Improved Transconductance of AlGaAs/GaAs Heterostructure FET with Si-Doped Channel

The n+ self-alignment process with a furnace annealing was applied to the fabrication of heterostructure FETs. Maximum transconductance of 350 mS/mm and the K-value of 430 mA/V2 mm were obtained for the HMT structure (L g=0.7 µm) at room temperature. An intentionally doped channel structure was also studied. An extremely high transconductance of 440 mS/mm and an extremely high K-value of 520 mA/V2 mm were obtained for this structure, suggesting that the performances of HEMTs mainly depend on the capacitance between the gate electrode and the confinedelectron gas.