A pulse laser equivalent heavy ion irradiation theoretical simulation method and system

Abstract

The application discloses a kind of pulse laser equivalent heavy ion irradiation theoretical simulation method and system, belong to pulse laser simulation single particle effect test field.It is with GaN HEMT sensitive area inside laser-induced non-equilibrium carrier peak concentration equal to heavy ion track center peak concentration as criterion: account for multilayer interface transmission, Gaussian beam propagation and single-photon absorption, seek ultraviolet pulse laser carrier peak concentration;According to LET, material density, electron-hole pair generation energy and track radius, the peak concentration of columnar distribution is solved;Make both equal to establish pulse energy and LET mapping and back-propagation equivalent LET, and then be corrected by space constraint factor and charge collection efficiency, and be calibrated by simulation and heavy ion measurement.The application mechanism is clear, high precision, and is suitable for space use gallium nitride and other wide band gap semiconductor devices radiation resistance evaluation and reinforcement.

Description

Technical Field

[0001] This invention belongs to the field of pulsed laser simulation of single-event effect testing technology, specifically relating to a theoretical simulation method and system for pulsed laser equivalent heavy ion irradiation. Background Technology

[0002] Gallium nitride (GaN)-based high electron mobility transistors (HETTs), with their high breakdown voltage, low on-resistance, and excellent high-frequency characteristics inherent in wide-bandgap semiconductor materials, are gradually becoming core devices for power conversion and energy management in next-generation spacecraft. However, high-energy heavy ions, which are widely present in the space environment, can penetrate device packaging and deposit high-density ionized charges in sensitive areas, thereby inducing single-event transients or even single-event burn-out, seriously threatening the reliability of space power supplies and the safety of on-orbit missions. Therefore, accurately assessing the single-event immunity of GaN-based HETTs during the ground phase is an indispensable part of the hardening design of aerospace-grade electronic systems.

[0003] Currently, the authoritative method for assessing the single-event sensitivity of devices still relies on ground-based simulations at heavy-ion accelerators. However, heavy-ion accelerator testing is extremely time-constrained and costly per run. Furthermore, the beam size of heavy-ion accelerators is typically on the order of millimeters or even centimeters, making it difficult to precisely target and irradiate sensitive regions at the micrometer scale inside gallium nitride-based high electron mobility transistors (such as the gate-drain electric field peak region and the p-type gallium nitride gate region) and analyze damage mechanisms. In addition, accelerator testing has long cycles and poor flexibility, making it difficult to conduct single-event effect studies on devices under real-world conditions such as dynamic switching, cryogenic environments, and multi-stress coupling.

[0004] Pulsed laser simulation of single-event effects (SEE) technology offers significant advantages such as low cost, no radiation source, spatial resolution down to the micrometer scale, and continuously adjustable parameters, making it a promising supplement to, and even a partial replacement for, heavy-ion accelerators. However, the energy deposition mechanism of lasers in semiconductors (primarily single-photon or two-photon absorption, forming a three-dimensional Gaussian photogenerated carrier distribution) differs fundamentally from the Coulomb ionization mechanism of heavy ions (forming a one-dimensional columnar high-density track along the incident path). Traditional equivalent methods mostly use the equality of total photogenerated carriers or total deposited charge as the criterion. However, in the SEE effect of gallium nitride-based high-electron-mobility transistors, the physical triggering threshold for burnout often depends on whether the local non-equilibrium carrier concentration exceeds a certain critical value, such as triggering phonon-plasma instability or avalanche injection under a high electric field, rather than on the total charge. Therefore, the total charge equivalence method exhibits significant deviations near the SEE threshold, sometimes exceeding an order of magnitude, making it difficult to meet the requirements for refined evaluation of the radiation resistance performance of aerospace power devices. Summary of the Invention

[0005] The technical problem to be solved by this invention is that most existing pulsed laser simulation single-event effects techniques use the equality of total photogenerated carriers or total deposited charge as the equivalence criterion between laser and heavy ions. However, the physical triggering threshold for single-event burnout of gallium nitride-based high electron mobility transistor devices depends on whether the local non-equilibrium carrier concentration exceeds the critical value, rather than on the total charge. This causes the total charge equivalence method to deviate significantly near the single-event burnout threshold and has unclear physical meaning, making it unable to support the refined evaluation of the radiation resistance performance of aerospace power devices.

[0006] To address the aforementioned technical problems, this invention provides a theoretical simulation method for pulsed laser equivalent heavy ion irradiation, comprising the following steps: Step S1: Determine the parameters of the GaN HEMT device and the laser parameters. The parameters of the GaN HEMT device include the layered structure of the GaN HEMT device, the material and doping of each layer, and the laser parameters include the laser wavelength, pulse energy, pulse width and focused spot waist radius. Step S2: Establish the three-dimensional spatial distribution of non-equilibrium carriers generated by pulsed laser within the semiconductor material of the GaN HEMT device, and calculate the laser-induced peak carrier concentration based on the laser parameters and the optical properties of the semiconductor material; Step S3: Establish a columnar distribution of non-equilibrium carriers generated by heavy ions along the track in the semiconductor material, and calculate the peak carrier concentration induced by heavy ions based on the linear energy transfer (LET) value of heavy ions and the characteristics of the semiconductor material. Step S4: Using the laser-induced peak carrier concentration being equal to the heavy ion-induced peak carrier concentration as an equivalence criterion, establish a mapping relationship between the pulse energy of the pulsed laser and the linear energy transfer value of the heavy ions, and based on the mapping relationship, deduce the equivalent linear energy transfer value from the given pulse energy, or deduce the required pulse energy from the given linear energy transfer value.

