Al_0.17Ga_0.83N Film Using Middle-Temperature Intermediate Layer Grown on (0001) Sapphire Substrate by Metal-Organic Chemical Vapor Deposition

The reduction of the dislocation density in a high-temperature (HT)-Al_0.17Ga_0.83N epitaxial layer was achieved by a middle-temperature (MT)-intermediate layer technique, in which the HT and the MT were 1050 and 950 °C, respectively. For one set of the MT-intermediate layer, the structure was 4.5-µm-thick HT-Al_0.17Ga_0.83N/1-µm-thick MT-intermediate layer/100-nm-thick HT-Al_0.17Ga_0.83N layer/low-temperature (LT)-GaNP buffer/trenched (0001) sapphire. The full-width at half maximum values of (0002) and (1012) diffraction peaks of the X-ray diffraction for the Al_0.17Ga_0.83N epitaxial layer using one set of the MT-intermediate layer were improved to 359 and 486 arcsec compared with 401 and 977 arcsec for the film without the MT-intermediate layer technique, respectively. Transmission electron microscopy result showed that the dislocation density in the Al_0.17Ga_0.83N film using one set of MT-intermediate layer was reduced from (1–4)×10¹⁰ to 1.7×10⁹ cm^-2. The Al_0.17Ga_0.83N epitaxial film including two sets of MT-intermediate layers improved the most, showing a dislocation density of 9.3×10⁸ cm^-2.