X-ray absorption spectroscopy for lattice-matched and strain-relaxed GaAsPBi epi-layers on GaAs (001) substrates

Abstract

GaAsPBi is a comparatively novel quaternary III–V compound semiconductor with attractive properties that suit optoelectronic applications. However, the quaternary compound synthesized on GaAs (001) is not straightforward and requires elaborately adjusted growth parameters. The quaternary compound usually presents inhomogeneity and defects, making the compositional estimation of the quaternary compound challenging. This work proposes a method to estimate the quaternary compound using synchrotron-based extended X-ray absorption fine structure (EXAFS) around the P-K edge. This technique considers only bound atoms in the local structure, making it suitable for estimating the composition of both defective and homogeneous compounds. From the EXAFS estimations, the average composition of defective GaAsPBi (homogeneous GaAsPBi) is GaAs_0.24P_0.68Bi_0.08 (GaAs_0.66P_0.25Bi_0.09). The oxidation states of Bi and P in the quaternary compounds are also probed by synchrotron-based X-ray absorption near edge structure. Finally, we show that the ex situ annealing of lattice-matched GaAsPBi epitaxial layer on GaAs (001) under the flow of hydrogen-containing gas can only slightly improve its luminescence (up to 1.3 times as compared to the as-grown condition) owing to the low defect density.