Sapphire substrate off-angle and off-direction dependences on characteristics of AlGaN-based deep ultraviolet light-emitting diodes

摘要

We investigated dependences of sapphire substrate off-angle from 0.2 degrees to 3.0 degrees and off-direction (a-axis or m-axis) on the device characteristics of the AlGaN quantum-well deep ultraviolet LEDs emitting 280-290 nm. We found that the terrace regions of the LEDs showed a lower threading dislocation density, while the step-edge regions of the LEDs contain more threading dislocations, more Ga, and thicker well widths. The emissions from the terrace regions of the LED with the off-angle were dominant at higher current injection. Finally, the light output power from the LED with the m-axis 1.0 degrees off was the highest among the samples. We then developed a model to explain the above optical properties of our deep ultraviolet LEDs with off-angles. (C) 2019 The Japan Society of Applied Physics