Electrical characterisation of deep level defects in Be-doped AlGaAs grown on (100) and (311)A GaAs substrates by MBE

Riaz H Mari,David Taylor,Mohsin Aziz,Almontaser Khatab,Mohamed Henini,Muhammad Shafi

doi:10.1186/1556-276x-6-180

Abstract

The growth of high mobility two-dimensional hole gases (2DHGs) using GaAs-GaAlAs heterostructures has been the subject of many investigations. However, despite many efforts hole mobilities in Be-doped structures grown on (100) GaAs substrate remained considerably lower than those obtained by growing on (311)A oriented surface using silicon as p-type dopant. In this study we will report on the properties of hole traps in a set of p-type Be-doped Al0.29Ga0.71As samples grown by molecular beam epitaxy on (100) and (311)A GaAs substrates using deep level transient spectroscopy (DLTS) technique. In addition, the effect of the level of Be-doping concentration on the hole deep traps is investigated. It was observed that with increasing the Be-doping concentration from 1 × 1016 to 1 × 1017 cm-3 the number of detected electrically active defects decreases for samples grown on (311)A substrate, whereas, it increases for (100) orientated samples. The DLTS measurements also reveal that the activation energies of traps detected in (311)A are lower than those in (100). From these findings it is expected that mobilities of 2DHGs in Be-doped GaAs-GaAlAs devices grown on (311)A should be higher than those on (100).

Highlights

High index planes have attracted a great deal of attention for the production of high quality epitaxially grown semiconductor materials
Three and four hole traps are observed in the samples grown on (100) plane for doping concentrations of 1 × 1016 and 3 × 1016 cm-3, respectively
In summary, we studied the effect of different Be-doping concentrations in AlGaAs layers grown on (100) and (311)A GaAs substrates

Summary

Introduction

High index planes have attracted a great deal of attention for the production of high quality epitaxially grown semiconductor materials. Photoluminescence studies have been carried out by Galbiati et al [7] to investigate the effect of Be incorporation and higher hole mobility in MBE grown p-type AlGaAs on (100) and (311)A GaAs orientations. This enhancement of charge mobility and better PL efficiency was suggested to be due to a reduction of electrically active hole traps in (311)A epilayers as compared to those grown on (100) substrates.

Results

Conclusion