Interband impact ionization and nonlinear absorption of terahertz radiations in semiconductor heterostructures

TL;DR

This paper presents a theoretical study of nonlinear terahertz absorption in InAs/AlSb heterostructures, highlighting the dominant role of impact ionization at high fields and explaining experimental observations.

Contribution

It introduces a comprehensive model considering multiple photon processes and impact ionization to explain nonlinear THz absorption in semiconductor heterostructures.

Findings

Impact ionization dominates high-field absorption.

Electron-disorder scattering influences low to intermediate fields.

The theory explains long-standing experimental results.

Abstract

We have theoretically investigated nonlinear free-carrier absorption of terahertz radiation in InAs/AlSb heterojunctions. By considering multiple photon process and conduction-valence interband impact ionization (II), we have determined the field and frequency dependent absorption rate. It is shown that (i) electron-disorder scatterings are important at low to intermediate field, and (ii) most importantly, the high field absorption is dominated by II processes. Our theory can satisfactorily explain a long standing experimental result on the nonlinear absorption in THz regime.