Metalorganic Chemical Vapor Deposition of GaN, AlN and GaAlN for UV Photodetector Applications.

GaN, AlN and GaAlN epilayers were grown by low-pressure metalorganic chemical vapor deposition, on sapphire, silicon, and 6H-SiC. The X-ray diffraction linewidths were as low as 30 and 100 arcsecs for GaN and AlN respectively on sapphire. Sharp optical absorption edges were obtained for these films. Transmission electron microscopy characterized the films microstructurally. Photoluminescence PL at 300 and 77 K yielded linewidths of about 80 and 40 meV respectively for GaN on all substrates. However, no deep-level-associated yellow emission was detected from the GaN on SiC. Unintentionally n-type doped GaN had an electron mobility as high as 200 sq cmVs at 300 K. As-grown semi-insulating CaN was also achieved. Ge doped GaN n-type n up to 10exp 20cu cm. P-type doping was conducted with Mg, resulting in semi-insulating layers. No yellow emission was detected from doped films. Ternary Ga1-xAlxN was grown for 0 x 1, with sharp and tailored absorption edges. Simple photoconductors were realized with GaN and Ga1-xAlxN. The lifetimes of the excess carriers were investigated. The processing of GaN and GaAlN films deposition, annealing of contacts was conducted. jg