GaN-based HEMT (High Electron Mobility Transistor) radio frequency device with gallium oxide back barrier structure
By introducing β-Ga2O3 as a back barrier layer and InAlN/GaN heterojunction structure, the problem of insufficient 2DEG confinement in GaN HEMT devices is solved, improving the DC and RF performance of the devices, and enhancing material quality and reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-08
- Publication Date
- 2026-04-07
AI Technical Summary
Traditional GaN HEMT devices suffer from insufficient 2DEG confinement due to the GaN buffer layer, severe buffer layer leakage, and limited improvement of the AlGaN back barrier, which may introduce parasitic channels.
β-Ga2O3 is used as the natural back barrier layer, combined with the InAlN/GaN heterojunction structure to form an ultrawide bandgap to enhance electronic confinement. Furthermore, the epitaxial stress and defects are reduced by lattice matching between the InAlN barrier layer and the GaN channel layer.
Significantly reduces leakage current, improves the DC and RF characteristics of devices, enhances material quality and reliability, increases electron mobility and transport efficiency, and improves the current output capability and RF performance of devices.
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Figure CN121815706A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a GaN-based HEMT radio frequency device with a gallium oxide back barrier structure and belongs to the technical field of semiconductor radio frequency power device manufacturing. BACKGROUND
[0002] Gallium nitride (GaN) high electron mobility transistors (HEMTs) have shown great application potential in radio frequency and power electronics due to their high frequency and high power characteristics. The excellent performance of GaN-based HEMT devices is mainly attributed to the high-concentration and high-mobility two-dimensional electron gas (2DEG) induced by strong polarization effect at the AlGaN / GaN or InAlN / GaN heterojunction interface.
[0003] In the traditional GaN HEMT epitaxial structure, a relatively thick intrinsic or weakly doped GaN buffer layer is usually grown directly on a substrate (such as sapphire, SiC or Si). In this traditional structure, the GaN buffer layer serves as both the foundation for material growth of the upper heterojunction structure and as an insulating layer. However, this single heterojunction structure with GaN as the buffer layer has an inherent defect: due to the limited conduction band offset of GaN material, its confinement ability for 2DEG in the channel is insufficient, resulting in a portion of high-energy electrons overflowing from the main channel and injecting into the underlying GaN buffer layer. This carrier overflow effect not only causes current leakage, reducing the transconductance and output resistance of the device, but also forms a parasitic conductive channel in the buffer layer under high electric field, severely deteriorating the breakdown voltage of the device.
[0004] To enhance the confinement of 2DEG and suppress buffer layer leakage, the industry generally adopts a solution of introducing an AlGaN back barrier layer, i.e. inserting an AlGaN layer with fixed Al composition between the GaN channel layer and the GaN buffer layer to form a double heterojunction structure. Although the AlGaN back barrier improves the electron confinement ability to some extent, the improvement is limited and new problems are introduced. First, the critical breakdown field of conventional AlGaN material is still not high enough, limiting the further improvement of the device's voltage withstand capability. Second, the interface between the AlGaN back barrier and the GaN buffer layer will induce a parasitic channel due to polarization discontinuity. In addition, there is a lattice mismatch between AlGaN and GaN, and introducing a high Al composition will increase the epitaxial stress and lattice defect density, negatively affecting the material quality and device reliability.
[0005] Therefore, exploring a new type of back barrier with strong electron confinement, high breakdown voltage and process compatibility has become the key to optimizing the radio frequency characteristics of GaN HEMT and improving its output power and efficiency. SUMMARY
[0006] In order to solve the problems of the traditional GaN-based HEMT device, such as the insufficient 2DEG constraint caused by the use of GaN buffer layer, the serious leakage of the buffer layer, and the limited improvement and possible introduction of parasitic channels caused by the adoption of AlGaN back barrier, the application provides a GaN-based HEMT radio frequency device with a gallium oxide back barrier structure (InAlN / GaN HEMT radio frequency device). The core of the device is to use the super-wide band gap characteristics of β-Ga2O3 as a natural back barrier layer to fundamentally optimize the electrical performance of the device.
[0007] Technical content: A GaN-based HEMT radio frequency device with a gallium oxide back barrier structure, the epitaxial structure of which comprises a substrate, a β-Ga2O3 buffer layer and a GaN channel layer grown on the substrate in sequence; a source electrode and a drain electrode are respectively deposited at both ends of the surface of the GaN channel layer away from the β-Ga2O3 buffer layer.
[0008] An AlN insertion layer and an InAlN barrier layer are sequentially grown on the GaN channel layer between the source electrode and the drain electrode, and a gate electrode is deposited on the InAlN barrier layer; the source electrode, the gate electrode and the drain electrode are arranged at intervals; a passivation layer is arranged on the surface of the InAlN barrier layer between the gate electrode and the drain electrode and on the surface of the InAlN barrier layer between the gate electrode and the source electrode.
