1,720,972 research outputs found
Ge-on-Si photodetectors for silicon photonics: multiphysics modeling and design
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Impact of Fabrication Variabilities on Performance of Avalanche Photodetectors
Full text linkAvalanche photodetectors (APDs) are a crucial technology for detection of weak optical signals. These devices operate on internal gain, meaning only the device currents, including the optical signal, are amplified [1] . This allows high performance APDs to maximize their signal-to-noise ratio as long as the excess noise due to the amplification process remains low. In this work, we investigate how slight geometric changes to a device design due to variabilities in the fabrication process can affect the performance of an APD. The performance metrics considered are gain, excess noise factor, and bandwidth
Small-Signal Compact Modeling and TCAD Validation of Ultra-Fast Lateral Ge-On-Si Waveguide Photodetectors
Full text linkWe present a compact small-signal equivalent circuit for ultra-fast lateral Ge-on-Si waveguide photodetectors, validated against full 3D drift-diffusion TCAD simulations. By evaluating the contributions of intrinsic and parasitic elements, the model enables prediction of device performance and offers direct insight into the RC limitations of the photodetector, useful in circuit level designs
Elliptically polarized light obtained from tilted high-contrast grating VCSELs
No full textWe show that ultrathin elliptically polarized VCSELs can be realized with standard high-contrast gratings (HCGs) whose bars are tilted to the semiconductor crystalline axes on the transverse plane, without relying on any 2D chiral layer. Revisiting orthogonal polarization suppression ratio (OPSR) measurements, we demonstrate that the reduced OPSR for tilted gratings is related to elliptical lasing polarization rather than degraded polarization selectivity. Simulations confirm that the polarization state can be tuned by balancing intrinsic and HCG-induced anisotropies. These devices provide integrated elliptically polarized and wavelength-tunable sources for chip-scale atomic devices
Effects of input optical power in lateral Ge-on-Si waveguide photodetectors: a 3D multiphysics modeling study
Full text linkWe present a three-dimensional (3D) multiphysics model that examines how increasing input optical power degrades the electro-optical frequency response performance of lateral Ge-on-Si waveguide photodetectors. Our approach combines finite-difference time-domain (FDTD) simulations and drift-diffusion modeling to capture both optical and electrical behaviors. Simulation results show that once the input power exceeds a few mW, the detector bandwidth is significantly reduced due to electric-field screening effects
Modeling self-heating in high-power non-circular VCSELs
Full text linkVCSEL applications are continuously growing, especially in sensing. High-power, i.e., large area, and single-mode are contradictory requirements, tackled by mastering VCSEL temperature distribution (TD) and proper design. We present here a viable approach aimed at efficiently introducing TD in 3D simulations of optical modes
TCAD Modeling and Simulation of Dark Current-Voltage Characteristics in High-Periodicity InGaN/GaN Multiple-Quantum-Wells (MQWs) Solar Cells
Full text linkGallium nitride (GaN) based high periodicity indium/GaN multiple quantum wells solar cells have recently been proposed for different applications: from operation in harsh environments, like space applications, to their use in concentrator solar harvesting system and wireless power transfer system. In this article, we extensively investigate the mechanisms, which influence the in-dark current-voltage characteristics of these device under no excitation by means of experimental measurements and numerical simulations performed with the technology computer-aided design (TCAD) Sentaurus suite from Synopsys. Two different nonlocal models are introduced: the first one considers intrabarrier tunneling, which was found to be the dominant conduction mechanism for voltages above the main diode turn-on; the second model considers trap-assisted tunneling, implemented through traps uniformly distributed in space and energy, to reproduce the current flow in the sub turn-on region. A good matching is obtained between the experimental and simulated electrical characteristics, by considering these nonlocal models in addition to the thermionic escape
Modeling Self-Heating in High-Power Single-Mode Phase-Coupled Linear VCSEL Arrays
Full text linkWe investigate the robustness of single-mode (SM) emission in high-power, large-area rectangular vertical-cavity surface-emitting lasers (VCSELs), emphasizing the impact of self-heating effects. Compablack to circular geometries, large-area rectangular VCSELs provide improved heat dissipation thanks to their high geometrical aspect ratio, and higher SM output power by means of their patterned reflectivity obtainable by an array of grating reliefs. Self-heating alters the refractive index of the device. We demonstrate, experimentally and numerically, how the related thermal lensing affects the transverse modes. By misaligning the antinodes of the promoted lasing mode and the surface reliefs, self-heating degrades SM operation if not properly accounted for in the relief position design. Combining thermal and optical models, we propose numerically optimized grating relief geometries ensuring robust SM emission across varying operating temperatures
Modeling the effects of graded and abrupt mole fraction profiles in pBn and nBn HgCdTe barrier detectors
Full text linkWe present a numerical simulation study at 200 K of pBn and nBn HgCdTe barrier detectors, focused on the effects of the composition profile on the J-V characteristics in dark. Considering a conventional barrier detector structure with three regions (absorber, barrier, cap), we discuss how the J-V characteristics are affected by the steepness of the cap/barrier and barrier/absorber interfaces, especially in the nBn configuration
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