An Improved Method for Establishing a Large-Signal Model for ASM-HEMT GaN Devices

Abstract

The application discloses a method for establishing an improved ASM-HEMT GaN device large signal model, and based on a physical base ASM-HEMT model, an improved direct current characteristic model is provided for a wide band gap semiconductor radio frequency GaN HEMT, the influence of drain-source voltage (V ds ), gate-source voltage (V gs ) on the current collapse and kink effect of the output characteristic curve at a low drain-source voltage is considered, and the formula of drain-source current (I ds ) in the ASM-HEMT is modified. The application extracts the direct current characteristic model parameters by testing a GaN HEMT device with a single gate finger, a gate width of 200 um and a gate finger number of 6 through a chip test. The extraction result shows that the direct current characteristic model provided by the application accurately describes the current collapse and kink effect of the device at a low drain-source voltage, accurately fits the corresponding drain-source voltage value when the kink effect occurs under different gate-source voltages, optimizes the transition zone from the linear zone to the saturation zone in the output characteristic, and verifies that the improved direct current characteristic model based on the ASM-HEMT accurately represents the current-voltage (IV) characteristics of the GaN HEMT device in the whole working area.

Description

Technical Field

[0001] This invention relates to the field of modeling third-generation wide-bandgap semiconductor radio frequency GaN HEMT devices, and in particular to an improved method for establishing a large-signal model of ASM-HEMT GaN devices. Background Technology

[0002] With the increasing demand for GaN HEMTs (High Electron Mobility Transistors) in radio frequency and power electronics, GaN HEMT device models have become a research hotspot in recent years, mainly including behavioral basis models, empirical basis models, and physical basis models. Because physical basis models effectively combine the physical structure and actual operating effects of the device, thus obtaining accurate and continuous equations for drain-source current and intrinsic capacitance, they have gradually become the mainstream GaN HEMT device models. Among them, ASM-HEMT based on surface potential has been certified as the standardized model for GaN HEMT devices. However, ASM-HEMT does not yet consider the drain-source voltage Vo. ds Gate-source voltage V gs The influence of current collapse and the Kink effect at low drain-source voltages results in a large fitting error in the model transitioning from the linear region to the saturation region, making it difficult to meet the requirements of accurate circuit design. Summary of the Invention

[0003] Objective of the invention: This invention proposes an improved method for establishing a large-signal model of ASM-HEMTGaN devices, which accurately fits V... ds V gs The effects of current collapse and kink effect were mitigated, enabling a smooth transition from the linear region to the saturation region, thus accurately characterizing the DC characteristics of GaN HEMT devices throughout the entire operating region.

[0004] Technical solution: This invention proposes an improved method for establishing a large-signal model of an ASM-HEMT GaN device, comprising the following steps:

[0005] (1) Add the drain-source voltage V to the ASM-HEMT drain-source current formula in the physical basis. ds Effects on current collapse and the kink effect;

[0006] (2) Introduce a correction coefficient CK into the drain-source current formula in step (1);

[0007] (3) Establish the polynomial relationship between the drain-source voltage and the gate-source voltage when the kink effect occurs in step (2);

[0008] (4) The established GaN HEMT DC characteristic model was verified by performing on-wafer testing on the GaN HEMT device.

[0009] Preferably, in step (1), the ASM-HEMT model obtains the expression for the Fermi level potential corresponding to 2DEG at the GaN / AlGaN heterojunction by solving the Schrödinger equation and the Poisson equation, and obtains the surface potentials of the source and drain. Based on the carrier drift diffusion mechanism and combined with the real physical effects of the GaN HEMT device, the drain-source current equation is obtained.

