Dependence of GaN Channel Thickness on the Transistor Characteristics of AlGaN/GaN HEMTs Grown on Sapphire

Various GaN channel thicknesses (0.5, 2.0, 3.5 and 6.3 mu m) grown by metal organic vapor chemical deposition (MOCVD) on sapphire substrate were prepared to investigate the effects of the channel thickness on the transistor characteristics. X-ray diffraction (XRD), pulsed I-D(V-D), as well as gate stress and DC measurements were employed in this study. The results have revealed that charge trapping in the AlGaN/GaN hetero-structure is reduced and transistor performance is improved as the GaN channel thickness is increased up to a certain value (T-GaN_Channel = 3.5 mu m); More specifically, as the GaN channel thickness is increased from 0.5 mu m to 3.5 mu m, the sheet resistance and carrier mobility values are changed from 475 to 400 Omega/square and 780 to 1100 cm(2)/Vs, respectively. These results are attributed to the ameliorated crystalline quality when the GaN thickness increases as evidenced by the XRD data. (C) 2016 The Electrochemical Society. All rights reserved.