Photoreflectance study of the temperature dependence of excitonic transitions in dilute GaAsN alloys

Abstract

We have studied the temperature dependence of optical transitions in dilute GaAsN alloys using photoreflectance (PR). A delocalized‐state transition is clearly observed in PR spectra while several localized‐state emission lines due to isoelectronic centers appear in photoluminescence spectra. The energy of optical transitions observed in PR spectra is in agreement with the excitonic transition energy in photoluminescence excitation spectra, clearly showing that the optical transitions in PR spectra are excitonic transitions. We analyzed the temperature dependence of the excitonic transition energies using the Bose–Einstein statistical expression, and found that even dilute alloys follow the same trend as GaAsN alloys with higher nitrogen concentrations. We discuss the coexistence of localized and delocalized states in dilute GaAsN alloys in terms of the random distribution of N atoms.

Photoluminescence Mechanism in Heavily Si‐Doped GaAsN

“…[ 14,15 ] Then, some previous studies proposed that deep electron traps in GaAsN were ascribed to N cluster levels. [ 16,17 ] In addition, in our previous research, [ 18 ] electrons were revealed to exist at both deep electron traps and the shallow Si donor level in moderately Si‐doped GaAsN because these electron traps were revealed to have small density of states around the level in the order of 10 17 cm −3 . Therefore, there are two possible dominant PL processes for this moderately Si‐doped GaAsN.…”

Effects of rapid thermal annealing on two-dimensional delocalized electronic states of the epitaxial N δ-doped layer in GaAs

“…12,13 In the impurity limit, N pair centers in GaAs act as isoelectronic traps below the conduction-band edge because of a strong electronegativity of N atoms. 9,[14][15][16] The electronic state of the localized impurity level is uniquely determined by the N pair structure in GaAs, thereby electronic coupling among high-density N pair centers enables to form a quasi epitaxial sheet. By increasing the N d-doping density, we observed a change in the electronic states in the N d-doped GaAs from the isolated impurity centers to the delocalized impurity band at 1.49 eV according to the photoluminescence (PL) spectroscopy.…”