MOVPE-Grown Quantum Cascade Laser Structures Studied by Kelvin Probe Force Microscopy

Konstantin Ladutenko,Dmitry Revin,Vadim Evtikhiev,Andrey Krysa

doi:10.3390/cryst10020129

Konstantin Ladutenko, Dmitry Revin + Show 2 more

Open Access

https://doi.org/10.3390/cryst10020129

Copy DOI

Journal: Crystals	Publication Date: Feb 20, 2020
Citations: 1	License type: CC BY 4.0

Affiliation: Ioffe Institute, ITMO University, University of Sheffield

Abstract

A technique for direct study of the distribution of the applied voltage within a quantum cascade laser (QCL) has been developed. The detailed profile of the potential in the laser claddings and laser core region has been obtained by gradient scanning Kelvin probe force microscopy (KPFM) across the cleaved facets for two mid-infrared quantum cascade laser structures. An InGaAs/InAlAs quantum cascade device with InP claddings demonstrates a linear potential distribution across the laser core region with constant voltage drop across the doped claddings. By contrast, a GaAs/AlGaAs device with AlInP claddings has very uneven potential distribution with more than half of the voltage falling across the claddings and interfaces around the laser core, greatly increasing the overall voltage value necessary to achieve the lasing threshold. Thus, KPFM can be used to highlight design and fabrication flaws of QCLs.

Highlights

Metalorganic vapour phase epitaxy (MOVPE) of quantum cascade lasers (QCLs) [1,2] is a very demanding process
We present a technique for direct, high-spatial-resolution measurements of the voltage distribution across all the parts of QCL structures
The developed method can be very valuable for the optimization of and the observed (10.8 V) voltage at the threshold is minimal and depends on the slight variation in the QCL design as well as the epitaxial growth technology of QCLs

Summary

Introduction

Metalorganic vapour phase epitaxy (MOVPE) of quantum cascade lasers (QCLs) [1,2] is a very demanding process. The interface abruptness, intentional and unintentional doping, layer thicknesses, and material compositions may critically affect the performance of any conventional laser diodes. Various experimental techniques are used to assess the structural, electrical, optical and thermal properties of the as-grown material and fabricated devices, e.g., [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] in order to help to optimize the QCL design and related epitaxial growth technologies. The technique is based on Kelvin probe force microscopy (KPFM), which is widely used to study other electrically driven semiconductor devices [20,21,22,23]

Methods

Results

Conclusion