Modeling of the atomic structure and electronic properties of amorphous GaN1−xAsx

Chemically ordered 250-atom models for amorphous GaN1−xAsx alloys in the concentration range of 0.17 < x < 0.75 have been studied with density functional theory simulations, starting with initial continuous random network structures. The analysis of network topology has been achieved by examining partial-pair correlation functions, bond angle distributions, ring statistics and average coordination numbers. The electronic properties of amorphous GaN1−xAsx alloys have been estimated by means of electronic density states (EDOS) and inverse participation ratios (IPR). Our calculations indicate that the introduction of As into GaN reduces the bond angle disorder. According to our ring analysis the 250 atom a-GaN1−xAsx model has a disordered tetrahedral characteristic confirming the fact that continuous random network (CRN) can provide an ideal initial structure. The study of EDOS and IPR proves that the bandgap of a-GaN1−xAsx gets narrower with increasing As concentration, which is in good agreement with the experimental results and the band anti-crossing model.