Small-Signal Analysis of High Maximum Frequency of Oscillation 0.1-μm Off-Set Gamma-Shaped Gate InGaAs/InAlAs/GaAs Metamorphic High-Electron-Mobility Transistors

摘要

We examined the effects of gate recess process conditions on the electrical characteristics of 0.1-μm-gate-length metamorphic high-electron-mobility transistors (MHEMTs) by the comparative analysis of small-signal parameters. When the wide-gate-recess method is adopted, significant reductions in gate-to-drain conductance and gate-to-drain capacitance were obtained compared with those obtained by the of narrow-gate-recess method. These differences in small-signal parameters are due to the removal of the entire n+ cap layer and corresponding dissimilarity in gate structure when the wide-gate-recess method is used. The wide-gate-recess method produced ～1/2 drain-source saturation current and extrinsic transconductance compared with the narrow-gate-recess method. In contract to the DC performances, a markedly enhanced S_(21) gain of 3.5 dB and an f_(max) of 447 GHz were obtained from the MHEMTs processed by the wide-gate-recess method. This high f_(max) is responsible for the proper selection of the gate recess method for what and is one of the best data thus far reported for 0.1 -μm-gate-length MHEMTs.