Near band-edge and excitonic behavior of GaAsN epilayers grown by Chemical Beam Epitaxy

Abstract

Photoluminescence and absorption spectroscopy experiments were performed on as grown and thermally annealed GaAs1-xNx with nitrogen content in the range of 0.75–7.1%. At low temperature, the photoluminescence spectra exhibits two set of features: (i) a relatively broad peak at low energy and near to the vicinity of the predicted band gaps and (ii) a sharp excitonic feature at higher energy (about 100 meV for x>4%). Post growth thermal annealing processes systematically favor stronger excitonic emissions, and a notable intensity reduction of the deeper (defect related) luminescence. The low temperature binding energy of the higher energy excitonic peak is found to be consistent with the increase of the electronic effective masses. A careful examination of the data obtained in this work suggests that for higher nitrogen content (x>4%), the fundamental band gap of GaAsN is located at significantly higher energies than those commonly accepted for these alloys.

Effect of residual hydrogen and temperature on initial growth stages and properties of GaAs1−xNx

“…The low-temperature PL of samples that were fabricated under conditions of low hydrogen partial pressure is characterized by a set of peaks that exhibit excitonic characteristics (quadratic excitation dependence). Their position is consistent with the expected excitonic transitions E 71/2 and E 73/2 , light and heavy hole to electron splitbands, respectively, resulting from the nitrogen-induced band-gap shift and the tetragonal deformation of the lattice strain [16] (Fig. 3).…”

Quantum tunneling design for ultra-fast photogenerated carrier collection in p-i-n III–V quantum confined solar cells

“…Note the extended range of the maximum of the transmission probability as the value of the electric field is increased, This selection not only satisfies the condition of shallow confinement for holes but also is almost lattice matched to GaAs (according to figure 1), thereby minimizing any strain induced defects in addition to displaying a fairly low band gap of 1,12 eV, At zero electric field, the structure presents a high transmission probability only in a narrow energy range close to the band gap of the barrier (1.42 eV). Nevertheless the application of few kV/cm electric field, in the order of the field at operation, substantially enlarges this high transmission probability energy range due to increased resonant tunneling effects, From previous experimental studies, an increase in the electronic effective mass has been deduced in GaAsN epilayers grown on GaAs [14]. The subsequent increase of the absorption coefficient means that less material will be needed for the absorption of the incoming photon flux.…”

“…The observation of unusually large band gap lowering upon incorporation of a small amount of nitrogen in GaAs [12] has opened a window on a whole new family of materials that present new opportunities for innovative devices, including photovoltaics [13][14][15][16]. Unlike GaN, GaBi have a larger lattice parameter than GaAs.…”

Single Carrier Resonant Tunneling Design for Improving Carrier Collection in Quantum Confined Solar Cells

“…From previous experimental studies, an increase in the electronic effective mass has been deduced in GaAsN epilayers grown on GaAs [16]. The subsequent increase of the absorption coefficient means that less material will be needed for the absorption of the incoming photon flux.…”

“…The observation of unusually large band gap lowering upon incorporation of a small amount of nitrogen in GaAs [14] has opened a window on a whole new family of materials that present new opportunities for innovative devices, including photovoltaics [15][16][17][18]. Unlike GaN, GaBi and InAs have a larger lattice parameter than GaAs.…”