[0010] Preferably, in step (1), the Schrödinger equation and the Poisson equation are solved to establish the Fermi level potential V corresponding to 2DEG in the GaN / AlGaN heterojunction triangular potential well. f The expression is:

[0011]

[0012]

[0013] Among them, V go H(V) is the effective gate voltage. go,eff ) is related to V go Related functions, C g It is the gate capacitance per unit area, q is the unit charge, D is the 2DEG density of states, and V is the gate capacitance per unit area. th It is thermal voltage, V off This is the cutoff voltage; eta0 and vdscale are the fitting parameters for the leakage inductive barrier reduction effect. V dsx It is V ds The correction value, V ds It is the drain-source voltage. Preferably, in step (1), the source surface potential... Drain surface potential for:

[0014]

[0015]

[0016] Among them, V s It is the source voltage, V d,eff It is the effective drain voltage.

[0017] Preferably, in step (1), the drain-source current I ds The expression is:

[0018]

[0019]

[0020] Where W is the gate width, L is the gate length, and n f It is the gate index, μ eff It is the effective mobility, θsat It is a parameter related to saturation voltage, V tv It is V th The correction value, λ, is the fitting parameter for the channel length modulation effect.

[0021] Preferably, step (2) introduces a correction coefficient CK, which adjusts the V in equation (2). go Make corrections:

[0022]

[0023] CK = d0 * tanh[d1 * (V ds -V ds-k (8)

[0024] In the formula, d0 and d1 are the fitting parameters, and V ds-k It is the drain-source voltage value corresponding to the occurrence of the kink effect.

[0025] Preferably, the drain-source voltage value corresponding to the occurrence of the kink effect in step (3) has a polynomial relationship with the gate-source voltage. Therefore, V in equation (8) is... ds-k Rewritten as:

[0026] V ds-k = g0 + g1 * Vgs + g2 * Vgs 2 +g3*Vgs 3 +g4*Vgs 4 +……(9)

[0027] Among them, g0, g1, g2, g3, g4, etc. are fitting parameters.

[0028] Preferably, in step (4), the GaN HEMT device has a single-finger gate width of 200um and a gate finger number of 6; in step (4), the DC characteristics of the established GaN HEMT DC characteristic model are verified, including output characteristics, output transconductance, transfer characteristics and transconductance.

[0029] Beneficial effects: (1) This invention adds drain-source voltage V to the physical basis ASM-HEMT drain-source current formula. ds The effects of current collapse and the Kink effect are described by introducing a correction coefficient CK into the drain-source current formula.

[0030] (2) This invention adds the gate-source voltage V to the physical basis ASM-HEMT drain-source current formula. gs To investigate the influence of the drain-source voltage corresponding to the occurrence of the kink effect, a polynomial relationship between the drain-source voltage and the gate-source voltage corresponding to the occurrence of the kink effect is established, thereby achieving accurate fitting of the drain-source voltage corresponding to the occurrence of the kink effect under different gate-source voltages.

[0031] (3) This invention adds the drain-source voltage V to the physical basis ASM-HEMT drain-source current formula. ds Gate-source voltage V gs The influence of current collapse and the kink effect was described. Accurate fitting of the drain-source voltage values ​​corresponding to the occurrence of the kink effect under different gate-source voltages was achieved, successfully realizing a smooth transition from the linear region to the saturation region.

[0032] (4) Based on the physical ASM-HEMT model, this invention improves the drain-source current formula and finally proposes a DC characteristic model that can accurately characterize the IV characteristics of GaN HEMT devices throughout the entire operating region, thereby reducing circuit design costs and improving power amplifier performance. Attached Figure Description

[0033] Figure 1 The output characteristic curve of a GaN HEMT device exhibiting current collapse and kink effect at low drain-source voltage;

[0034] Figure 2 To improve the model's fitting results for current collapse and the kink effect at low drain-source voltages;

[0035] Figure 3 To improve the output characteristic curve I of the model ds -V ds Fitting results graph;

[0036] Figure 4 To improve the output transconductance g of the model ds1 -V ds Fitting results graph;

[0037] Figure 5 To improve the model's transfer characteristic curve I ds -V gs Fitting results graph;

[0038] Figure 6 To improve the transconductance g of the model m1 -V gs The fitting results are shown in the figure. Detailed Implementation

[0039] I. Physical basis ASM-HEMT model drain-source current I ds Formula introduction

[0040] The ASM-HEMT model obtains the expression for the Fermi level potential corresponding to 2DEG at the GaN / AlGaN heterojunction by solving the Schrödinger equation and the Poisson equation, and then obtains the surface potentials of the source and drain. At the same time, based on the carrier drift and diffusion mechanism and combined with the real physical effects of GaN HEMT devices, the drain-source current equation is finally obtained.

