Material configurations for n-type silicon-based terahertz quantum cascade lasers

TL;DR

This study compares different silicon-based heterostructures for terahertz quantum cascade lasers, finding that (001) Ge/GeSi configurations offer the best simulated performance for 3 and 4 THz emissions.

Contribution

It systematically evaluates three proposed material configurations for silicon-based THz QCLs using optimization and simulation techniques.

Findings

(001) Ge/GeSi structures outperform others in simulated performance.

Optimal configurations vary with emission frequency.

Simulation results guide material choice for better QCL performance.

Abstract

Silicon-based quantum cascade lasers (QCLs) offer the prospect of integrating coherent THz radiation sources with silicon microelectronics. Theoretical studies have proposed a variety of n-type SiGe-based heterostructures as design candidates, however the optimal material configuration remains unclear. In this work, an optimization algorithm is used to design equivalent THz QCLs in three recently-proposed configurations [(001) Ge/GeSi, (001) Si/SiGe and (111) Si/SiGe], with emission frequencies of 3 and 4 THz. A systematic comparison of the electronic and optical properties is presented. A semi-classical electron transport simulation is used to model the charge carrier dynamics and calculate the peak gain, the corresponding current density and the maximum operating temperature. It is shown that (001) Ge/GeSi structures yield the best simulated performance at both emission frequencies.