GaN nucleation and growth on sapphire(0001): Incorporation and interlayer transport

GaN growth on nitridated sapphire (0001) by rf plasma-assisted metal-organi c molecular-beam epitaxy is shown to exhibit a highly superlinear growth ra te and a transition from strained, smooth growth to relaxed cluster growth during the first layer. A coupled rate-equation model suggests that the gro wth rate arises from both the site-dependent reactivity of precursor molecu les and a layer-dependent interlayer transport probability. The nitridation layer, which determines the initial strain of the GaN film, bears a striki ng resemblance to a well known Al-rich surface reconstruction of sapphire.