[0007] Preferably, the calculation of the laser-induced peak carrier concentration includes: calculating the pulse peak power based on the laser parameters and the complex refractive index and absorption coefficient of each layer of the GaN HEMT device, considering the interfacial transmission of the multilayer heterostructure and the propagation of the Gaussian beam in the medium. On-axis incident peak light intensity Incident light intensity entering semiconductor materials ,depth Waist radius at the point Light intensity distribution inside semiconductor materials Absorbed power density Pulse absorbed energy density and photogenerated carrier concentration : ; ; ; ; ; ; ; ; and take The maximum value is taken as the laser-induced peak carrier concentration. ; Rayleigh length Single photon energy , For pulse energy, The pulse width. To focus the beam's waist radius, The total transmittance of the multilayer heterostructure is . Let be the real part of the complex refractive index of the semiconductor material. The single-photon absorption coefficient is... The wavelength of the laser. Let be Planck's constant. The speed of light in a vacuum Radial coordinates, These are depth coordinates.

[0008] Preferably, the calculation of the heavy ion-induced peak carrier concentration includes: calculating the carrier linear density per unit length based on the linear energy transfer value of the heavy ions, the material density, and the average energy required to generate one electron-hole pair. : ; Then, combining the heavy ion track radius, and assuming a uniform or Gaussian carrier distribution within the track, the peak carrier concentration at the track center is calculated. : ; in For material density, The linear energy transfer value for heavy ions. The average energy required to generate an electron-hole pair denoted as the heavy ion track radius.

[0009] Preferably, the laser-induced carrier distribution calculation is performed based on the single-photon absorption and two-photon absorption involved in the laser absorption process: Introducing single-photon absorption coefficient With two-photon absorption coefficient ; For the case where single-photon absorption is dominant, the light intensity along the depth satisfies Photogenerated carrier generation rate ; For cases where two-photon absorption is not negligible, numerical solutions to the coupling equations are required. and And perform spatiotemporal integration by combining the pulse time waveform; in For light intensity, For single photon energy, Photogenerated carrier concentration, Photogenerated carrier generation rate For depth coordinates, For time.

[0010] Preferably, the method further includes correcting the laser-induced peak carrier concentration by introducing a space constraint factor and a charge collection efficiency, wherein the space constraint factor characterizes the proportion of carriers falling within the sensitive region of the device, and the charge collection efficiency characterizes the proportion of charge effectively collected by the electrodes, and the corrected peak carrier concentration is: Among them, spatial constraint factor , The peak carrier concentration induced by laser. This is the corrected peak carrier concentration. The horizontal radius of the sensitive area. To focus the beam's waist radius, For charge collection efficiency; The modified peak carrier concentration is used in solving the equivalent criterion.

[0011] Preferably, the method further includes using semiconductor simulation software to establish a structural mesh and physical model for the GaN HEMT device, wherein the physical model includes a carrier recombination model, a mobility model, a polarization effect model, and a trap model; Ultraviolet pulsed laser irradiation and heavy ion irradiation were applied respectively to extract the carrier concentration distribution and electrical characteristics near the surface of the device. The simulated peak carrier concentration was compared with the calculated peak carrier concentration. By adjusting the model parameters, the deviation between the simulation results and the calculated results was made to fall within a set range, thereby verifying the mapping relationship and calibrating the parameters.

[0012] Preferably, the method is applied to the evaluation of single-event effects in GaN power devices for aerospace applications. By irradiating the device under test with ultraviolet pulsed laser, the pulsed laser energy is measured when the device under test experiences a single-event transient or single-event burn-up. The equivalent criterion of the peak carrier concentration is used to calculate the heavy-ion linear energy transfer threshold corresponding to the pulsed laser energy, and the single-event resistance capability of the device under test is predicted before heavy-ion accelerator experiments.

[0013] Preferably, the method further includes a model verification step: comparing the heavy ion linear energy transfer threshold obtained by laser equivalent with the linear energy transfer threshold measured on the same device on a heavy ion accelerator; when the deviation between the two exceeds a set range, adjusting the model parameters until the deviation converges; and using at least two heavy ions with different linear energy transfer values, establishing a piecewise mapping function between pulsed laser energy and heavy ion linear energy transfer value.

[0014] This invention also provides a theoretical simulation system for pulsed laser equivalent heavy ion irradiation, comprising: The parameter input module is used to input laser parameters, material parameters, and device parameters; The laser carrier distribution calculation module is used to calculate the three-dimensional spatial distribution and peak carrier concentration of non-equilibrium carriers generated by pulsed laser in semiconductor material based on the parameters input by the parameter input module. The heavy ion carrier distribution calculation module is used to calculate the columnar distribution of carriers generated by heavy ions along the track and its peak carrier concentration based on the linear energy transfer value of heavy ions and the material parameters. The equivalent mapping module is used to calculate and output the equivalent linear energy transfer value corresponding to the pulse energy, or the equivalent pulse energy corresponding to the linear energy transfer value, based on the criterion that the peak carrier concentration induced by the laser is equal to the peak carrier concentration induced by heavy ions. The simulation verification module is used to perform numerical simulation verification and parameter optimization on the results obtained by the equivalent mapping module.

