Conclusions Introduction Conventional III ndash

5. Conclusions
1. Introduction
Conventional III–V molecular beam epitaxy (MBE) growth is typically performed under group-V rich conditions. It has been known for some time that state-of-the-art GaN grown by plasma-assisted MBE requires slightly Ga-rich conditions [1] at very high substrate temperatures (~700–800 °C). Early work [1] asserted that N-rich conditions led to three-dimensional, columnar growth and low Bafilomycin A1 mobilities [2]. Some research has concluded that growth must be done with the fluxes set to obtain films as close to the stochiometric condition as possible [3], while others maintain that it must be done in the ‘intermediate range’ (Ga-rich but just short of droplet formation) [4] and [5]. In any case the window for obtaining Ga rich films without inducing Ga droplet formation is small, and precise determination of the 1:1 condition is important.
For Ga-rich conditions, the GaN (0001) surface is terminated by approximately one bilayer of Ga atoms [6], [7] and [8], which results in a smoother morphology than found in films grown under N rich conditions [9] and [10]. Feenstra et al., explains in detail the mechanisms of the N-rich and Ga-rich growth modes, and also discusses region of division while the Ga-rich conditions lead to smoother films, there is a cost to be paid in terms of Ga-droplet formation and leakage 'Bafilomycin current induced by Ga-filled threading dislocation cores [9].