| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 88 === One way of improving the AlGaAs/GaAs conventional HEMT performance is to use InGaAs as the two-dimensional electron gas channel material instead of GaAs. Because the InGaAs pseudomorphic channel is buried inside the double heterojunction layers, the processing techniques developed for AlGaAs/GaAs conventional HEMTs can be used for pseudomorphic HEMTs without modification.
Gate recess is a important process during the fabrication of PHEMT device. For power applications, a recess opening larger than the gate is necessary to obtain a large BVgd. Our investigations showed that a BVgd as high as 25V can be achieved by simply making a wide recess in the AlGaAs schottcy layer. The wide recess device exhibited a peak gm of 151mS/mm, and a maximum current density of 248mA/mm. The narrow recess device exhibited a lower gate to drain breakdown voltage of 8.7 volts, a peak gm of 173mS/mm, and a maximum current density of 267mA/mm. Based on all experimental results, we find that wide recess device shows good potential in high-power and high-frequency performance.
At last, we have successfully demonstrate the air-bridge technique with electroplating process. The air bridge technique will provides us applications to realize interconnect for MMIC (Monolithic Microwave Integrated Circuits) and high power devices.
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