[0009] The GaN channel layer and the InAlN barrier layer form an InAlN / GaN heterojunction, the GaN channel layer is close to one side of the InAlN barrier layer, and a two-dimensional electron gas (2DEG) is induced to be generated; the two-dimensional electron gas (2DEG) conductive path is a channel (Channel); and the β-Ga2O3 buffer layer forms a back barrier layer.
[0010] Further, the source electrode and the drain electrode are ohmic contact with the GaN channel layer and connect the 2DEG in the channel; and the gate electrode is Schottky contact with the InAlN barrier layer.
[0011] Further, the InAlN barrier layer is donor doped, and the background carrier concentration is 1×10 16 cm -3 ; the material of the InAlN barrier layer is In 0.17 Al 0.83 N; the material of the GaN channel layer is GaN; and the InAlN barrier layer and the GaN channel layer form a lattice match.
[0012] Further, the material of the β-Ga2O3 buffer layer is β-Ga2O3.
[0013] Further, the material of the passivation layer is Si3N4.
[0014] Further, the thickness of the substrate is 2μm;
[0015] The thickness of the β-Ga2O3 buffer layer is 1.4 μm;
[0016] The thickness of the GaN channel layer is 30 nm;
[0017] The thickness of the AlN insertion layer is 1 nm;
[0018] The thickness of the InAlN barrier layer is 10 nm;
[0019] The thickness of the passivation layer is 500 nm;
[0020] The distance between the gate and the source is 0.5 μm, the distance between the gate and the drain is 2 μm, and the length of the gate is 200 nm.
[0021] The present application has the following beneficial effects:
[0022] 1) The present application improves the device performance by introducing a β-Ga2O3 buffer layer as a natural back barrier, which reduces the leakage current and provides a robust electron confinement in the 2DEG channel, significantly reduces the leakage current and improves the DC and RF characteristics of the device, which is in sharp contrast to the traditional structure with a GaN buffer layer, and realizes the overall optimization of the device performance.
[0023] 2) The present application uses InAlN that matches the GaN lattice to form a heterojunction, which can avoid the problems of epitaxial stress and defects from the root, and significantly improves the material quality and device reliability. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1 is a layer structure schematic diagram of an InAlN / GaN HEMT device with a gallium oxide back barrier layer according to an embodiment of the present application;
[0025] Figure 2 is a layer structure schematic diagram of a traditional InAlN / GaN HEMT device without a gallium oxide back barrier layer;
[0026] Figure 3 is a transfer characteristic simulation diagram of two HEMT devices with and without a gallium oxide back barrier layer at a drain voltage of 5V according to the present application.
[0027] Figure 4 is an output characteristic simulation diagram of two HEMT devices with and without a gallium oxide back barrier layer at a gate voltage of 2V according to the present application.
[0028] Figure 5These are simulation graphs of the analog radio frequency (RF) performance of two HEMT devices at a 5V drain voltage: one with a gallium oxide back barrier and the other without. In the simulation graph, A represents the gate voltage-current gain cutoff frequency, and B represents the gate voltage-power gain cutoff frequency. Detailed Implementation
[0029] The technical solution of the present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described.
[0030] Example 1
[0031] This embodiment provides an InAlN / GaN HEMT device with a gallium oxide back barrier structure. The HEMT device uses a β-Ga2O3 buffer layer as a natural back barrier instead of a traditional GaN buffer layer to enhance electron confinement and improve device performance. The epitaxial structure of the InAlN / GaN HEMT device with a gallium oxide back barrier structure includes: a substrate, a β-Ga2O3 buffer layer, a GaN channel layer, an AlN insertion layer, and an InAlN barrier layer; the HEMT device also includes a passivation layer and a gate (G), source (S), and drain (D).
[0032] like Figure 1 As shown, a β-Ga2O3 buffer layer and a GaN channel layer are sequentially grown on the substrate. A source and a drain are deposited at both ends of the GaN channel layer surface away from the β-Ga2O3 buffer layer, respectively. An AlN insertion layer and an InAlN barrier layer are sequentially grown on the GaN channel layer between the source and drain. A gate is deposited on the InAlN barrier layer. The source, gate, and drain are spaced apart. Passivation layers are formed on the surfaces of the InAlN barrier layers between the gate and drain, and between the gate and source. The GaN channel layer and the InAlN barrier layer form an InAlN / GaN heterojunction. A two-dimensional electron gas (2DEG) is induced to form on the side of the GaN channel layer closest to the InAlN barrier layer. The conductive path of the 2DEG is a channel. The β-Ga2O3 buffer layer forms a back barrier layer; the source and drain are ohmic contacts with the GaN channel layer, connecting the 2DEG in the channel; the gate is a Schottky contact with the InAlN barrier layer.
