Thermal Resistance and Electronic Characteristics for High Electron Mobility Transistors Grown on Si and GaAs Substrates by Metal-Organic Chemical Vapor Deposition

Abstract

We report dc and microwave characteristics of 0.8 µm gate length GaAs/AlGaAs high electron mobility transistors (HEMTs) grown on Si substrates by metal-organic chemical vapor deposition (MOCVD) and demonstrate direct evaluation of thermal resistance for these HEMTs on Si for the first time. A maximum transconductance of 330 mS/mm is obtained, which is almost the same as that for HEMT/GaAs fabricated simultaneously. From microwave S-parameter measurements, a current gain cutoff frequency (fT) of 9.8 GHz is obtained for the HEMTs on Si, which is about 20% lower than that for HEMT/GaAs, because of the larger parasitic capacitances for HEMT/Si mainly caused by the device-process-related factors. Thermal resistance evaluation of these HEMTs utilizing the gate Schottky junction has revealed that thermal resistance for HEMT/Si is twice as small as that for HEMT/GaAs, namely 36±5 deg/W and 57±5 deg/W, respectively. From these results, it is shown that GaAs on Si is applicable to high-speed devices and very effective in improving the performances of CaAs ICs which are fairly influenced by the power dissipation.