Improved Schottky Leakage Current of In_(0.5)Al_(0.5)As/In_(0.5)Ga_(0.5)As Metamorphic HEMTs Using (NH_4)_2S_x Treatment

摘要

Surface passivation process play an important role, especially in high-power In_(0.5)A1_(0.5)As/In_(0.5)Ga_(0.5)As metamorphic high-electron-mobility transistor (MHEMT) applications, and a passivation pretreatment technology has been proposed in this study. Before the deposition of SiN_x passivation layers, submicrometer MHEMTs were subjected in (NH_4)_2S_x solution with UV-light illumination instead of hot (NH_4)_2S_x solution. The Schottky gate turn-on voltage was improved from 0.41 to 0.52 V after (NH_4)_2S_x + 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 mu m long gate MHEMTs with (NH_4)_2S_x pretreatment exhibited a minimum noise figure (NF_(min)) of 0.46 dB and an associated gain of 18 dB at 5 GHz operation.