High quality ultraviolet AlGaN/GaN multiple quantum wells with atomic layer deposition grown AlGaN barriers

Abstract

Low dislocation density ultraviolet (UV) AlGaN/GaN multiple quantum well (MQW) structure was grown using atomic layer deposition (ALD) technique. The AlGaN/GaN MQW grown on the sapphire substrate consisted of three GaN QWs and four AlGaN barriers formed by ALD grown AlN/GaN superlattices. The as-grown sample showed smooth surface morphology with a root-mean-square roughness value of only 0.35 nm, and no surface cracks were found. The dislocation density was estimated to be as low as 3.5 x 10(7) cm(-2). X-ray and transmission electron microscope data showed the MQW had sharp interfaces with good periodicity. The sample had an UV photoluminescence emission at 334 nm (3.71 eV) with a very narrow linewidth of 47 meV at 13 K. The cathodoluminescence image revealed a fairly uniform luminescence pattern at room temperature. The AlGaN/GaN MQW grown by ALD technique should be useful for providing high crystalline quality for fabrication of various optical devices. c 2008 American Institute of Physics.