Epitaxial low temperature grown GaAs (LT-GaAs) on silicon (LT-GaAs/Si) has the potential for terahertz (THz) photoconductive antenna applications. However, crystalline, optical and electrical properties of heteroepitaxial grown LT-GaAs/Si can be very different from those grown on semi-insulating GaAs substrates (reference). In this study, we investigate optical properties of an epitaxial grown LT-GaAs/Si sample, compared to a reference grown under the same substrate temperature, and with the same layer thickness. Anti-phase domains and some crystal misorientation are present in the LT-GaAs/Si. From coherent phonon spectroscopy, the intrinsic carrier densities are estimated to be ~1015 cm−3 for either sample. Strong plasmon damping is also observed. Carrier dynamics, measured by time-resolved THz spectroscopy at high excitation fluence, reveals markedly different responses between samples. Below saturation, both samples exhibit the desired fast response. Under optical fluences ≥ 54 μ J/cm2, the reference LT-GaAs layer shows saturation of electron trapping states leading to non-exponential behavior, but the LT-GaAs/Si maintains a double exponential decay. The difference is attributed to the formation of As-As and Ga-Ga bonds during the heteroepitaxial growth of LT-GaAs/Si, effectively leading to a much lower density of As-related electron traps.
@article{arxiv.2107.09231,
title = {Effect of heteroepitaxial growth on LT-GaAs: ultrafast optical properties},
author = {Jessica Afalla and Elizabeth Ann Prieto and Horace Andrew Husay and Karl Cedric Gonzales and Gerald Catindig and Aizitiaili Abulikemu and Armando Somintac and Arnel Salvador and Elmer Estacio and Masahiko Tani and Muneaki Hase},
journal= {arXiv preprint arXiv:2107.09231},
year = {2021}
}