RASER: Semiconductor Detector Simulation

• RASER is a simulation framework for semiconductor detectors that integrates electric field modeling, carrier transport, and radiation-induced defect physics.
• It couples multiple tools such as Geant4, FEniCS, DEVSIM, and ROOT to simulate timing response and signal induction based on the Shockley–Ramo theorem.
• Its applications span from 4H-SiC LGADs and silicon strip detectors to CEPC luminosity monitors, achieving time resolutions as low as 25 ps and over 90% charge collection efficiency.

RAdiation SEmiconductoR (RASER) is a semiconductor-detector simulation framework used to model electric fields, carrier transport, induced current, timing response, and, in later work, irradiation-induced defect physics in silicon and 4H-SiC devices. In the cited literature, RASER develops from a fast timing-simulation program for planar and 3D 4H-SiC detectors into a broader workflow that couples device-level electrostatics and defect modeling with Geant4 energy deposition and Shockley–Ramo signal induction. Its reported applications include 4H-SiC PIN detectors, 4H-SiC low gain avalanche detectors (LGADs), irradiated silicon strip detectors, proton-damaged 4H-SiC PIN devices, and CEPC luminosity-monitor optimization (Tan et al., 2021, Wang et al., 2023, Li et al., 29 Apr 2025, Li et al., 12 Mar 2025, Li et al., 31 Jul 2025).

1. Development and scope

RASER appears in the cited detector literature as a self-developed, open-source simulation environment oriented toward semiconductor detector physics rather than a single-purpose numerical kernel. The published record shows a clear sequence: timing-oriented 4H-SiC studies first, then electrical-and-timing co-simulation for SiC LGADs, followed by explicit radiation-damage modeling for silicon and SiC, and finally system-level collider instrumentation studies.

Paper	Reported role of RASER	Representative result
"Timing performance simulation for 3D 4H-SiC detector" (Tan et al., 2021)	Fast simulation program for planar and 3D 4H-SiC detector timing	3D-4H-SiC-5E estimated at 25 ps
"Design and simulation of a novel 4H-SiC LGAD timing device" (Wang et al., 2023)	Electrical and timing simulation of 4H-SiC LGADs	$(35.0 \pm 0.2)$ ps at $-800$ V
"Mechanisms of proton irradiation-induced defects on the electrical performance of 4H-SiC PIN detectors" (Li et al., 12 Mar 2025)	TCAD-based Deep-Level Compensation Model in RASER	Leakage current decreases and C–V becomes nearly flat up to $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$
"Simulation of radiation damage effect on silicon detectors using RASER" (Li et al., 29 Apr 2025)	Irradiated silicon-detector framework combining DEVSIM, Geant4, transport, and Shockley–Ramo signal induction	CEPC-like inner tracker predicted to maintain over 90% CCE
"Preliminary design and simulation for CEPC fast luminosity monitor detector based on 4H-SiC" (Li et al., 31 Jul 2025)	Detector-response and geometry-optimization tool for collider luminosity feedback	$2\%$ relative precision at 1 kHz

This progression suggests an expansion from device-level timing studies toward end-to-end irradiated-detector and beam-instrumentation workflows. The emphasis remains on detector observables rather than on general-purpose semiconductor process simulation.

2. Architecture and computational methodology

RASER is described as a combined workflow rather than a monolithic solver. In the electrical and irradiation papers, DEVSIM provides device-level electrostatics and transport-related quantities; in the timing studies, FEniCS is used for electric-field and weighting-potential calculation; Geant4 supplies microscopic energy deposition; and the RASER transport-and-signal stage computes induced current, collected charge, and timing observables. ROOT is also part of the timing stack in the SiC LGAD work (Wang et al., 2023, Tan et al., 2021, Li et al., 29 Apr 2025, Li et al., 12 Mar 2025).

The signal stage is based on the Shockley–Ramo theorem. In the silicon irradiation workflow, the induced current is written as

$i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$

and collected charge as

$Q=\int i(t)\,dt.$

For timing studies, RASER combines this induced-current calculation with a simplified current amplifier, measured electronics noise, and constant fraction discrimination. The LGAD paper decomposes timing resolution as

$$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$

In the 3D SiC timing paper, the reported working approximation is

$$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$

For irradiated-device studies, the framework is explicitly drift-diffusion based. The 4H-SiC proton-damage paper states the Poisson and continuity equations in the forms

$\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$

$\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$

with

$-800$0

The same paper incorporates field-enhanced SRH generation through a Hurkx-style correction, while the silicon-strip irradiation paper adds SRH recombination, effective space charge distribution, trapping-time calculation, van Overstraeten impact ionization, and trap-assisted tunneling (Li et al., 12 Mar 2025, Li et al., 29 Apr 2025).

