Reduced temperature dependence of the band gap in GaAs1-yNy investigated with photoluminescence -: art. no. 235325

The effect of the temperature (T) on the band-gap energy (E-g) of hydrogenated GaAs1-yNy/GaAs quantum wells has been studied by photoluminescence from 10 to 540 K. Nitrogen insertion in GaAs leads to a sizable decrease of E-g and to a flattening of the band-gap dependence on T with respect to that of bare GaAs. Atomic hydrogen irradiation passivates nitrogen in GaAs1-yNy and leads to an increase of E-g, which is accompanied by an increase in the thermal shrinkage rate (S) of the band gap. Eventually, a strong correlation between S and the concentration of unpassivated N atoms is found. The wide temperature range investigated and the hydrogen induced effects permit to claim that the reduced thermal redshift of the gap in N containing samples: (i) cannot be ascribed to the reduction of the pressure coefficients in Ga(AsN); (ii) can be accounted for, instead, by a cancellation of the Debye-Waller and self-energy terms in the T dependence of the band gap. The latter effect is explained in terms of a recently proposed increase in the localized character of the conduction band edge with increasing N concentration.