Semipolar (202¯1) GaN laser diodes operating at 388 nm grown by plasma-assisted molecular beam epitaxy

Abstract

Laser diodes (LDs) were grown by plasma-assisted molecular beam epitaxy on semipolar (202¯1) GaN substrates. Metal-rich conditions provided smooth surface morphology and good structural quality as confirmed by atomic force microscopy and transmission electron microscopy studies. No stacking faults or any linear defects were formed during the growth in the InGaN/InGaN multiquantum well active region. Devices were processed with ridge-waveguide along the [1¯21¯0] direction. Mirrors were cleaved or fabricated by focused ion beam (FIB) processing. LDs operated at 388.2 nm with the threshold current density 13.2 kA/cm2 and the threshold voltage 10.8 V. The device with mirrors fabricated by FIB processing reached practically the same threshold current and slope efficiency as the one with cleaved mirrors. The authors present the beneficial role of the InGaN optical confinement layers in semipolar LDs, which can be optimized to improve the threshold current of these devices.