Effect of v iii ratio and irradiation Induced defects on structural Optical electrical and device Characteristics of gallium nitride

Abstract

newlineGallium nitride GaN is one of the most promising materials newlineamong group III nitrides because it has a direct bandgap of 3 4 eV making its newlinealloys the best candidate for devices operating in the blue or UV region of the newlineelectromagnetic spectrum GaN is mainly used in light emitting diodes newline LEDs laser diodes LDs ultraviolet detectors colour displays and newlinemicrowave devices GaN is the favourable material system for hightemperature newlineand high power electronic devices newlineGaN and its alloys are commercially grown by employing Metal newlineOragnic Chemical Vapor Deposition MOCVD technique Inspite of peculiar newlineProperties advantages and numerous applications of GaN there are many newlinetechnical challenges associated with the growth and processing of GaN alloy newlinesystems Most specifically lack of commercially available native substrates newlinehas forced the researchers to use substrates with mismatched lattice constants newlineand thermal expansion coefficients Group III nitride device development still newlinesuffers from mismatched heteroepitaxial growth Mismatch in lattice newlineconstants and thermal expansion coefficients between substrate mostly newlinesapphire or SiC and epitaxial layer inhibits perfect crystal formation newlineresulting in high densities of point defects and dislocations In heteroepitaxial newlineGaN threading dislocations as high as 109 1011 cm 2 are common unless newlinespecialized multi step regrowth methods are being applied newline