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

The absorption edge of GaNxP1−x alloys (0.01⩽x⩽0.03) is shown to exhibit a direct-band gap-like behavior. Thermal variation of the band gap energy Eg, 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 Eg shift with temperature. On the contrary, an increasing contribution of Γc states, which becomes predominant for the higher compositions, leads to the larger thermal variation in Eg.