High Crystallinity and Highly Relaxed Al0.60Ga0.40N Films Using Growth Mode Control Fabricated on a Sputtered AlN Template with High‐Temperature Annealing

Abstract

Herein, a method for growing AlGaN using an intermediate AlN molar fraction on a sputtered AlN template with high‐temperature annealing via an AlN homoepitaxial layer is investigated. The growth mode dependence of AlGaN on the amount of Ga doping in the AlN homoepitaxial layer is examined in detail. As a result, homoepitaxial growth of AlN on sputtered AlN improve the surface flatness. In addition, it is found that the macroscopic flatness is improved by increasing the amount of Ga doping, but this decreases the microscopic flatness. Moreover, when Al0.60Ga0.40N is grown on homoepitaxial AlN layers with different amounts of Ga doping, a difference in the growth mode is observed, and this reveal a remarkable difference in the dislocation density of Al0.60Ga0.40N. The dislocation density dependence of the lasing threshold power density in a UV–B optical pumped laser is also investigated. As a result, the lasing threshold power density is reduced from ≈220 to 50 kW cm−2 by reducing the dislocation density from 1.6 × 109 to 8.0 × 108 cm−2. It is confirmed that it is, therefore, essential to reduce the dislocation density to reduce the threshold power density of the UV–B laser.