GaAsBi layers of various Bi concentrations have been grown by molecular beam epitaxy on GaAs substrate and studied by electromodulation spectroscopy (EM). Optical transitions related to the heavy-hole (HH) and light-hole (LH) bands as well as the spin-orbit (SO) splitoff band have been observed in EM spectra and their energies have been found to be in very good agreement with theoretical predictions, which take into account the strain-related shifts obtained from the Bir-Pikus theory implemented to the electronic band structure of GaAsBi obtained after recent DFT calculations for this alloy. The pressure coefficients for HH, LH and SO transitions have been determined from PR measurements performed at various hydrostatic pressures and discussed.

We have examined the influence of electron irradiation and rapid thermal annealing on photoluminescence emission from GaAsNBi alloys. Electron irradiation of a 1-eV compressively strained GaNAsBi-on-GaAs epilayer, grown by molecular beam epitaxy and subsequently rapidly thermally annealed, is found to induce much stronger photoluminescence than what is observed for an identical as-grown sample upon annealing. At the same time, annealing of the irradiated sample caused a negligible spectral blueshift and reduced alloy potential energy fluctuations. These irradiation-related phenomena occurred without a change in the alloy macroscopic composition as revealed by x-ray diffraction and are mainly related to the nitrogen incorporated into non-substitutional sites in the quaternary alloy.

The band offset parameters of low-boron-content BGaN/GaN heterojunctions have been studied using x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) in B x Ga 1−x N epilayers (x ⩽ 0.043) grown on GaN/sapphire and AlN/sapphire templates. A staggered-gap (type-II) band alignment has been identified at the BGaN/GaN heterojunction by XPS. A study of the red shift of deep-level-related yellow PL band and the band gap shrinkage of BGaN epilayers with increasing boron content confirmed the type-II band alignment and enabled us to estimate that the ratio of the conduction-to-valence band discontinuity is 57:43. It is also shown that the band gap bowing of the BGaN alloy system is accommodated in the conduction band.

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