Global changes of the band structure and the crystal lattice of Ga(N,As) due to hydrogenation

Abstract

The effect of hydrogenation on five ${\mathrm{GaN}}_{x}{\mathrm{As}}_{1\ensuremath{-}x}$ epitaxial layers $(0.00043<~x<~0.019)$ grown by metal-organic vapor-phase epitaxy was investigated. Photomodulated reflectance (PR) and photoluminescence spectroscopy were used to study the electronic band structure, and x-ray diffraction (XRD) and Raman spectroscopy to probe, respectively, the static and dynamic properties of crystal lattice before and after hydrogenation. Hydrogen almost completely neutralizes the effect of N on the band structure of the GaAs host. The direct band gap ${E}_{\ensuremath{-}}$ and the spin-orbit split-off band ${E}_{\ensuremath{-}}+{\ensuremath{\Delta}}_{0}$ blueshift toward the corresponding energies in GaAs and the ${E}_{+}$ band disappears after hydrogenation. The PR spectra of hydrogenated ${\mathrm{GaN}}_{x}{\mathrm{As}}_{1\ensuremath{-}x}$ resemble broad GaAs-like spectra. The XRD traces reveal that hydrogenation removes the tensile strain in ${\mathrm{GaN}}_{x}{\mathrm{As}}_{1\ensuremath{-}x}$ layers and even induces compressive strain. After hydrogenation the GaAs-like features in the Raman spectra persist whereas the local vibrational mode due to N disappears. Three H-related modes can be distinguished in the Raman spectra.