Bias effects on the electro-optic response of Ge-on-Si waveguide photodetectors

Silicon photonics, allowing for the integration of optoelectronic components into CMOS-compatible platforms, has shown great promise in the development of next-generation telecommunication systems and fast, low-power data interconnects. Within this framework, the increasing transistor integration and power dissipation density has led, during the last decades, to a steady decrease of the CMOS bias voltages. This trend may also affect the operation of silicon photonics components: the present work is focused on the effects of lower bias in Ge-on-Si waveguide photodetectors (WPDs), using the electro-optic (EO) frequency response as a figure of merit

Modeling the electronic transport in FinFET-like lateral Ge-on-Si pin waveguide photodetectors for ultra-wide bandwidth applications

We determined the velocities of photogenerated electrons and holes in FinFET-like lateral Ge-on-Si waveguide photodetectors with Monte Carlo transport simulation. The calculated carrier velocities were used in a 3D multiphysics model focused on the investigation of the electro-optic frequency response. The good match between the bandwidths predicted by the model and the corresponding experimental values available from the literature, larger than 200 GHz, indicates the importance of moving beyond conventional drift-diffusion models for a realistic description of next-generation high-speed integrated photodetectors

3D multiphysics transient modeling of vertical Ge-on-Si pin waveguide photodetectors

We report transient simulations of Ge-on-Si vertical pin waveguide photodetectors (WPDs), where the optical generation term used by the time-domain model is the FDTD solution of the electromagnetic problem treated as a spatially-distributed pulsed signal. This approach, validated against experimental measurements of the frequency response, paves the way to future studies of the dynamic response of WPDs, enabling the description of complex modulation schemes including saturation effects and current tails due to slow carriers

Next-generation long-wavelength infrared detector arrays: competing technologies and modeling challenges

In this paper, Sb-based superlattice fabrication processing is based on standard III-V technology, implying lower costs of mass production and constituting a relatively new alternative for an IR material system in LWIR and VLWIR bands

Modeling the frequency response of vertical and lateral Ge-on-Si waveguide photodetectors: Is 3D simulation unavoidable?

Using a 3D multiphysics model as a reference, we investigate the achievements and limitations of a simpler 2D drift-diffusion model to reproduce and optimize the electrooptical frequency response of vertical and lateral Ge-on-Si waveguide photodetectors

Impact of Fabrication Variabilities on Performance of Avalanche Photodetectors

Avalanche 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

Ge-on-Si waveguide photodetectors: multiphysics modeling and experimental validation

This work compares a multiphysics modeling approach with experimental measurements of two Ge-on-Si butt-coupled waveguide photodetectors. The coupled three-dimensional electromagnetic and electrical simulation of the frequency response shows promising agreement with the measurements at 1310 nm, and provides detailed information about significant microscopic quantities, such as the spatial distribution of the optical generation rate

Modeling the effects of graded and abrupt mole fraction profiles in pBn and nBn HgCdTe barrier detectors

We 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

Optical Power Screening Effects in Ge-on-Si Vertical Pin Photodetectors

We present an experimental and numerical study on the effects of the input optical power on the electro-optic frequency response of a Ge-on-Si vertical pin waveguide photodetector. Experimental results were provided by Cisco Systems, which characterized several nominally identical devices. Increasing the optical power from −2 dBm to 3 dBm, a significant decrease of the electro-optic frequency response was observed in the O-band, from about 40GHz down to approximately 32GHz. This trend is accurately predicted by our 3D multiphysics model, where Maxwell’s equations are solved with the FDTD method to evaluate the spatial distribution of photogenerated carriers, which is then converted in an optical generation rate included in the drift-diffusion solver. The 3D model provides a detailed explanation of the experiments by showing the effects of carrier screening on the magnitude of the electric field profile, which is reduced for high optical power, slowing the photogenerated carriers and reducing the bandwidth

Exploring Optimal Dark Current Design in HgCdTe Infrared Barrier Detectors: A TCAD and Semianalytic Investigation

The dark current is a fundamental figure of merit to characterize the performance of high-sensitivity, low-noise mid- and far-infrared barrier photodetectors. In the context of HgCdTe barrier photodetectors, the trend is to use very low doping concentrations, in an attempt to minimize recombination processes. In the present work, through TCAD simulations, we delve deeper into the design of low-dark-current $p{\mathrm{B}}n$ detectors, showing the possible existence of an optimum doping. This occurrence is investigated and interpreted also by means of closed-form expressions for the lifetimes, emphasizing the role of the interplay between Auger and Shockley-Read-Hall generation processes