Improved schottky leakage current of in0.5Al0.5As/ In0.5Ga0.5As metamorphic HEMTs using (NH4) 2Sx treatment

Abstract

Surface passivation process play an important role, especially in high-power In0.5Al0.5As/ln0.5Ga0.5As metamorphic high-electron-mobility transistor (MHEMT) applications, and a passivation pretreatment technology has been proposed in this study. Before the deposition of SiNx, passivation layers, submicrometer MHEMTs were subjected in (NH4)2Sx solution with UV-light illumination instead of hot (NH4)2Sx solution. The Schottky gate turn-on voltage was improved from 0.41 to 0.52 V after (NH4)2Sx + UV-light treatment due to the reduction of surface leakage current. Besides, the surface state density was also enhanced by this process, resulting in a higher current density and a higher input power swing range. The passivated 0.2 μm long gate MHEMTs with (NH4)2Sx pretreatment exhibited a minimum noise figure (NFmin) of 0.46 dB and an associated gain of 18 dB at 5 GHz operation. © 2006 The Electrochemical Society. All rights reserved.