Polarized photoreflectance and photoluminescence spectroscopy of InGaAs/GaAs quantum rods grown with As2 and As4 sources

Ramūnas Nedzinskas,Vytautas Karpus,Julius Kavaliauskas,Edmund H Linfield,Bronislovas Čechavičius,Lianhe Li,Gintaras Valušis,Suraj P Khanna

doi:10.1186/1556-276x-7-609

Abstract

We report photoreflectance (PR) and photoluminescence (PL) investigations of the electronic and polarization properties of different aspect ratio (height/diameter) InGaAs quantum rods (QRs) embedded in InGaAs quantum wells (QWs). These nanostructures were grown by molecular beam epitaxy using As2or As4sources. The impact of the As source on the spectral and polarization features of the QR- and QW-related interband transitions was investigated and explained in terms of the carrier confinement effects caused by variation of composition contrast between the QR material and the surrounding well. Polarized PR and PL measurements reveal that the polarization has a preferential direction along the crystal axis with a large optical anisotropy of about 60% in the (001) plane for high aspect ratio (4.1:1) InGaAs QRs. As a result, in PL spectra, the transverse magnetic mode dominated -cleaved surfaces (TM[001]>TE[110]), whereas the transverse electric mode prevailed for (110)-cleaved surfaces (). This strong optical anisotropy in the (001) plane is interpreted in terms of the hole wavefunction orientation along the direction for high aspect ratio QRs.

Highlights

Self-assembled semiconductor quantum dots (QDs) formed by molecular beam epitaxy (MBE) are the foremost candidates for numerous applications in optoelectronics
In addition to being able to engineer the transverse electric (TE) and transverse magnetic (TM) optical mode couplings, which is very beneficial for semiconductor optical amplifiers (SOAs), quantum rods (QRs) have a large intrinsic dipole moment, which opens up opportunities for their application in quantum memories and nonlinear electrooptic devices [3]
The PR spectrum splits into four principal sets of optical features, which correspond to specific optical transitions in the QR structures [7]

Summary

Introduction

Self-assembled semiconductor quantum dots (QDs) formed by molecular beam epitaxy (MBE) are the foremost candidates for numerous applications in optoelectronics (see e.g., [1]). Modifying the polarizationdependent optical gain function is, important for optoelectronic engineering. For this reason, columnar QDs or quantum rods (QRs) have been grown by MBE by depositing a short period InAs/GaAs superlattice (SL) on top of a seed QD layer [2]. Structural (TEM) analysis of such elongated nanostructures gives clear evidence of inplane shape anisotropy [2]. This is confirmed by very recent theoretical and experimental optical studies which demonstrate the presence of optical anisotropy in multilayer InAs/GaAs QD stacks [4]. It is clear that further work is required to elucidate the underlying mechanisms

Methods

Results

Conclusion