<title>Recent developments of ultraviolet materials based on GaN for remote sensing</title>

Abstract

In this paper we present recent developments made in recent years on the advancement of ultraviolet (UV) materials based on GaN and related materials for remote sensing applications. Most research on III-nitride materials has been focused on lasers and light emitting devices. However, GaN and related materials (wide band gap materials) offer the possibility of improved quantum efficiency, intrinsic solar blindness, and adjustable UV threshold wavelengths. The band edge absorption is one of the fundamental parameters that one has to address when a UV detector or sensor is fabricated from GaN thin films or other related materials. New results on the temperature dependence of the optical absorption near the band edge of GaN thin films grown by different techniques will be presented. The results indicate that the band gap energy and its behavior as a function of temperature is sample dependence. The sample dependency is explained in terms of the presence of defects, extended defects, and dislocations introduced during growth. Despite the presence of a high dislocation density in GaN thin films (in the order of 10<SUP>9</SUP> cm<SUP>-3</SUP>), free and bound exciton lines were observed.