Temperature dependence of the GaNxP1-x band gap and effect of band crossover

The absorption edge of GaNxP1-x alloys (0.01less than or equal toxless than or equal to0.03) is shown to exhibit a direct-band gap-like behavior. Thermal variation of the band gap energy E-g, however, is found to be the same or even smaller than that for the indirect band gap of GaP and depends on the N content. The effect is tentatively attributed to the following counteracting contributions to the band edge formation. An interaction with N-related localized states, especially significant in the vicinity of band crossover (e.g., x=0.013), causes a substantial slow down of the E-g shift with temperature. On the contrary, an increasing contribution of Gamma(c) states, which becomes predominant for the higher compositions, leads to the larger thermal variation in E-g. (C) 2002 American Institute of Physics.