3. Timing-detector studies in 4H-SiC

The earliest RASER application in the cited literature concerns timing performance in planar and 3D 4H-SiC detectors. The validation device was a planar detector designed by Nanjing University with $-800$1 area, $-800$2 active epitaxial layer, and $-800$3 substrate. Under the reported $-800$4 beta-source setup, the simulated time resolution was $-800$5 ps, compared with a measured $-800$6 ps, which the authors used as the software-validation benchmark (Tan et al., 2021).

The same study then examined 3D 4H-SiC geometries. A baseline 3D detector of $-800$7 area and $-800$8 thickness used an effective n-type substrate concentration of $-800$9, column radius $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$0, and column spacing $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$1. At $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$2 V, the reported performance comparison was: planar detector rise time $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$3 ns, pulse height $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$4 mV, time resolution $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$5 ps; 3D-4H-SiC-7E rise time $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$6 ns, pulse height $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$7 mV, time resolution $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$8 ps; and 3D-4H-SiC-5E rise time $7.8\times10^{14}\ n_{eq}/\mathrm{cm}^2$9 ns, pulse height $2\%$0 mV, time resolution $2\%$1 ps. The five-electrode design was favored because it combined simpler fabrication with better timing and larger pulse height (Tan et al., 2021).

These results were interpreted in terms of 4H-SiC material transport and 3D geometry. The paper reports a saturated electron velocity of $2\%$2 at $2\%$3 K, with simulated drift velocities around $2\%$4 of $2\%$5 for electrons and $2\%$6 for holes. Because the 3D structure decouples thickness from inter-electrode distance, thickness can raise signal charge without imposing the planar timing penalty associated with long drift paths. The same study reports that time resolution improves with higher bias voltage until velocity saturation is approached, improves with increasing thickness, and degrades with increasing column spacing (Tan et al., 2021).

RASER was later used for a full-epitaxial-growth 4H-SiC LGAD with stack

$2\%$7

The reported electrical results were gain-layer depletion around $2\%$8 V, full depletion around $2\%$9 V, and breakdown around $i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$0 V, implying a working-voltage range of about $i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$1 V to $i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$2 V. Timing simulations for 50,000 beta-detection events yielded a time resolution of $i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$3 ps at $i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$4 V, better than the previously reported 4H-SiC PIN detector and stated to be basically the same as a Si-based LGAD value of $i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$5 ps. The paper also states that the working voltage and gain effectiveness were verified by electrical-performance simulation (Wang et al., 2023).

4. Radiation-damage modeling in silicon and SiC

RASER’s most explicit radiation-damage extension appears in the silicon-strip framework built for leakage current and charge collection efficiency after irradiation. That workflow uses DEVSIM for irradiated electrostatics and defect-enabled transport, Geant4 for particle passage and energy deposition, carrier drift in the irradiated field with trapping, and signal induction via the Shockley–Ramo theorem. The defect model is the Hamburg penta trap model (HPTM), but with introduction rates modified to match ATLAS ITk strip-sensor IV and CCE data (Li et al., 29 Apr 2025).

HPTM defect	Type	Energy level
E30K	Donor	$i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$6
$i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$7	Acceptor	$i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$8
$i(t)=q\,\mathbf{v}(t)\cdot \mathbf{E}_w,$9	Acceptor	$Q=\int i(t)\,dt.$0
H220	Donor	$Q=\int i(t)\,dt.$1
$Q=\int i(t)\,dt.$2	Donor	$Q=\int i(t)\,dt.$3

The simulated sensor is a p-bulk strip detector with $Q=\int i(t)\,dt.$4 depth, $Q=\int i(t)\,dt.$5 doping concentration, $Q=\int i(t)\,dt.$6 strip pitch, $Q=\int i(t)\,dt.$7 electrode width, and simulation temperature $Q=\int i(t)\,dt.$8. Reported outputs include IV curves, electric-field distributions, trapping times, induced current waveforms, and CCE versus voltage and fluence. The framework reproduces the expected post-irradiation trends: strong leakage-current increase, increasingly obvious double-peak electric field at $Q=\int i(t)\,dt.$9 V, trapping times reaching the nanosecond scale near $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$0, lower-amplitude and longer-fall-time beta-source current pulses at $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$1 V, and good agreement with measured CCE at $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$2. For a CEPC-like inner tracker over ten years in Higgs mode at $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$3, the framework predicts over $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$4 charge collection efficiency (Li et al., 29 Apr 2025).

