at the interface is too large, more surface defects will be generated, which will increase the leakage probability of the device.

Contents of the invention

For the problems referred to above, the purpose of the present invention is to provide a kind of HEMTs An epitaxial structure and a preparation method thereof, which effectively reduce surface defects.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A sort of HEMTs Epitaxial structure, including sequentially stacked substrate, buffer layer, non-doped or doped high resistance layer, non-doped high mobility layer and GaN/AlN superlattice gate layer, the GaN/AlN The period of the superlattice gate layer is 4~15 .

Preferably, the GaN/AlN The total thickness of the superlattice gate layer is 6~30nm ,and AlN and GaN The thickness ratio is 1:1~1:9 .

Preferably, the buffer layer is GaN layer, AlN layer, AlGaN layer, InGaN layer or AlInGaN layer.

Preferably, the thickness of the buffer layer is 10~100nm .

Preferably, the thickness of the non-doped or doped high resistance layer is 0.1~3 mu m , resistivity ρ >1E8 Ω ∙m .

More preferably, the doped high resistance layer doped with iron or chromium is laminated between the buffer layer and the non-doped high resistance layer. GaN layer.

More preferably, the layer stacked between the buffer layer and the non-doped high-resistance layer is a non-doped high-resistance GaN layer.

Preferably, the non-doped high mobility layer has a thickness of 50~200nm of GaN layer.

a kind of above HEMTs A method for preparing an epitaxial structure, comprising the steps of:

A place the substrate in 1050~1250 ℃ H2 High temperature purification under atmosphere 5~10min ;

B exist H2 step A The cleaned substrate was cooled to 500~600 After ℃, a buffer layer is grown on the substrate;

C The substrate on which the buffer layer was grown was heated to 1000~1200 °C, grow a non-doped or doped high-resistance layer on the buffer layer;

D. Keeping the temperature constant, grow a non-doped high-mobility layer on the non-doped or doped high-resistance layer;

E. cool down to 950~1100 °C, grown on the non-doped high-mobility layer GaN/AlN superlattice gate layer.

Preferably, the buffer layer, undoped or doped high resistance layer, undoped high mobility layer and GaN/AlN The superlattice gate layer passes through MOCVD Craft grows.

The present invention adopts the above technical scheme, and has the following advantages compared with the prior art: through the characteristic of layer-by-layer release of the unique stress of the superlattice structure, it can effectively reduce AlGaN/GaN A large number of surface defects caused by excessive stress at the interface.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work, wherein:

picture 1 for the present invention HEMTs Schematic diagram of the epitaxial structure;

picture 2 used in existing technology AlGaN/AlN/GaN gate layer HEMTs The surface of the epitaxial structure AFM picture;

picture 3 for the present invention HEMTs epitaxy AFM picture.

In the above drawings, 1 , Substrate; 2 ,The buffer layer; 3 , doped high resistance layer; 4 , non-doped high mobility layer; 5 , GaN/AlN superlattice gate layer.

detailed description

The preferred embodiments of the present invention are described in detail below, so that the advantages and features of the present invention can be more easily understood by those skilled in the art.

picture 1 Shown is a kind of the present invention HEMTs epitaxial structure. Combined graph 1 As shown, the HEMTs The epitaxial structure includes substrates stacked sequentially from bottom to top 1 ,The buffer layer 2 , non-doped or doped high-resistance layer 3 , non-doped high mobility layer 4 and GaN/AlN superlattice gate layer 5 .

Substrate 1 Aluminum oxide ( Al ₂ O ₃ ) substrate.

superlattice gate layer 5 The cycle is 4~15 . GaN/AlN superlattice gate layer 5 The total thickness of 6~30nm ,and AlN and GaN The thickness ratio is 1:1~1:9 . compared to standard AlGaN/GaN or AlGaN/AlN/GaN HEMTs structure, through the unique layer-by-layer stress release characteristics of the superlattice structure, it can effectively reduce the stress AlGaN/GaN A large number of surface defects caused by excessive stress at the interface can improve the leakage characteristics of the device.

The buffer layer 2 for GaN layer, AlN layer, AlGaN layer, InGaN layer or AlInGaN layer. In this example, the buffer layer 2 for GaN layer. The buffer layer 2 The thickness is 10~100nm .

Undoped or doped high resistance layer 3 The thickness is 0.1~3 mu m , resistivity ρ >1E8 Ω ∙ m . In this embodiment, laminated on the buffer layer 2 and the non-doped high resistance layer 3 between doped iron or chromium doped high resistance GaN layer. layered on the buffer layer 2 and the non-doped high resistance layer 3 between can also be non-doped high-resistance GaN layer.

