Growth of cubic and hexagonal GaN on (0001) sapphire by ECR-MBE with various electric biases

摘要

GaN is well known to have two types of crystal structure; stable hexagonal wurtzite GaN (h-GaN) and metastable cubic zincblende GaN (c-GaN). To date a numerous study to obtain high-quality c-GaN have been performed [1] because of its advantage for fabrication of laser diode with cleaved mirrors. Most of these studies have used substrates with cubic crystal such as GaAs (001), 3C-SiC (001) and Si (001). However, it was reported recently that c-GaN could be deposited even on hexagonal sapphire (001) substrate under specific growth conditions such as low substrate temperature [2] and low V/III ratio [3, 4]. Also in ourprevious study, the c-GaN was obtained by changing the electric bias voltage applied to the sapphire (0001) substrate during GaN growth by electron-cycloctron-resonance plasma-excited molecular beam epitaxy (ECR-MBE) [5]. This structural change from hexagonal to cubic was successfully explained by effective V/III change induced by the electric bias. The bias voltage change method gives us potential to grow sparp hexagonal and cubic interfaces and superlattice structures. In this paper, structural characterization of the GaN layer including cubic and hexagonal phases grown on spphire (0001) substrate with various electric biases has been performed.