[0041] Solving the Schrödinger and Poisson equations, the Fermi level potential V corresponding to 2DEG in the GaN / AlGaN heterojunction triangular potential well is established. f The expression is:

[0042]

[0043]

[0044] Among them, V go H(V) is the effective gate voltage. go,eff ) is related to V go Related functions, C g It is the gate capacitance per unit area, q is the unit charge, D is the 2DEG density of states, and V is the gate capacitance per unit area. th It is thermal voltage, V off This is the cutoff voltage; eta0 and vdscale are the fitting parameters for the leakage inductive barrier reduction effect. V dsx It is V ds The correction value, V ds It is the drain-source voltage.

[0045] Therefore, the source surface potential Drain surface potential It can be represented as:

[0046]

[0047]

[0048] Among them, V s It is the source voltage, V d,eff It is the effective drain voltage.

[0049] Based on the carrier drift-diffusion mechanism and combined with the actual physical effects of the device, the drain-source current I is obtained. ds The expression is:

[0050]

[0051]

[0052] Where W is the gate width, L is the gate length, and n f It is the gate index, μ effIt is the effective mobility, θ sat It is a parameter related to saturation voltage, V tv It is V th The correction value, λ, is the fitting parameter for the channel length modulation effect.

[0053] II. Effective Modeling of Current Collapse and Kink Effect

[0054] Low V in the output characteristic curve of GaN HEMT device ds At this location, there is a significant current collapse Kink effect, such as Figure 1 As shown (circular areas represent current collapse, square areas represent the kink effect), the 2DEG at the channel is trapped by defects, reducing carrier concentration and thus the drain-source current, i.e., current collapse. With V... ds As the electric field intensity continues to increase, the defect releases trapped electrons that gain energy and thus increase their kinetic energy, leading to a rapid increase in the drain-source current again, i.e., the Kink effect. To accurately simulate current collapse and the Kink effect, a correction coefficient CK is introduced to adjust V in equation (2). go Make corrections:

[0055]

[0056] CK = d0 * tanh[d1 * (V ds -V ds-k (8)

[0057] Among them, d0 and d1 determine the degree of current collapse and the steepness of the drain-source current rise when the Kink effect occurs, V ds-k It is the drain-source voltage value corresponding to the occurrence of the kink effect.

[0058] III. Enhancing the control capability of gate-source voltage over 2DEG in the channel

[0059] In different V gs Under bias, different longitudinal electric field strengths lead to different degrees of electron capture and release, resulting in different drain-source voltage values ​​corresponding to the occurrence of the Kink effect. The drain-source voltage value corresponding to the occurrence of the Kink effect has a polynomial relationship with the gate-source voltage, therefore, V in equation (8) ds-k Rewritten as:

[0060] V ds-k = g0 + g1 * Vgs + g2 * Vgs 2 +g3*Vgs 3 +g4*Vgs 4 +……(9)

[0061] Among them, g0, g1, g2, g3, g4, etc. are fitting parameters that determine the drain-source voltage values ​​corresponding to the occurrence of the kink effect under different gate-source voltages.

