Effects of dry processing on the optical properties of GaN

Abstract

Effects of dry processing on the band-edge, blue, and yellow luminescence behavior of GaN surfaces exposed to SF6 and Ar plasmas have been investigated. Our results indicate that a higher concentration of donor-related defects are introduced on the top 100 nm GaN surface after Ar compared to SF6 plasma treatment. The higher defect concentration can be correlated to the yellow luminescence. In particular, the sample exposed to Ar plasma exhibits a factor of 20 increase in yellow luminescence intensity compared to the unetched sample. This effect is attributed to the introduction of defects—metastable states on the GaN surface after ion bombardment. Using a laser beam in the ultraviolet region, we have been able to write to and read from regions on the Ar-bombarded GaN surface. We demonstrate that the presence of reactive ion etch-induced metastable defects is central to the observed enhanced optical memory effect. The metastable states are identified as nitrogen deficient surfaces limited to the top few monolayers, as well as unidentified defect propagation down to 100 nm from the etched surface.