Droplet heteroepitaxy of GaN quantum dots by metal-organic chemical vapor deposition

Optically active GaN quantum dots on conductive AlGaN templates are synthesized by droplet heteroepitaxy, whereby the Ga droplets are converted to GaN islands in the presence of ammonia at 600°C. We have investigated the evolution of metallic Ga layers on AlGaN, obtaining the optimal surface densities and size distribution of the Ga droplets. The stability of GaN islands is influenced by the surface kinetics and the initial droplet size; the condition of Ga deposition and subsequent nitrogen exposure is identified, which preserves the initial density of the Ga droplets. A nitrogen-rich environment is identified as a necessary condition for maintaining the optimal GaN morphology by suppressing the Ga surface diffusion and preventing two-dimensional layer growth.