[0015] Preferably, the system further includes a calibration module, which is used to perform multi-point calibration on the equivalence relationship output by the equivalence mapping module using at least two heavy ions with different linear energy transfer values, and to establish a piecewise mapping function between pulsed laser energy and heavy ion linear energy transfer value.

[0016] The beneficial effects of the present invention include at least the following: 1) This invention uses the peak carrier concentration, which is directly related to the physical triggering mechanism of single-event burnout, as the equivalence criterion. This overcomes the defect of the total charge equivalence method having too large a deviation in strong field effects such as single-event burnout, making the equivalence results more consistent with the actual triggering conditions of burnout, and the physical meaning is clear. 2) In establishing the equivalent relationship, this invention fully considers factors such as Gaussian beam propagation, multilayer heterostructure interface transmission, single-photon and two-photon absorption, as well as spatial constraint factor and charge collection efficiency, resulting in a model with high accuracy and strong adaptability. 3) This invention introduces a dual verification and multi-point calibration process consisting of numerical simulation of semiconductor devices and actual measurement of heavy ion accelerators, forming a closed loop in which theoretical calculations and experimental data mutually verify each other, ensuring the engineering usability and traceability of the method. 4) This invention is not limited to gallium nitride, but is also applicable to other wide bandgap semiconductor power devices such as silicon carbide. It can provide a low-cost, high-efficiency and physically meaningful engineering solution for rapid radiation screening, hardened design verification and space mission reliability assessment of aerospace power devices. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of the theoretical simulation method for pulsed laser equivalent heavy ion irradiation of the present invention; Figure 2 This is a schematic diagram of the layered structure of a gallium nitride-based high electron mobility transistor device in an embodiment of the present invention; Figure 3 This is a schematic diagram of the simulation modeling structure of the gallium nitride-based high electron mobility transistor device in an embodiment of the present invention; Figure 4 This is a simulation result of the electron concentration distribution within a gallium nitride-based high electron mobility transistor device after heavy ion irradiation; Figure 5 This is a simulation result of the electron concentration distribution within a gallium nitride-based high electron mobility transistor device after irradiation with ultraviolet pulsed laser. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0019] The overall estimation process of this invention is as follows: Figure 1 As shown, the process includes determining device and laser parameters, calculating laser-induced peak carrier concentration, calculating heavy-ion-induced peak carrier concentration, establishing a mapping based on the equality of the two and solving for the equivalent LET, as well as simulation verification and parameter calibration. Specifically, it includes the following steps.

[0020] Step S1: Determine the parameters of the gallium nitride-based high electron mobility transistor (GaN HEMT) device and the pulsed laser parameters.

[0021] Specifically, in this embodiment, the layered structure of a gallium nitride-based high electron mobility transistor and the material, thickness, and doping of each layer are first given, as follows: Figure 2 As shown, from bottom to top, it includes a substrate (e.g., SiC or Si, 100–500 μm thick), a GaN buffer layer (2–5 μm thick, n-type background doping concentration approximately 1 × 10⁻⁶), and a layer of GaN buffer (2–5 μm thick, n-type background doping concentration approximately 1 × 10⁻⁶). 15 ~1×10 16 cm - ³), GaN channel layer (thickness 100–300 nm), AlGaN barrier layer (thickness 10–20 nm, Al composition 0.20–0.25), and passivation layer (e.g., SiN). x A layer with a thickness of 100–200 nm is formed below the gate, and a p-type doping concentration of approximately 5 × 10⁻⁶ nm is formed below the gate. 17 cm - The p-type GaN gate region is 3; the source, gate, drain and field plate electrodes are arranged laterally, typically in the range of -2 to -1μm in the lateral coordinates, the source is located at -2 to -1μm, the gate at 1 to 2μm, the drain at 17 to 18μm, and the field plate at -1 to 4μm.

[0022] Laser parameters include vacuum wavelength. (Typical values: 355nm, 532nm, 1064nm, with 355nm preferred), pulse energy (Typical values ​​0.1–100 nJ), pulse width (Typical values ​​0.1–10 ns) and the waist radius of the focused spot (Typical values ​​are 0.5–5 μm, defined by 1 / e² strength radius).

[0023] Step S2: Establish the three-dimensional spatial distribution of non-equilibrium carriers generated by pulsed laser in the semiconductor material of GaN HEMT device, and calculate the laser-induced peak carrier concentration based on the laser parameters and the optical properties of the semiconductor material.

[0024] Specifically, based on the aforementioned laser parameters and the complex refractive index and absorption coefficient of each layer of the device material, and taking into account the interfacial transmission of the multilayer heterostructure and the propagation of the Gaussian beam within the medium, the distribution of photogenerated carriers in the sensitive region of the device is gradually determined. The complex refractive index of the material is... ,in Let be the real part of the complex refractive index. The imaginary part of the complex refractive index, i.e., the extinction coefficient, is given by... Confirmed; peak pulse power is The corresponding on-axis incident peak light intensity is After the laser beam is incident on the device surface, it undergoes Fresnel transmission and Beer-Lambert absorption at each interface, resulting in the initial intensity distribution of the light entering the gallium nitride layer as follows: ,in The total transmission coefficient of the multilayer structure can be calculated using the transmission matrix method or the layer-by-layer Fresnel formula. For radial coordinates.

