Investigation of High-Barrier-Gate and Multiple-Channel Structure Heterojunction Field-Effect Transistors

• Main Authors: Yung-Hsin Shie, 薛永鑫
• Other Authors: Wen-Chau Liu
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/89437700956749860677

碩士 === 國立成功大學 === 電機工程學系 === 87 === A high-barrier-gate and multiple-channel structure heterojunction field-effect transistor has been successfully fabricated and demonstrated. A very thin and heavily doped p+-GaInP layer is introduced to enhance high gate turn-on and breakdown voltage and reduce the gate leakage current. The multiple-channel is employed to improve the output current drivability and average transconductance. In addition, a metal-semiconductor field-effect transistor (MESFET) with a multiple-channel has also been fabricated for comparison. Theoretical calculations indicated that the triple-step doped channel has larger barrier height and flatter transconductance among single-step, double-step and triple-step doped channel FET. On the other hand, the influence of p+-GaInP layer has also been examined. Decreasing the p+-GaInP doping density increases the transconductance, which is desirable in logic applications. Decreasing the thickness of p+-GaInP layer increases the transconductance, too. Experimentally, the high gate turn-on voltage Von of 1.6 V and breakdown voltage BVgd of 40 V and the very low gate leakage current of 400 uA/mm are obtained for the studied device. The measured current gain cut-off frequency ft and the maximum oscillation frequency fmax for a 1×100 (um2) gate device are 17 GHz and 33 GHz, respectively. The high breakdown characteristics and the high-frequency performance of the high-barrier-gate and multiple-channel structure HFET are superior to those (BVgd= 25.2 V, ft= 15 GHz and fmax= 26 GHz) of the MESFET. Based on the experimental results, the studied devices show good potential in high-power and large input signal circuit applications.