Below-bandgap photoluminescence from GaAs substrates induced by pre-MBE-growth treatments

Ronel Christian Roca,Mikihito Suzuki,Itaru Kamiya,Kosei Fukui,Hiroto Mizuno

doi:10.1063/1.5102088

Abstract

We report the observation of below-GaAs-bandgap photoluminescence (PL) emission from semi-insulating GaAs substrates subjected to thermal annealing during the standard pre-MBE-growth processes. The below-GaAs-bandgap luminescence from defects were investigated using a combination of PL techniques including below-gap-excitation (BGE) and backside illuminated (BI) PL. Using BGE and BI PL, defects deep within the substrates were probed, and their spatial positions along the sample were analyzed. A PL peak at 1000 nm was observed after pre-bake annealing at 300°C, and further peaks at 905, 940 and 1150 nm were found after oxide desorption annealing at 600°C. These are attributed to the Ga-vacancy related defect, Ga-vacancy-complex defect, As-vacancy defect, and InGaAs states, respectively. This is the first report of the formation of such optically-active defects after annealing of GaAs at moderate temperature ranges (≤600°C), providing guidelines to distinguish desired electronic states for device applications from those that arise from defects which often confuse, and also degrade the device performances.

Highlights

GaAs-based devices for near infrared (NIR) telecommunications
The short-wavelength 850-nm (780–980 nm)1–4 band, that is dominated by devices that are grown on GaAs substrates, is still seeing continuous improvements in recent years
The longwavelength 1310- and 1550-nm (1260–1625 nm)1,2 bands, that have traditionally been dominated by devices grown on InP substrates,7,8 are starting to be challenged by novel InGaAs quantum wells (QW)9,10 and InAs quantum dots (QD)11–15 -based devices grown directly on GaAs substrates

Summary

Introduction

GaAs-based devices for near infrared (NIR) telecommunications. The short-wavelength 850-nm (780–980 nm)1–4 band, that is dominated by devices that are grown on GaAs substrates, is still seeing continuous improvements in recent years.5,6 Whereas, the longwavelength 1310- and 1550-nm (1260–1625 nm)1,2 bands, that have traditionally been dominated by devices grown on InP substrates,7,8 are starting to be challenged by novel InGaAs quantum wells (QW)9,10 and InAs quantum dots (QD)11–15 -based devices grown directly on GaAs substrates. As will be shown in proceeding results, the spectra from all samples seem to suggest the presence of the GaAs antisite and EL2 defects, based on the gradual increase in the PL intensity for wavelengths >1200 nm.

Results

Conclusion