Spatially resolved cathodoluminescence study of As doped GaN

The introduction of arsenic (As) into GaN to produce a group-V ternary alloy has been of much recent interest, mostly because of the prospect of reducing 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 series of samples varies from 3.4 × 10¹⁷ to 4.2 × 10¹⁸ cm^-3. The data are presented to show how As effects the optical properties of GaN. Our focus is on the nature of the strong luminescence band found at ∼475 nm. The intensity of the GaN near bandedge emission is shown to decrease and the 475 nm emission to increase with As content. This is attributed to the large As atoms disrupting the GaN lattice and creating defects or stacking faults that act as non-radiative centers. We have used scanning electron microscopy (SEM) and cathodoluminescence (CL) to investigate the spatial uniformity of the ∼475 nm emission in these materials and show that the luminescence is inhomogeneous indicating arsenic segregation.