Growth And Characterization Of Thick Gan Layers Grown By Halide Vapour Phase Epitaxy On Lattice-matched Alinn Templates

摘要

We have investigated the feasibility to use GaN lattice-matched Al_(0.82)In_(0.18)N as a starting layer for growth of thick GaN using halide vapor phase epitaxy (HVPE). The buffer, which consisted of Al_(0.82)In_(0.18)N(0001) on a 50-nm-thick TiN(111) seed layer, was grown by magnetron sputter epitaxy (MSE) on a 2" Al_2O_3(0001) substrate. It was found that the surface morphology of the GaN strongly depends on the choice of carrier gases. Using a mixture of hydrogen and nitrogen results in a rough morphology, while growth in pure nitrogen gives layers of good morphology and high transparency. For a 30-μm-thick GaN film, the threading dislocation (TD) density, as determined by cathodoluminescence, is about～3 × 10~8cm~(-2). By transmission electron microscopy (TEM), it was revealed that the threading dislocations originate from the buffer layer and the GaN/Al_(0.82)In_(0.18)N interface. The GaN/Al_(0.82)In_(0.18)N interface is roughened during growth due to a chemical incompatibility between the HVPE process and the Al_(0.82)In_(0.18)N layer. Additionally, the GaN layers are cracked due to tensile strain indicating initial growth of crystallites which eventually coalesce and hence build up a tensile stress in the film.