Formation of self-organized GaN dots on Al_0.11Ga_0.89N by alternating supply of source precursors

The self-organized GaN dot structure is successfully grown on a slightly lattice-mismatched Al_0.11Ga_0.89N epilayer using flow-rate modulation epitaxy (FME) growth technique. From the variation of dot density with growth temperature, we can observe that the GaN dot growth is controlled predominately by the surface diffusion of Ga adatoms at substrate temperatures below 915°C and by re-evaporation at higher temperatures. Because of the special alternating gas supply feature in FME, during the Ga source step, it is the Ga metal that is deposited on the underlying Al_0.11Ga _0.89N layer. This is because of the large lattice mismatch of 41.8% between the Ga metal (4.51 Å) and Al_0.11Ga_0.89N (3.18 Å). We consider that the GaN dot growth in our study is mainly through the Volmer-Weber growth mode, not the commonly used Stranski-Krastanow growth mode.