Spatially resolved cathodoluminescence study of As doped GaN

The introduction of arsenic (As) into GaN to produce a group-V ternary allo y has been of much recent interest, mostly because of the prospect of reduc ing the GaN bandgap. We have performed a systematic study of the role of As in GaN grown by molecular beam epitaxy (MBE). The As content of this serie s of samples varies from 3.4 x 10(17) to 4.2 x 10(18) cm(-3). The data are presented to show how As effects the optical properties of GaN. Our focus i s on the nature of the strong luminescence band found at similar to 475 nm. The intensity of the GaN near bandedge emission is shown to decrease and t he 475 nm emission to increase with As content. This is attributed to the l arge As atoms disrupting the GaN lattice and creating defects or stacking f aults that act as non-radiative centers. We have used scanning electron mic roscopy (SEM) and cathodoluminescence (CL) to investigate the spatial unifo rmity of the similar to 475 nm emission in these materials and show that th e luminescence is inhomogeneous indicating arsenic segregation.