A small-signal linear equivalent circuit of HEMTs fabricated onGaAs-on-Si wafers |
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Authors: | Goto M Ohta Y Aigo T Moritani A |
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Institution: | Adv. Res. Lab., Nippon Steel Corp., Kanagawa; |
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Abstract: | A new small-signal linear equivalent circuit for high electron mobility transistors (HEMTs) fabricated on GaAs-on-Si wafers, HEMTs-on-Si, has been proposed. The new equivalent circuit describes the microwave characteristics of HEMTs-on-Si much better than the conventional metal-semiconductor field-effect transistor (MESFET) equivalent circuit does. Influences of the pads, the GaAs-Si interface, and the Si substrate on the microwave characteristics are included in the circuit. It also has a great advantage in that it can separately analyze the intrinsic device characteristics and influences of Si substrate and GaAs-Si interface. Analyzes using the new equivalent circuit show that the crucial problem of HEMTs-on-Si is the larger values of the pad capacitances and the drain-source capacitances than those of HEMTs fabricated on GaAs bulk wafers, HEMTs-on-GaAs, and that the substrate resistivity is not an important factor for microwave performances of HEMTs-on-Si. The microwave performance was improved by the reduction of the pad capacitances |
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