Growth and characterization of pendeo-epitaxial GaN(112¯0) on 4H–SiC(112¯0) substrates

Growth on AlN/4H–SiC(112¯0) substrates of coalesced, non-polar GaN(112¯0) films having volumes of material with reduced densities of dislocations and stacking faults has been achieved from etched stripes via the statistical and experimental determination of the effect of temperature and V/III ratio on the lateral and vertical growth rates of the GaN{0 0 0 1} faces combined with pendeo-epitaxy. AFM of the uncoalesced GaN(0 0 0 1) and GaN (0001¯) vertical faces revealed growth steps with some steps terminating at dislocations on the former and a pitted surface without growth steps, indicative of decomposition, on the latter. Coalescence was achieved via (a) a two-step route and the parameters of (1) T=1100°C and V/III=1323V/III=1323 for 40 min and (2) 1020 °C and V/III=660V/III=660 for 40 min and (b) a one-step route that employed T=1020°C and a V/III ratio=660ratio=660 for 6 h. The densities of dislocations in the GaN grown vertically over and laterally from the (112¯0) stripes were ∼4×1010 cm−2 and ∼2×108 cm−2, respectively; the densities of stacking fault in these volumes were ∼1×106 cm−1 and ∼2×104 cm−1, respectively. The defects in the wing material were observed primarily at the bottom of the film where lateral growth of the GaN occurred from the AlN and the SiC. Plan view AFM also revealed different microstructures and a reduction in the RMS roughness values from 1.2 to 0.95 nm in these respective regions.