Discrete and continuous spectrum of nitrogen-induced bound states in heavily doped GaAs1-xNx - art. no. 085205

We perform a spectroscopic study on GaAs1-xNx samples with N concentrations near an important value of x=0.1%, an intermediate concentration between t he impurity limit and the alloy region. We find that near x similar to0.1%, samples exhibiting seemingly different spectra as reported in the literatu re and observed in our measurements actually have the same underlying elect ronic structure. Namely, the shallow N-induced bound states have already fo rmed an impurity band and thus led to an observable band-gap reduction, but deeper N-related bound states persist as discrete levels below the newly f ormed band edge. The role of these discrete states in the formation of the new band edge on further increasing the N doping levels is discussed. We po int out that although the nitrogen bound states form an impurity band in he avily N-doped GaAs, the states constituting such a newly formed band contin ue to retain certain localization characteristics of the impurity in the di lute limit. We observe that the impurity band gives rise to strong resonant Raman scattering, which makes it possible To obtain the resonant Raman pro file near the direct band edge of this direct-gap semiconductor.