Investigation of Critical Problems in GaN/AIGaN Modfets

摘要

MBE AlN layers have been optimized on sapphire substrates. MBE GaN layers have been optimized with ammonia and RF nitrogen sources and Ga polarity films have been consistently obtained using both ammonia and RF nitrogen. With ammonia grown GaN, excellent X-Ray diffraction (1.6 and 3.2 arcmin FWHM values for 002 and 104 diffraction peaks), and PL with only the exciton peak dominating at 10 K with 95 % radiative efficiency have been in 0. 4 micrometer thick films. The roughness is under 1 nm. Polarization effects on MODFETs have been theoretically treated by effective mass and tight binding calculations in collaboration with Prof. Aldo DiCarli of Universita' di Roma Tor Vergata. Defects in GaN as manifested in optical transitions have been analyzed. Photoenhanced Electro Chemical (PEC) etching in conjunction with cross-sectional AFM has been developed to investigate structural defect density and correlate them to MBE growth conditions. Initial development of EFM as pertained to polarization issues in GaN has been initiated.