HETEROEPITAXIAL THERMAL GRADIENT SOLUTION GROWTH OF GAN

The growth of single-crystal epitaxial layers of GaN onto (0001) oriented sapphire substrates from the liquid phase is shown to require three conditions: (i) the partial pressure of NH//3 in the H//2 ambient, P//N//H//3, greater than the equilibrium pressure, (ii) the growth melt positioned in a thermal gradient to transport the dissolved GaN to the growth interface, and (iii) the control of nucleation by the addition of Bi to the growth melt. Studies of growth at temperatures from 850 degree to 1050 degree C show that the layer thickness, t, is approximately linear in time and varies with growth temperature and atom fraction of Ga, X//G//a, in the growth melt. The inability to change the electron concentration, n, with Zn doping and the decrease of n with x//G//a in the growth melt support but do not unambiguously confirm the model that the native donor is a nitrogen vacancy.