Investigation of enhancement-mode metamorphic InAlAs/InGaAs HEMTs by Schottky metal diffusion

In this report, we have developed the enhancement mode (E-mode) InAlAs/InGaAs metamorphic HEMT's (mHEMTs) on GaAs substrates by using the thermally annealed Schottky metal diffusion approach. The activation energy of platinum (Pt) Schottky metal was systematically carried out. Based on the extracted device small-signal model, the improved devices rf transconductance (g/sub m/) is more significantly than the increased gate-to-source capacitance (C/sub gs/) after the Schottky metal diffusion, due to the reduction of gate-to-channel separation. Moreover, it also exhibits a high voltage gain and capacitance ratio resulting in a higher maximum oscillation frequency.