[0033] The substrate material is SiC, with a thickness of 2 μm. The β-Ga₂O₃ buffer layer is made of β-Ga₂O₃ and has a thickness of 1.4 μm. The GaN channel layer is made of GaN and has a thickness of 30 nm. The AlN insertion layer is made of AlN and has a thickness of 1 nm. The InAlN barrier layer is donor-doped, with a background carrier concentration of 1 × 10⁻⁶. 16 cm -3 The material of the InAlN barrier layer is In0.17 Al 0.83 The InAlN barrier layer has an N and In content of 0.17% and an Al content of 0.83%, with a thickness of 10 nm. The InAlN barrier layer forms a lattice match with the GaN channel layer. The distance between the gate and source is 0.5 μm, the distance between the gate and drain is 2 μm, and the gate length is 200 nm. The passivation layer is made of Si3N4 and has a thickness of 500 nm. Using a Si3N4 thin film to passivate the device surface reduces current collapse in HEMTs. The gate material is a Ni / Au stack (Ni forms a Schottky junction with a group III nitride semiconductor, and Au acts as a protective layer to prevent oxidation). Both the source and drain materials are Ti / Al / Ni / Au stacks (formed as low-resistance ohmic contacts after rapid thermal annealing. Ti and Al are key to forming the ohmic contact, Ni acts as a diffusion barrier layer, and Au acts as a protective layer).
[0034] The fabrication methods of GaN-based HEMT RF devices with gallium oxide back barrier structures and their comparative devices (traditional structure devices, InAlN / GaN HEMT devices without gallium oxide back barrier layers) are as follows:
[0035] The fabrication method is based on mature semiconductor processes. First, functional layers are sequentially epitaxially grown on a SiC substrate using MOCVD or MBE technology. For GaN-based HEMT RF devices with a gallium oxide back barrier structure (such as…),… Figure 1 As shown), first, a β-Ga2O3 buffer layer (approximately 1.4 μm) is grown, followed by the sequential growth of a GaN channel layer (approximately 30 nm), an AlN insertion layer (approximately 1 nm), and an InAlN barrier layer (approximately 10 nm, In composition 0.17); for InAlN / GaNHEMT devices without a gallium oxide back barrier layer (such as... Figure 2 As shown in the diagram, an AlN nucleation layer (approximately 80 nm) is first grown, followed by a GaN channel layer and subsequent layers with the same structure. After epitaxial growth, device patterning and electrode fabrication are performed: mesa isolation is achieved through ICP etching to define the active region of the device; then, the source and drain regions are defined by photolithography, and a Ti / Al / Ni / Au ohmic contact metal stack is deposited and annealed; next, the gate region is defined by photolithography, and Ni / Au metal is deposited to form a Schottky gate; then, a Si3N4 layer (approximately 500 nm) is deposited on the device surface using PECVD for passivation; finally, the passivation layer openings are etched to create metal pinholes and complete the interconnect.
[0036] To verify the advantages of the InAlN / GaN HEMT device with a gallium oxide buffer layer acting as a natural back barrier structure proposed in this invention compared with the InAlN / GaN HEMT device without a gallium oxide back barrier layer, the relevant performance indicators of the two were simulated and compared. In the InAlN / GaN HEMT device without a gallium oxide back barrier layer, the AlN nucleation layer thickness is 80nm to reduce lattice mismatch.
[0037] The performance of a conventional HEMT device without a gallium oxide back barrier and the proposed HEMT device with a gallium oxide back barrier were compared using the Atlas two-dimensional device simulation tool in Silvaco TCAD. In the two-dimensional numerical calculations, the drift-diffusion transport model and several other important physical models were used, such as low-field electron mobility, high-field mobility, the Shockley-Read-Hall recombination model (SRH), Auger recombination, and polarization. Piezoelectric polarization parameters and spontaneous polarization parameters were also set. Based on small-signal AC simulations, the frequency characteristics of the device were discussed.
[0038] Figure 3 Simulation diagrams of the transfer characteristics of two HEMT devices proposed in this application, one with a gallium oxide back barrier and the other without, are shown at a drain voltage of 5V. According to... Figure 3 As can be seen, compared with traditional HEMTs without a gallium oxide back barrier, the HEMT device with a gallium oxide back barrier proposed in this invention exhibits a transconductance improvement of approximately 290 mS / mm. This is due to the ultra-wide bandgap characteristics of β-Ga₂O₃ creating a significant conduction band shift between it and the GaN channel layer. This high barrier effectively enhances the quantum confinement of the two-dimensional electron gas in the channel, significantly suppressing carrier scattering and leakage to the buffer layer. This, in turn, improves the effective mobility and transport efficiency of carriers.