[0025] Using a Gaussian beam propagation model, depth The waist radius at the point is Rayleigh length is Based on this, the light intensity distribution inside the gallium nitride layer is as follows: Furthermore, the absorbed power density Pulse absorbed energy density and combined with single photon energy ,in Let be Planck's constant. Given the speed of light in a vacuum, the concentration distribution of photogenerated carriers was obtained. The maximum value in space is the laser-induced peak carrier concentration. When the gallium nitride layer has strong absorption and the waist remains essentially constant within the absorption depth range, it can be approximated as... ,thereby The peak occurred , Place.

[0026] In one embodiment of the present invention, a single-photon absorption coefficient is introduced for both single-photon absorption and two-photon absorption involved in the laser absorption process. With two-photon absorption coefficient This needs to be addressed. When single-photon absorption is dominant... At that time, the light intensity along the depth satisfies Photogenerated carrier generation rate When the laser wavelength is greater than the wavelength corresponding to the material's bandgap and two-photon absorption cannot be ignored (e.g., 532nm or 1064nm lasers in GaN), then numerical solutions to the coupling equations are required. and And perform spatiotemporal integration by combining the time waveform of the pulse, where For light intensity, For photogenerated carrier concentration, For time.

[0027] Step S3: Establish the columnar distribution of non-equilibrium carriers generated by heavy ions along the track in the semiconductor material, and calculate the peak carrier concentration induced by heavy ions based on the linear energy transfer (LET) value of heavy ions and the characteristics of the semiconductor material.

[0028] Specifically, based on the LET value of heavy ions and material density And the average energy required to generate an electron-hole pair First, calculate the linear density of carriers per unit length. Combined with the heavy ion track radius Under the assumption of uniform or Gaussian carrier distribution within the track, the peak carrier concentration at the track center is obtained. In this embodiment, the heavy ion track radius The electron blocking ability of the material or empirical formulas can be given, but are not intended to limit the invention.

[0029] Step S4: Using the equivalence criterion that the peak carrier concentration induced by the laser is equal to the peak carrier concentration induced by heavy ions, establish a mapping relationship between the pulse energy of the pulsed laser and the linear energy transfer value of heavy ions, and deduce the equivalent linear energy transfer value from the given pulse energy based on the mapping relationship, or deduce the required pulse energy from the given linear energy transfer value.

[0030] Specifically, in this embodiment, the laser-induced peak carrier concentration is equal to the heavy-ion-induced peak carrier concentration as the equivalence criterion, that is, let This establishes a mapping relationship between the laser pulse energy parameter and the LET value of heavy ions; for a given laser parameter, the equivalent LET value can be derived, and conversely, for a given LET value, the required pulse energy can be calculated.

[0031] In another embodiment of the present invention, considering the finite size of the device's sensitive region and the recombination and collection of charge carriers, a space constraint factor is used. With charge collection efficiency Peak concentration correction: The space constraint factor characterizes the proportion of carriers falling within the sensitive region of the device, and is taken as... ,in The lateral radius of the sensitive region; charge collection efficiency Characterizing the proportion of charge effectively collected by the electrode; the corrected effective peak concentration is... The effective peak concentration is used to solve the equivalence criterion, so that the equivalent result is closer to the actual charge collection behavior of the device.

[0032] In another embodiment of the present invention, simulation verification and parameter calibration steps are also included. Specifically, a structural mesh and physical model of the GaN HEMT device are established using semiconductor device simulation software, and ultraviolet pulsed laser irradiation and heavy ion irradiation are applied respectively. During modeling, the position ranges of the source, drain, gate, and field plate electrodes are defined, and non-uniform mesh refinement is performed on the heterojunction interface, gate region, and buffer layer along the depth direction. GaN or AlGaN material and p-type GaN gate region doping are set according to the region. The physical model covers Shockley-Reed-Hall (SRH) recombination, Auger recombination, Fermi statistics, temperature-dependent mobility and low-field mobility, polarization effects including spontaneous polarization and piezoelectric polarization, and trap models in the buffer layer. An insulating gate model is enabled for the p-type GaN region. For heavy ion irradiation, the start and end points of ion incidence, track radius, LET value, and time Gaussian distribution of carrier generation rate are defined. For pulsed laser irradiation, the beam model is set according to wavelength, spot position, incident angle, and transverse Gaussian distribution. The complex refractive index of GaN and AlGaN at this wavelength is given by material statement to take into account the reflection and transmission of multilayer films. The rise, hold, and fall time waveforms of the Gaussian pulse are realized by linear ramp combination.

[0033] During the solution process, a DC bias scan is first performed to the working voltage and the steady-state structure is saved. Then, the heavy ion transient and laser transient are solved in stages according to time and the electrode transient current is recorded. Finally, the peak carrier concentration and its spatiotemporal evolution near the surface of the gallium nitride layer (including the channel and buffer layer) are extracted and compared with the theoretical calculation values ​​one by one. When the deviation between the two exceeds the set range, the model parameters are adjusted to make the simulation results consistent with the theoretical results, thereby completing the verification of the equivalence criterion and parameter calibration.

