Effects of AIN and GaN low-temperature interlayers on the dislocation behaviour of AlGaN and GaN grown by MOCVD

This chapter investigates in the transmission electron microscope (TEM) the effects of introducing two AIN and GaN low-temperature (LT) interlayers during the growth of AIGaN and GaN by metal organic chemical vapour deposition. It compares AIGaN samples with and without AIN interlayers, equally spaced within the bulk epilayer, and report differences in the threading dislocation density and behaviour. Group-III nitrides are the most promising candidates for short-wavelength semiconductor lasers because of their wide, direct bandgaps ranging from 0.8 eV (InN) to 6.2 eV (AIN). The GaN and AlGaN epilayer samples were grown by low-pressure metal-organic chemical vapour deposition in a Thomas Swan 6x2 inch Close-Coupled Showerhead reactor. For AlGaN samples A and B a thin AIN NL, nominal thickness of 30 nm, was deposited at 700°C, after which the temperature was ramped to 1030 oc in a flow of ammonia and hydrogen.