Structural changes during annealing of GaInAsN

The alloy GaInAsN has great potential as a lower-band-gap material lattice matched to GaAs, but there is little understanding of what causes its poor optoelectronic properties and why these improve with annealing. This study provides information about the structural changes that occur when GaInAsN is annealed. The Fourier transform infrared spectra exhibit two primary features: a triplet at ∼470 cm⁻¹ (Ga–N stretch) and two or three bands at ∼3100 cm⁻¹ (N–H stretch). The change in the Ga–N stretch absorption can be explained if the nitrogen environment is converted from ${\mathrm{NGa}}_{\mathrm{4}}$ to ${\mathrm{NInGa}}_{\mathrm{3}}$ after annealing. The N–H stretch is also changed after annealing, implying a second, and unrelated, structural change.