[0034] After a general description of steps S1 to S4 above, the following uses a specific GaN HEMT device as an example, employing a 355nm ultraviolet pulsed laser to simulate the heavy-ion single-particle burn-off effect. Its photon energy is approximately 3.5eV, which highly matches the bandgap of gallium nitride at approximately 3.4eV. Single-photon intrinsic absorption is dominant, but the scope of application of this invention is not limited thereto. The following embodiments will provide a detailed description of each step.

[0035] Example 1 This embodiment uses gallium nitride high-power electron mobility transistors as the subject and employs a 355nm ultraviolet pulsed laser with intrinsic single-photon absorption to simulate the heavy-ion single-particle burn-up effect, quantitatively demonstrating the peak concentration equivalence criterion. First, the input parameters are determined: laser wavelength. nm, pulse energy nJ, pulse width ns, the waist radius of the focused spot μm. Gallium nitride materials take the real part of the complex refractive index. Extinction coefficient ,Depend on The single-photon absorption coefficient is approximately m - ¹, that is, approximately cm - ¹, corresponding to an absorption depth of approximately 67.7 nm; material density g / cm³ (SiC approximately 3.2 g / cm³, Si approximately 2.33 g / cm³), single photon energy GaN has a band gap of approximately 3.4 eV, which is slightly smaller than the photon energy, so intrinsic absorption by a single photon is dominant.

[0036] The device parameters are set with a surface reflectivity of approximately 0.2 and a lateral radius of the sensitive area. μm; the pseudo-equivalent heavy ion LET range is 10–150 MeV·cm² / mg, and the energy required to generate an electron-hole pair in GaN. eV, track radius nm is calculated using SRIM software.

[0037] Before reaching the GaN channel layer, the 355nm laser must pass through 0.6μm of silicon dioxide. 0.1μm silicon nitride The complex refractive index and absorption coefficient of each layer at this wavelength are shown in Table 1, along with the 10nm AlGaN barrier layer.

[0038] Table 1: Complex refractive index and absorption coefficient of multilayer structures in GaN HEMT devices ( =355nm) Under perpendicular incidence conditions, the intensity reflectivity and transmittance of the interface between two adjacent media are given by the Fresnel formula; neglecting multiple reflections between the interfaces and calculating the absorption of each layer according to the Beer-Lamber law, the reflectivity, transmittance and actual absorption power of each layer are obtained in turn, as shown in Tables 2 and 3 respectively.

[0039] Table 2: Approximate reflectance and transmittance of each interface during a single incident event Table 3: Actual absorbed power and emitted power of each layer (normalized to 1W peak incident power) As shown in Table 3, the peak light intensity actually entering the gallium nitride layer is approximately 0.74 times the incident light intensity, which is the total transmittance of the multilayer structure. The incident light intensity is multiplied by this coefficient in subsequent calculations. The laser-induced peak carrier concentration is then calculated based on this coefficient.

[0040] Pulse peak power W; On-axis incident peak intensity W / m²; Peak light intensity entering the GaN layer W / m².

[0041] Since gallium nitride has strong absorption at 355 nm, and the absorption depth is only about 67.7 nm, the divergence of the Gaussian beam within this depth is negligible, therefore we take... At peak position , At that point, the absorbed power density W / m³, pulse absorbed energy density J / m³, the corresponding peak photogenerated carrier concentration is approximately cm - ³.

[0042] This leads to the establishment of a mapping between peak concentration and LET. mg / cm³, eV and nm And take the same unit, and get cm - ³, where LET is measured in MeV·cm² / mg. Let ,Right now The equivalent LET is approximately 33.5 MeV·cm² / mg, which falls within the tens of MeV·cm² / mg range commonly used in heavy ion single-particle burn-off tests. This is within the LET range of typical heavy ions such as gold and tantalum, and is physically reasonable.

[0043] Finally, corrections for space constraint factor and charge collection efficiency are taken into account. In this embodiment, the lateral radius of the sensitive region... μm, laser spot μm, most charge carriers fall within the sensitive region, spatial constraint factor Furthermore, considering recombination and electric field distribution in gallium nitride, the charge collection efficiency is taken. Therefore, the corrected effective peak concentration cm - ³, correspondingly lowering the equivalent LET to approximately 19.5 MeV·cm² / mg. This result agrees well with the typical single-particle burn-out threshold (LET) of gallium nitride-based high electron mobility transistors, which is approximately tens of MeV·cm² / mg, validating the rationality of the modified model; in actual tests, the corresponding critical laser energy is typically in the hundreds of picojoules range.

[0044] Example 2 To further verify the peak concentration equivalence criterion proposed in this invention, this embodiment uses semiconductor device simulation software, such as Silvaco Atlas, to perform two-dimensional numerical simulations of gallium nitride-based high electron mobility transistors for aerospace power supplies. The simulations simulate carrier generation and transport processes under heavy ion irradiation and 355nm ultraviolet pulsed laser irradiation, respectively. The simulation modeling structure is as follows: Figure 3 As shown.

