Layer transferred UV emitting hBN/AlGaN heterostructures

Abstract

p-hBN/n-AlGaN heterojunctions were fabricated using a dry-selective lift-off/transfer of Mg-doped hexagonal boron nitride (hBN) layer on top of n-AlGaN. Electrical contacts were used as mechanical stressors to provide structural rigidity to hBN layers as well as enabling selective lift-off. These junctions exhibit a rectifying behavior with a rectification ratio of approximately 3 × 105 at 3 V. When junctions were forward biased, ultraviolet (UV) emission around 262 nm was measured. This emission corresponds to recombinations in the n-AlGaN layer, demonstrating good hole injection in the structure. Full light emitting diode (LED) structures were fabricated by integrating UV multi quantum wells (MQWs) into these junctions. Produced UV LEDs emit around 290 nm serving as a proof of concept for future layer transferred p-hBN/MQWs/n-AlGaN structures in which the Al content is increased to go toward deep ultraviolet (DUV) emission. The selective pick and place process used to build these LEDs has multiple advantages. First, it allows independent optimization of the p-side as well as of the n-side, which includes the quantum wells. Second, UV MQWs are protected from the high temperatures needed for high hBN material quality growth, and thus their thermal stability is not affected.