[0062] IV. Verification of GaN HEMT DC Characteristic Model

[0063] This invention performs on-wafer testing on a 6×200µm GaN HEMT device, obtaining IV characteristic test data using IVCAD software. An improved DC characteristic model is implemented using Verilog-A code and simulated on ICCAP 2020 software to obtain IV characteristic simulation data. The IV characteristics mainly include output characteristics and output transconductance (output characteristic curve versus V). ds First derivative), transfer properties and transconductance (transfer property curve versus V) gs (first derivative), the fitting result is as follows Figures 2-6 As shown. The operating condition for the output characteristics is the drain-source voltage V. ds =0~36V, step size step=0.2V, gate-source voltage V gs = -4.0~0V, step size step=0.2V; the operating condition for output transconductance is drain-source voltage V ds =0~36V, step size step=0.2V, gate-source voltage V gs = -1.2V; the operating conditions for transfer characteristics and transconductance are the gate-source voltage V. gs = -4 to 0V, step size step = 0.1V, drain-source voltage V ds =4V, 28V.

[0064] The fitting results show that the fitting error of the IV characteristics is within 3%, indicating that the improved DC characteristic model accurately describes the current collapse and the kink effect, accurately fits the drain-source voltage values ​​corresponding to the occurrence of the kink effect under different gate-source voltages, optimizes the transition region from the linear region to the saturation region, accurately characterizes the IV characteristics of the GaN HEMT device throughout the entire operating range, and further verifies its engineering application value.

Claims

1. An improved method for establishing a large-signal model of an ASM-HEMT GaN device, characterized in that, Includes the following steps: (1) Add the drain-source voltage to the ASM-HEMT drain-source current formula in the physical basis. V ds The effects on current collapse and the Kink effect; in step (1), the Schrödinger equation and the Poisson equation are solved to establish the Fermi level potential corresponding to 2DEG in the GaN / AlGaN heterojunction triangular potential well. V f The expression is: (1) (2) in, V go The effective gate voltage, V gs Gate-source voltage, H(V go,eff ) Is with V go Related functions, C g It is the gate capacitance per unit area. q It is a unit charge. D It is the 2DEG density of states. V th It is thermal voltage. V off It is the cutoff voltage. eta0 , vdscale These are the fitting parameters for the leakage inductive barrier reduction effect. , V dsx yes V ds The correction value, V ds It is the drain-source voltage; Source surface potential φ s Drain surface potential φ d for: (3) (4) in, V s It is the source voltage. V d,eff It is the effective drain voltage; Drain source current I ds The expression is: (5) (6) in, W It is the grid width. L It is the grid length. n f It is the grid index. μ eff It is the effective migration rate. θ sat These are parameters related to saturation voltage. V tv yes V th The correction value, λ These are the fitting parameters for the channel length modulation effect. φ m =( φ s + φ d ) / 2, φ ds = φ d - φ s ; (2) Introduce a correction factor into the drain-source current formula in step (1). CK Step (2) introduces a correction factor. CK For equation (2) V go Make corrections: (7) (8) In the formula d 0、 d 1 represents the fitted parameter. V ds-k This is the drain-source voltage value corresponding to the occurrence of the kink effect; (3) Establish the polynomial relationship between the drain-source voltage and the gate-source voltage when the kink effect occurs in step (2); the drain-source voltage value and the gate-source voltage when the kink effect occurs in step (3) have a polynomial relationship, therefore, the value in equation (8) V ds-k Rewritten as: (9) in, g0 , g 1. g 2. g 3. g 4 is the fitting parameter; (4) The established GaN HEMT DC characteristic model was verified by performing on-wafer testing on the GaN HEMT device.

2. The improved method for establishing a large-signal model of an ASM-HEMT GaN device according to claim 1, characterized in that, In step (1), the ASM-HEMT model obtains the expression for the Fermi level potential corresponding to 2DEG at the GaN / AlGaN heterojunction by solving the Schrödinger equation and the Poisson equation, and obtains the surface potentials of the source and drain. Based on the carrier drift diffusion mechanism and combined with the real physical effects of GaN HEMT devices, the drain-source current equation is obtained.

3. The improved method for establishing a large-signal model of an ASM-HEMT GaN device according to claim 1, characterized in that, In step (4), the GaN HEMT device has a single-finger gate width of 200um and a gate finger number of 6; the DC characteristics of the established GaNHEMT DC characteristic model are verified, including output characteristics, output transconductance, transfer characteristics and transconductance.

4. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 3.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 3.

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