[0045] The constructed device structure is consistent with that of Example 1: the lateral coordinate range is -2 to 18 μm, the source is located at -2 to -1 μm, the gate at 1 to 2 μm, the drain at 17 to 18 μm, and the field plate at -1 to 4 μm; the longitudinal direction extends from the bottom of the substrate at -0.81 μm to the GaN buffer layer at 2.05 μm, the aluminum gallium nitride barrier layer is located at 0 to 0.015 μm (Al composition 0.20), the GaN channel and buffer layer are located at 0.015 to 2.05 μm, and the p-type GaN gate region is located at 1 to 2 μm laterally and -0.11 to 0 μm longitudinally, with a p-type doping concentration of approximately cm - ³. The mesh is refined at the heterojunction interface and the gate region edges.

[0046] The physical models include Shockley-Reid-Hall SRH recombination, Auger recombination, Fermi statistics, temperature-dependent mobility, low-field mobility models, polarization models including spontaneous and piezoelectric polarization, and buffer layers with energy levels of approximately 0.36 eV and concentrations of approximately [missing information]. cm - The acceptor-type electron trap of ³ uses the Selberherr model applicable to GaN for collisional ionization.

[0047] Heavy ion irradiation was set to vertical incidence, with the incident start point at (4μm, -0.81μm) and the ending point at (4μm, 2.05μm), and the track radius at 0.05μm. The LET value was set by the charge linear density parameter, which in this embodiment was set to 0.8pC / μm and can be converted into the corresponding LET value. The time distribution of carrier generation rate was set to Gaussian pulses, with a peak time of about 4ps and a characteristic time of about 2ps.

[0048] During transient solution, the drain voltage is first scanned to approximately 520V and the steady-state structure is saved. Then, a single-event event is applied, and the calculation is performed stepwise from approximately 1 ps to approximately 1 ms. The structure file is saved at typical times such as 4 ps, 10 ps, ​​1 ns, 10 ns, 1 μs, and 1 ms. The peak concentration is obtained by extracting the carrier concentration distribution along the track centerline, i.e., at a lateral coordinate of 4 μm. Simulation results of electron concentration distribution within the device after heavy ion irradiation are as follows: Figure 4 As shown.

[0049] Subsequently, using the same device structure, a 355nm laser was defined in beam statements: wavelength 0.355μm, spot center located at (4μm, -0.81μm), perpendicular incidence, transverse intensity with Gaussian distribution, standard deviation of approximately 0.3536μm, corresponding to a waist radius of approximately 0.5μm. The complex refractive index at this wavelength was set using material statements, with GaN real part 2.575 and imaginary part 0.417 and AlGaN real part 2.534 and imaginary part 0.279, to account for reflection and transmission at the multilayer film interface.

[0050] The time waveform of the laser pulse is achieved using a linear ramp combination, with a rise time of approximately 10 ps, ​​a peak hold of approximately 877 ps, and a fall time of approximately 10 ps, ​​for a total pulse width of approximately 897 ps. The generation rate parameter corresponding to the peak intensity is set to 1e4. The transient solution is divided into a pulse action phase and a relaxation phase, approximately 2 ns, 10 ns, 100 ns, and 1 μs, respectively. The structure is preserved and the transient current of the electrodes is recorded. The peak concentration is obtained by extracting the carrier concentration distribution along the depth direction at the center of the laser spot. Simulation results of electron concentration distribution within the device after ultraviolet pulsed laser irradiation are as follows: Figure 5 As shown.

[0051] Laser simulation results The results obtained from heavy ion simulation A comparison was performed. When the deviation between the two exceeded a set range, such as 10%, the peak concentrations were made equal by adjusting the heavy ion track radius, for example, from 0.05 μm to 0.04 μm, or by adjusting the Gaussian standard deviation in the laser beam statement to change the focused spot size. The calibrated parameters are then used to establish a precise mapping between laser energy and heavy ion LET. Simulation results show that the peak carrier concentration formed near the center of the laser spot by laser irradiation is on the same order of magnitude as the peak carrier concentration formed by heavy ions at the center of the track, and a good match can be achieved after fine-tuning the above parameters. This verifies the rationality of using equal peak concentration as an equivalence criterion at the device physics level.

