Abstract
Al0.23Ga0.77N/GaN and Al0.27Ga0.73N/GaN epitaxial layers were grown on sapphire substrates by metal organic chemical vapour deposition (MOCVD). The in-plane strain (εxx) values were found to be -2.4 ×10-4 and -2.8 ×10-4 for Al0.23Ga0.77N and Al0.27Ga0.73N layers using asymmetric reciprocal space mapping (RSM). Surface morphology and emission properties of the samples were analysed using atomic force microscopy (AFM) and photoluminescence spectroscopy (PL) respectively. Circular Transmission Line Measurement (CTLM) technique was adopted to find the variation in contact resistance (Rc), transfer length (LT) and specific contact resistance (ρc) between metal contacts (Ti/Al/Ni/Au: 200/1000/200/1000 Å) and AlxGa1-xN layers.A minimum specific contact resistance, ρc of about 7.81x10-6 Ωcm2 was obtained for Ti/Al/Ni/Au contact on the Al0.23Ga0.77N layer. The device characteristics were correlated with the structural and surface quality of AlxGa1-xN layers.
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