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The band-anticrossing (BAC) model has been widely applied to analyse the electronic structure of dilute nitride III-V-N alloys such as GaN x As 1−x . The BAC model describes the strong band gap bowing observed at low N composition in GaN x As 1−x in terms of an interaction between the GaAs host matrix conduction band edge and a higher lying band of localized N resonant states. In practice, replacing As by N introduces a range of N-related defect levels, associated with isolated N atoms, N-N pairs and larger clusters of N atoms. We show that the effect of such defect levels on the alloy conduction band structure is strongly dependent on the relative energy of the defect levels and the host conduction band edge. We first consider GaN x As 1−x , where we show that the unexpectedly large electron effective mass and gyromagnetic ratio, and their non-monotonic variation with x, are due to hybridization between the conduction band edge and specific nitrogen states close to the band edge. The N-related defect levels lie below the conduction band edge in GaN x P 1−x . We must therefore explicitly treat the interaction between the higher lying GaP host conduction band minimum and defect states associated with a random distribution of N atoms in order to obtain a good description of the lowest conduction states in disordered GaPN alloys. Turning to other alloys, N-related defect levels should generally lie well above the conduction band minimum in InNSb, with the band dispersion of InNSb then well described by a two-level BAC model. Both InP and InAs are intermediate between InSb and GaAs. By contrast, we calculate that N-related defect levels lie close to the conduction band minimum in GaNSb, and will therefore strongly perturb the lowest conduction states in this alloy. Overall, we conclude that the BAC model provides a good qualitative explanation of the electronic properties of dilute nitride alloys, but that it is in many cases necessary to include the details of the distribution of N-related defect levels to obtain a quantitative understanding of the conduction band structure in dilute nitride alloys.

Deuterium (hydrogen) incorporation in dilute nitrides (e.g., GaAsN and GaPN) modifies dramatically the crystal's electronic and structural properties and represents a prominent example of defect engineering in semiconductors. However, the microscopic origin of D-related effects is still an experimentally unresolved issue. In this paper, we used nuclear reaction analyses and/or channeling, high resolution x-ray diffraction, photoluminescence, and x-ray absorption fine structure measurements to determine how the stoichiometric [D]/[N] ratio and the local structure of the N-D complexes parallel the evolution of the GaAsN electronic and strain properties upon irradiation and controlled removal of D. The experimental results provide the following picture: (i) Upon deuteration, nitrogen-deuterium complexes form with [D]/[N]=3, leading to a neutralization of the N electronic effects in GaAs and to a strain reversal (from tensile to compressive) of the N-containing layer. (ii) A moderate annealing at 250 degrees C gives [D]/[N]=2 and removes the compressive strain, therefore the lattice parameter approaches that of the N-free alloy, whereas the N-induced electronic properties are still passivated. (iii) Finally, annealings at higher temperature (330 degrees C) dissolve the deuterium-nitrogen complexes, and consequently the electronic properties and the tensile strain of the as-grown GaAsN lattice are recovered. Therefore, we conclude that the complex responsible for N passivation contains two deuterium atoms per nitrogen atom, while strain reversal in deuterated GaAsN is due to a complex with a third, less tightly bound deuterium atom

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Detailed measurements and theoretical analysis are presented of the far-infrared absorption coefficient of phosphorous donors in uncompensated silicon at low temperatures. The study covers over 3 orders of magnitude in doping density, i.e., from the regime of isolated donors to near the insulator-metal transition at 3.7×1018 cm-3. The photon energy was varied from 5% of the isolated donor ionization energy (45.5 meV) to about 25% above it. The spectra are described quantitatively by including pair states (donor excitons), charge-transfer excitations at low densities and energy, and excitation processes in larger random clusters at higher densities. The results indicate that the donors form a nearly ideal, random, three-dimensional system in which there are large-scale potential fluctuations which dominate the approach to the delocalization transition. © 1981 The American Physical Society

In x Ga 1−x As 1−y N y / GaAs single quantum wells emitting at room temperature in the wavelength range λ=(1.3–1.55) μm have been studied by photoluminescence (PL). By increasing temperature, we find that samples containing nitrogen have a luminescence thermal stability and a room temperature emission efficiency higher than that of the corresponding N-free heterostructures. The temperature dependence of the PL line shape shows a progressive carrier detrapping from localized to extended states as T is increased. Finally, the extent of the thermal shift of the free exciton energy for different y indicates that the electron band edge has a localized character which increases with nitrogen content.

The electron effective mass, m e , has been determined by magnetophotoluminescence in as-grown and hydrogenated GaAs 1−x N x samples for a wide range of nitrogen concentrations ͑from x Ͻ 0.01% to x = 1.78%͒. A modified k·p model, which takes into account hybridization effects between N cluster states and the conduction band edge, reproduces quantitatively the experimental m e values up to x ഛ 0.6%. Experimental and theoretical evidence is provided for the N complexes responsible for the nonmonotonic and initially puzzling compositional dependence of the electron mass.