[0052] Example 3 This embodiment presents a theoretical simulation system for pulsed laser equivalent heavy-ion irradiation to implement the above method. It includes a parameter input module, a laser carrier distribution calculation module, a heavy-ion carrier distribution calculation module, an equivalent mapping module, a simulation verification module, and a calibration module. The parameter input module is used to input laser parameters, material parameters, and device parameters. Laser parameters include wavelength, pulse energy, pulse width, and focused beam waist radius. Material parameters include the real part of the complex refractive index, the extinction coefficient (obtainable by ellipsometer measurement), the single-photon absorption coefficient determined by the extinction coefficient, the two-photon absorption coefficient, the energy required to generate one electron-hole pair, and the material density. Device parameters include surface reflectivity, multilayer thin film transmission coefficient, the transverse radius of the sensitive region, and the charge collection efficiency. The laser carrier distribution calculation module, based on the input parameters, uses a Gaussian beam propagation model and the Beer-Lambert absorption law. It first obtains the initial light intensity distribution entering the gallium nitride layer through multilayer dielectric transmission, then calculates the absorption attenuation along the depth direction to obtain the three-dimensional light intensity distribution, and finally converts it into a photogenerated carrier concentration distribution and takes the maximum value. It can optionally incorporate single-photon or two-photon absorption mechanisms, as well as corrections for spatial confinement factor and charge collection efficiency. The heavy-ion carrier distribution calculation module first calculates the linear carrier density per unit length based on the LET value, material density, electron-hole pair generation energy, and track radius. Then, under the assumptions of uniform or Gaussian distribution, it obtains the peak concentration at the track center. The equivalent mapping module uses the equality of peak carrier concentration as a criterion to inversely deduce the equivalent LET for a given laser parameter, or to calculate the required laser energy for a given LET, and integrates spatial constraint factor and charge collection efficiency correction. When the laser energy approaches the single-particle burn-out threshold of the device, this module automatically replaces the total carrier number equivalence criterion with the peak concentration equivalence criterion, outputting a two-stage equivalent specification that takes into account both weak and strong fields. The simulation verification module, namely the TCAD simulation verification module, performs two-dimensional or three-dimensional numerical simulation verification and parameter optimization on the equivalent mapping results. The calibration module uses at least two types of heavy ions with different LET values ​​to perform multi-point calibration on the equivalent mapping results, establishing a piecewise mapping function between pulsed laser energy and heavy ion LET values.

[0053] The aforementioned quantitative estimation system can be embedded into a computer control system in software form, and in actual testing, it can be combined with hardware such as a pulsed laser with adjustable wavelength, energy and pulse width, a beam shaping and focusing module with microscope objectives and camera, a precision three-dimensional moving stage, a probe station with a T-type bias, a power supply and a high-frequency oscilloscope to form a complete single-event effect laser simulation test system, thereby realizing the estimation, verification and correction of the equivalent LET.

[0054] This embodiment further provides a threshold calibration procedure to determine and calibrate the single-event burn-out threshold (LET) of the device.

[0055] 1) Use a heavy ion accelerator to perform single-event burn-out threshold tests on gallium nitride-based high electron mobility transistor devices under given bias conditions, and record the critical LET value that causes the device to burn out. 2) Irradiate the same device with a pulsed laser under the same bias conditions, gradually increase the laser energy until the device burns out due to a single particle, and record the critical laser energy; 3) Applying the peak concentration equivalent model of this invention, the critical laser energy is converted into the corresponding equivalent LET threshold; 4) Compare the LET threshold obtained by laser equivalent with the LET threshold measured by the heavy ion accelerator. When the deviation between the two exceeds the set range, such as 20%, adjust the model parameters, including the heavy ion track radius and the laser focusing spot size (where the laser focusing spot size can be measured and calibrated by the knife-edge method), until the deviation converges, thereby obtaining a high-precision equivalent mapping relationship.

[0056] Building upon this foundation, this embodiment further employs heavy ions with different LET values, such as carbon, neon, argon, krypton, and xenon, for multi-point testing and calibration. The measured thresholds of each ion are mapped point-by-point to the equivalent laser thresholds, and a piecewise mapping function between laser energy and heavy ion LET is established. This ensures the estimation system provides accurate equivalent results across a wide LET range. Therefore, after completing one offline calibration, the single-particle burn-off resistance of devices of the same model can be quickly predicted solely based on the critical energy measured by the pulsed laser, eliminating the need for repeated heavy ion accelerator use. This significantly improves testing efficiency, reduces experimental costs, and can guide the radiation hardening design of devices.

[0057] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; only preferred embodiments of the present invention are illustrated. The descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. As long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0058] It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A theoretical simulation method for pulsed laser equivalent heavy ion irradiation, characterized in that, Includes the following steps: Step S1: Determine the parameters of the GaN HEMT device and the laser parameters. The parameters of the GaN HEMT device include the layered structure of the GaNHEMT device, the material and doping of each layer, and the laser parameters include the laser wavelength, pulse energy, pulse width and focused spot waist radius. Step S2: Establish the three-dimensional spatial distribution of non-equilibrium carriers generated by pulsed laser within the semiconductor material of the GaN HEMT device, and calculate the laser-induced peak carrier concentration based on the laser parameters and the optical properties of the semiconductor material; Step S3: Establish a columnar distribution of non-equilibrium carriers generated by heavy ions along the track in the semiconductor material, and calculate the peak carrier concentration induced by heavy ions based on the linear energy transfer (LET) value of heavy ions and the characteristics of the semiconductor material. Step S4: Using the laser-induced peak carrier concentration being equal to the heavy ion-induced peak carrier concentration as an equivalence criterion, establish a mapping relationship between the pulse energy of the pulsed laser and the linear energy transfer value of the heavy ions, and based on the mapping relationship, deduce the equivalent linear energy transfer value from the given pulse energy, or deduce the required pulse energy from the given linear energy transfer value.