[0039] Figure 4 These are simulation diagrams of the output characteristics of two HEMT devices, one with a gallium oxide back barrier and the other without, at a gate voltage of 2V. Figure 4 As shown, compared with HEMTs without a gallium oxide back barrier, HEMTs with a gallium oxide back barrier have an output current that is increased by approximately 300 mA / mm. This demonstrates that the gallium oxide back barrier effectively suppresses carrier leakage and current collapse problems commonly found in traditional GaN buffer layers. It confines electrons more efficiently within the channel, thereby significantly improving the device's current output capability.
[0040] The radio frequency (RF) performance of two HEMT devices with and without a gallium oxide back barrier at a Vds (drain-source voltage) of 5V is as follows: Figure 5As shown, HEMT devices with a β-Ga2O3 buffer layer acting as a natural back barrier benefit from the ultra-wide bandgap of β-Ga2O3, thus improving the device's RF performance. Figure 5 It is evident that the device with a gallium oxide back barrier layer achieved a peak current gain cutoff frequency of 158 GHz and a peak power gain cutoff frequency of 344 GHz, both higher than traditional HEMT devices without a gallium oxide back barrier. This is because the ultra-wide bandgap of β-Ga₂O₃ forms a deep potential well, tightly confining the conductive two-dimensional electron gas within the GaN channel. Combined with its low lattice mismatch characteristics, this significantly improves electron mobility. Simultaneously, this structure effectively reduces gate-drain parasitic capacitance and buffer layer leakage current. Thanks to the high transconductance resulting from these optimizations, the device ultimately achieved significant breakthroughs in current gain and power gain cutoff frequencies.
[0041] Based on Atlas drift-diffusion simulation results, this invention verifies the lattice-matched In using gallium oxide back barrier. 0.17 Al 0.83 The feasibility of the N / AlN / GaN HEMT scheme was demonstrated. Simulation analysis showed that the gallium oxide back barrier effectively enhances electron confinement within the channel, which is key to improving device performance. Furthermore, compared to traditional buffer layer materials, the gallium oxide back barrier exhibits superior thermal conductivity in certain crystal orientations, contributing to improved thermal management capabilities and thus enhancing reliability under high-temperature, high-power operating conditions. Therefore, this structure is conducive to the development of GaN-based RF devices.
[0042] Some steps in the embodiments of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A GaN-based HEMT radio frequency device with a gallium oxide back barrier structure, characterized in that, Its epitaxial structure includes a substrate on which a β-Ga2O3 buffer layer and a GaN channel layer are sequentially grown; a source and a drain are deposited at both ends of the surface of the GaN channel layer away from the β-Ga2O3 buffer layer; an AlN insertion layer and an InAlN barrier layer are sequentially grown on the GaN channel layer between the source and the drain, and a gate is deposited on the InAlN barrier layer. The source, gate, and drain are spaced apart; passivation layers are provided on the surface of the InAlN barrier layer between the gate and drain, and on the surface of the InAlN barrier layer between the gate and the source. The GaN channel layer and the InAlN barrier layer form an InAlN / GaN heterojunction. The GaN channel layer near the InAlN barrier layer induces the generation of a two-dimensional electron gas 2DEG. The β-Ga2O3 buffer layer forms a back barrier layer.
2. The GaN-based HEMT RF device according to claim 1, characterized in that, The source and drain are in ohmic contact with the GaN channel layer; the gate is in Schottky contact with the InAlN barrier layer.
3. The GaN-based HEMT RF device according to claim 1, characterized in that, The InAlN barrier layer is donor-doped with a background carrier concentration of 1×10⁻⁶. 16 cm -3 The material of the InAlN barrier layer is In 0.17 Al 0.83 N; The GaN channel layer material is GaN; The InAlN barrier layer and the GaN channel layer form a lattice match.
4. The GaN-based HEMT RF device according to claim 1, characterized in that, The material of the β-Ga2O3 buffer layer is β-Ga2O3.
5. The GaN-based HEMT RF device according to claim 1, characterized in that, The passivation layer is made of Si3N4.
6. The GaN-based HEMT RF device according to claim 1, characterized in that, The substrate thickness is 2 μm; The thickness of the β-Ga2O3 buffer layer is 1.4 μm; The thickness of the GaN channel layer is 30 nm; The thickness of the AlN insertion layer is 1 nm; The thickness of the InAlN barrier layer is 10 nm; The passivation layer has a thickness of 500 nm; The distance between the gate and the source is 0.5 μm, the distance between the gate and the drain is 2 μm, and the length of the gate is 200 nm.