Undoped high mobility layer 4 is the thickness of 50~200nm of GaN layer.

a kind of above HEMTs A method for preparing an epitaxial structure, comprising the steps of:

A , provide the substrate 1 , the substrate 1 exist 1050~1250 ℃ H2 High temperature baking under atmosphere 5~10min Substrate 1 purify;

B exist H2 step A Purified substrate 1 cool down to 500~600 ℃ after the substrate 1 upper growth buffer 2 ;

C will grow with a buffer layer 2 the substrate 1 heat up to 1000~1200 ℃, in the buffer layer 2 Non-doped or doped high-resistance layer grown on 3 ;

D. Keep the growth temperature constant, in the non-doped or doped high resistance layer 3 undoped high mobility layer 4 ;

E. Substrate 1 cool down to 950~1100 ℃, in the non-doped high mobility layer 4 grow up GaN/AlN superlattice gate layer 5 .

step C , D. , E. for growth HEMTs structural layer of the epitaxial structure, the buffer layer 2 , non-doped or doped high-resistance layer 3 , non-doped high mobility layer 4 and GaN/AlN superlattice gate layer 5 both pass MOCVD Craft grows. MOCVD The process is the metal organic compound chemical vapor deposition process ( Metal-organic Chemical Vapor Deposition ).

State-of-the-art standards by atomic force microscopy HEMTs epitaxial structure and the present invention HEMTs The surface of the epitaxial structure is probed, and the measured surface AFM See Fig. 2 , 3 . Combined graph 2 , 3 As shown, the present invention's HEMTs The surface defects of the epitaxial structure are higher than the standard in the prior art HEMTs The epitaxial structure is significantly reduced.

The above-mentioned embodiment is only to illustrate the technical concept and characteristics of the present invention. It is a preferred embodiment, and its purpose is to allow those familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot limit the present invention. scope of protection. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A HEMT epitaxial structure, characterized in that: comprise successively stacked substrates, buffer layers, non-doped or doped high-resistance layers, non-doped high-mobility layers and GaN/AlN superlattice gate layers, The period of the GaN/AlN superlattice gate layer is 4-15. 2. HEMT epitaxial structure according to claim 1, is characterized in that: the total thickness of described GaN/AlN superlattice gate layer is 6～30nm, and the thickness ratio of AlN and GaN is 1:1～1: 9. 3. The HEMT epitaxial structure according to claim 1, wherein the buffer layer is a GaN layer, an AlN layer, an AlGaN layer, an InGaN layer or an AlInGaN layer. 4. The HEMT epitaxial structure according to claim 1, characterized in that: the thickness of the buffer layer is 10-100 nm. 5. The HEMT epitaxial structure according to claim 1, characterized in that: the thickness of the non-doped or doped high-resistance layer is 0.1-3 μm, and the resistivity ρ>1E8Ω∙m. 6 . The HEMT epitaxial structure according to claim 5 , wherein the layer stacked between the buffer layer and the non-doped high-resistance layer is a doped high-resistance GaN layer doped with iron or chromium. 7 . The HEMT epitaxial structure according to claim 5 , wherein the layer stacked between the buffer layer and the non-doped high-resistance layer is a non-doped high-resistance GaN layer. 8 . The HEMT epitaxial structure according to claim 1 , wherein the non-doped high-mobility layer is a GaN layer with a thickness of 50-200 nm. 9. A method for preparing the HEMT epitaxial structure according to any one of claims 1-8, comprising the steps of: A. Purify the substrate at high temperature for 5-10 minutes under H2 atmosphere at 1050-1250°C; B cool down the substrate purified in step A to 500~600°C in H2 atmosphere, and then grow a buffer layer on the substrate; C. Raise the temperature of the substrate with the buffer layer to 1000~1200°C, and grow a non-doped or doped high-resistance layer on the buffer layer; D keeps the temperature constant, and grows a non-doped high-mobility layer on the non-doped or doped high-resistance layer; E is cooled to 950~1100°C, and a GaN/AlN superlattice gate layer is grown on the non-doped high mobility layer. 10. The preparation method according to claim 9, characterized in that: the buffer layer, the non-doped or doped high-resistance layer, the non-doped high-mobility layer and the GaN/AlN superlattice gate layer are processed by MOCVD Craft grows.