A distinct radiation-damage application concerns 80 MeV proton irradiation of 4H-SiC PIN detectors. That work combines DLTS, TRPL, and RASER-based TCAD to explain two reported features: reverse leakage current decreases with increasing proton fluence, and the C–V curve becomes flat or nearly constant-capacitance up to $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$5. The detector is a $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$6 4H-SiC PIN diode with a lightly doped n-type epitaxial region of approximately $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$7; the non-irradiated $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$8 device showed $$\sigma_t^2=\sigma^2_{TimeWalk}+\sigma^2_{Landau}+\sigma^2_{Distortion}+\sigma^2_{Jitter}+\sigma^2_{TDC}.$$9, depletion width $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$0, and full depletion around $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$1 V. DLTS identified $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$2 at $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$3 as the key irradiation-induced defect, and the RASER model used it as the single effective acceptor-like compensating center in a Deep-Level Compensation Model. TRPL gave minority-carrier lifetimes of $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$4 ns before irradiation, $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$5 ns at $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$6, and $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$7 ns at $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$8; the simulation accordingly used a pre-irradiation hole lifetime of $$\sigma_t^2 \approx \sigma_{tw}^2+\sigma_{\mathrm{jitter}}^2,\qquad \sigma_{\mathrm{jitter}}=\frac{t_p}{S/N}.$$9 ns, a tuned Hurkx parameter $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$0, and an effective intrinsic density $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$1. The stated interpretation is that compensation redistributes the electric field, lowers the maximum field, and thereby reduces field-enhanced SRH generation, so the leakage-current reduction is driven primarily by the electric-field change rather than by a simple defect-count argument (Li et al., 12 Mar 2025).

5. Collider-instrumentation and CEPC applications

RASER has also been used at the detector-system level for CEPC beam instrumentation. In the fast luminosity monitor study, the target operating context is CEPC Higgs mode at

$\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$2

with a requirement of $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$3 relative precision at 1 kHz for luminosity-driven dithering feedback. RASER was used to simulate primary radiative-Bhabha electrons hitting the beam pipe, the production of secondary showers, energy deposition in 4H-SiC pixels, induced current via the Shockley–Ramo theorem, threshold response, and sampled current aggregation (Li et al., 31 Jul 2025).

The preferred detector location is Position 1 at 10 m downstream of the interaction point. Two detector centers are placed at

$\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$4

Each detector is an array of $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$5 4H-SiC pixels with $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$6 thickness and active-region doping $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$7. After active-area and threshold scans, the optimized design consists of two detectors, one on each side of the beam pipe, each of size $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$8 and segmented into 12 pixels. With a per-channel threshold or noise level of $\nabla\cdot\Vec{E}=\frac{\rho}{\epsilon_s},$9, the design detects about $\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$0 primary electrons per ms, which satisfies the $\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$1 precision target at 1 kHz (Li et al., 31 Jul 2025).

A distinctive system observable introduced in that paper is the Total Sample Current (TSC),

$\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$2

namely the sum of sampled currents over both detectors, all pixels, and all sampling points in a 1 ms window. The paper reports a clear near-linear or linear correlation between TSC and luminosity attenuation. This suggests that, within the cited RASER literature, the framework is being used not only for detector-internal observables such as IV, C–V, electric field, and timing, but also for fast feedback quantities intended for machine operation (Li et al., 31 Jul 2025).

6. Terminological ambiguity and adjacent literatures

The acronym RASER is not unique. In magnetic-resonance literature it denotes “Radio-frequency Amplification by Stimulated Emission of Radiation,” including continuous PHIP-RASER at 14.1 T and 600.13 MHz, with $\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$3 self-emission for more than 10 minutes and linewidth about 2 ppb, and RASER MRI based on spontaneous imaging bursts that emerge without RF pulses from inverted spin ensembles (Pravdivtsev et al., 2019, Lehmkuhl et al., 2022). Those works concern resonator-coupled nuclear-spin emission rather than semiconductor detector simulation.

Several semiconductor-radiation-source papers are also adjacent in name or concept but are distinct from RAdiation SEmiconductoR. These include a theoretical proposal for stimulated terahertz emission in exciton-polariton semiconductor microcavities (Kavokin et al., 2010), helicity-controlled pulsed THz emission from the Rashba-type polar semiconductor BiTeBr via the circular photogalvanic effect (Kinoshita et al., 2018), Josephson radiation from an InSb nanowire junction (Woerkom et al., 2017), and THz rectification in semiconductor superlattices without electric-field domains (Isohätälä et al., 2012). Separate radiation-hard-semiconductor studies on SiC and GaN power devices, $\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$4-Ga$\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$5O$\frac{\partial n}{\partial t}=G_n-U_n+\frac{1}{q}\nabla\cdot\Vec{J_n},\qquad \frac{\partial p}{\partial t}=G_p-U_p+\frac{1}{q}\nabla\cdot\Vec{J_p},$6, and InAs/GaAs quantum-dot lasers likewise address material or device resilience rather than the RASER simulation framework (Fiore et al., 2013, Azarov et al., 2023, Li et al., 2024).

Accordingly, precise usage is necessary. In the detector literature summarized above, RASER denotes a semiconductor-device simulation framework centered on detector electrostatics, transport, induced-current formation, timing extraction, and, increasingly, irradiation-defect modeling. In magnetic-resonance and semiconductor-emitter literatures, the same or similar acronym refers to physically different phenomena.