2. The method according to claim 1, characterized in that, The calculation of the laser-induced peak carrier concentration includes: based on the laser parameters and the complex refractive index and absorption coefficient of each layer of the GaN HEMT device, considering the interfacial transmission of the multilayer heterostructure and the propagation of the Gaussian beam within the medium, calculating the pulse peak power. On-axis incident peak light intensity Incident light intensity entering semiconductor materials ,depth Waist radius at the point Light intensity distribution inside semiconductor materials Absorbed power density Pulse absorbed energy density and photogenerated carrier concentration : ； ； ； ； ； ； ； ； and take The maximum value is taken as the laser-induced peak carrier concentration. ; Rayleigh length Single photon energy , For pulse energy, The pulse width. To focus the beam's waist radius, The total transmittance of the multilayer heterostructure is . Let be the real part of the complex refractive index of the semiconductor material. The single-photon absorption coefficient is... The wavelength of the laser. Let be Planck's constant. The speed of light in a vacuum Radial coordinates, These are depth coordinates.

3. The method according to claim 1, characterized in that, The calculation of the heavy ion-induced peak carrier concentration includes: calculating the linear carrier density per unit length based on the linear energy transfer value of heavy ions, material density, and the average energy required to generate one electron-hole pair. : ； Then, combining the heavy ion track radius, and assuming a uniform or Gaussian carrier distribution within the track, the peak carrier concentration at the track center is calculated. : ； in For material density, The linear energy transfer value for heavy ions. The average energy required to generate an electron-hole pair denoted as the heavy ion track radius.

4. The method according to claim 1, characterized in that, The laser-induced carrier distribution calculation is based on the single-photon absorption and two-photon absorption involved in the laser absorption process: Introducing single-photon absorption coefficient With two-photon absorption coefficient ; For the case where single-photon absorption is dominant, the light intensity along the depth satisfies Photogenerated carrier generation rate ; For cases where two-photon absorption is not negligible, numerical solutions to the coupling equations are required. and And perform spatiotemporal integration by combining the pulse time waveform; in For light intensity, For single photon energy, Photogenerated carrier concentration, Photogenerated carrier generation rate For depth coordinates, For time.

5. The method according to claim 1, characterized in that, The method further includes correcting the laser-induced peak carrier concentration by introducing a space constraint factor and a charge collection efficiency. The space constraint factor characterizes the proportion of carriers falling within the sensitive region of the device, and the charge collection efficiency characterizes the proportion of charge effectively collected by the electrodes. The corrected peak carrier concentration is... Among them, spatial constraint factor , The peak carrier concentration induced by laser. This is the corrected peak carrier concentration. The horizontal radius of the sensitive area. To focus the beam's waist radius, For charge collection efficiency; The modified peak carrier concentration is used in solving the equivalent criterion.

6. The method according to claim 1, characterized in that, The method also includes using semiconductor simulation software to establish a structural mesh and physical model for the GaN HEMT device, wherein the physical model includes a carrier recombination model, a mobility model, a polarization effect model, and a trap model. Ultraviolet pulsed laser irradiation and heavy ion irradiation were applied respectively to extract the carrier concentration distribution and electrical characteristics near the surface of the device. The simulated peak carrier concentration was compared with the calculated peak carrier concentration. By adjusting the model parameters, the deviation between the simulation results and the calculated results was made to fall within a set range, thereby verifying the mapping relationship and calibrating the parameters.

7. The method according to any one of claims 1 to 6, characterized in that, The method is applied to the evaluation of single-event effects in GaN power devices for aerospace applications. By irradiating the device under test with ultraviolet pulsed laser, the pulsed laser energy is measured when the device under test experiences a single-event transient or single-event burn-up. The equivalent criterion of peak carrier concentration is used to calculate the heavy-ion linear energy transfer threshold corresponding to the pulsed laser energy, and the single-event resistance capability of the device under test is predicted before heavy-ion accelerator experiments.

8. The method according to claim 7, characterized in that, The method further includes a model verification step: comparing the heavy ion linear energy transfer threshold obtained by laser equivalent with the linear energy transfer threshold measured on the same device on a heavy ion accelerator; when the deviation between the two exceeds a set range, adjusting the model parameters until the deviation converges; and using at least two heavy ions with different linear energy transfer values, establishing a piecewise mapping function between pulsed laser energy and heavy ion linear energy transfer value.

9. A theoretical simulation system for pulsed laser equivalent heavy ion irradiation, characterized in that, include: The parameter input module is used to input laser parameters, material parameters, and device parameters; The laser carrier distribution calculation module is used to calculate the three-dimensional spatial distribution and peak carrier concentration of non-equilibrium carriers generated by pulsed laser in semiconductor material based on the parameters input by the parameter input module. The heavy ion carrier distribution calculation module is used to calculate the columnar distribution of carriers generated by heavy ions along the track and its peak carrier concentration based on the linear energy transfer value of heavy ions and the material parameters. The equivalent mapping module is used to calculate and output the equivalent linear energy transfer value corresponding to the pulse energy, or the equivalent pulse energy corresponding to the linear energy transfer value, based on the criterion that the peak carrier concentration induced by the laser is equal to the peak carrier concentration induced by heavy ions. The simulation verification module is used to perform numerical simulation verification and parameter optimization on the results obtained by the equivalent mapping module.

10. The system according to claim 9, characterized in that, The system also includes a calibration module, which is used to perform multi-point calibration on the equivalence relationship output by the equivalence mapping module using at least two heavy ions with different linear energy transfer values, and to establish a piecewise mapping function between pulsed laser energy and heavy ion linear energy transfer value.

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