Experimental investigation of the variation of the absorption coefficient with nitrogen content in GaAsN and GaInAsN grown on GaAs (001)

Abstract

We have measured the absorption coefficient at the fundamental band edge in Ga1−yInyAs1−xNx and GaAs1−xNx alloys. In contrast to what is observed in most III-V semiconductors, the absorption coefficient of Ga(In)AsN increases when the band gap energy decreases. In the Ga1−yInyAs1−xNx alloys, the absorption coefficient at threshold saturates near x=0.009, whereas the absorption coefficient of the GaAs1−xNx layers shows no sign of saturation for 0<x<0.016. Furthermore, the value of the absorption coefficient at threshold is higher for Ga1−yInyAs1−xNx layers than for indium-free GaAs1−xN films with the same nitrogen content, a result opposite to what is observed for the nitrogen-free GaInAs alloy. The comparison of our results with calculations performed using the k⋅p formalism suggests that the proper description of the optical properties of Ga(In)AsN alloys must go beyond the effective mass approximation.