Effect of in-plane magnetic field on the photoluminescence spectrum of modulation-doped quantum wells and heterojunctions

TL;DR

This study investigates how an in-plane magnetic field affects the photoluminescence spectra of modulation-doped GaAs/AlGaAs quantum wells and heterojunctions, revealing field-induced spectral modifications linked to electron-hole separation.

Contribution

It provides a model explaining the spectral changes under magnetic field based on shifts in optical transition k-space, highlighting the role of electron-hole separation in PL modifications.

Findings

Magnetic field causes significant changes in PL spectra depending on electron-hole separation.

PL intensity of bulk excitons decreases with increasing magnetic field in heterojunctions.

The model qualitatively explains spectral modifications through shifts in conduction and valence subbands.

Abstract

The photoluminescence (PL) spectrum of modulation-doped GaAs/AlGaAs quantum wells (MDQW) and heterojunctions (HJ) is studied under a magnetic field ($B_{\|}$) applied parallel to the two-dimensional electron gas (2DEG) layer. The effect of $B_{\|}$ strongly depends on the electron-hole separation ($d_{eh}$), and we revealed remarkable $B_{\|}$-induced modifications of the PL spectra in both types of heterostructures. A model considering the direct optical transitions between the conduction and valence subband that are shifted in k-space under $B_{\|}$, accounts qualitatively for the observed spectral modifications. In the HJs, the PL intensity of the bulk excitons is strongly reduced relatively to that of the 2DEG with increasing $B_{\|}$. This means that the distance between the photoholes and the 2DEG decreases with increased $B_{\|}$, and that free holes are responsible for the hole-2DEG PL.