Fabrication of high crystalline AlN/sapphire for deep UV-LED

Abstract

For the realization of highly efficient deep-ultraviolet light-emitting diodes (DUV-LEDs) based on III-nitride semiconductors, it is essential to improve the crystalline quality of the AlN templates for crystal growth of AlGaN. Our group has suggested sputtering deposition and post-deposition high-temperature face-to-face annealing (FFA) as a fabrication method of AlN films with low threading dislocation density (TDD) on sapphire substrates. Although the FFA enables reduction of TDDs, it possibly causes a cracking for AlN films due to a large thermal expansion coefficient mismatch between AlN and sapphire. In this work, we controlled the residual stress in AlN films by modifying the sputtering conditions. Consequently, we achieved crack-free AlN films with low TDDs.