Strain-induced InGaAs/InAlAs superlattices for terahertz radiation

TL;DR

This paper investigates how residual strain in InGaAs/InAlAs superlattices affects ultrafast photocarrier dynamics, demonstrating a novel design that achieves ultrashort relaxation times and enhanced terahertz emission for advanced THz applications.

Contribution

The study introduces a new strained InGaAs/InAlAs superlattice design that significantly reduces photocarrier relaxation time without doping, enhancing THz emission capabilities.

Findings

Ultrashort photocarrier relaxation time of ~1.5 ps achieved

Increased THz emission amplitude with residual strain

Strain influences defect trapping and interface scattering

Abstract

We study the influence of residual strain in InGaAs/InAlAs superlattice (SL) on the ultrafast photocarrier dynamics under femtosecond laser excitation. We propose and fabricate a novel-designed strained InGaAs/InAlAs SL which allows us to obtain an ultrashort photocarrier relaxation time of $\tau\sim$ 1.5 ps without Be-doping of the InGaAs photoconductor. We assume two dominant mechanisms to be responsible for a sharp reduction of $\tau$: photocarriers trapping by defect levels in InAlAs barriers and increased photocarriers scattering at InGaAs/InAlAs interface roughness due to residual strain in the SL. The THz time-domain spectroscopic measurements reveal an increase in both emitted THz waveform and spectrum amplitudes with an increase of residual strain in SL. The results might be of considerable interest for accommodating the needs of THz pulsed spectroscopy and imaging in fundamental and applied branches of THz science and technology.