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InP/InGaAs heterojunction bipolar transistors and field-effect transistors grown by gas -source molecular beam epitaxy

Posted on:2000-10-23Degree:Ph.DType:Thesis
University:University of Illinois at Urbana-ChampaignCandidate:Kuo, Hao-chungFull Text:PDF
GTID:2468390014466073Subject:Electrical engineering
Abstract/Summary:
Both InP/InGaAs heterojunction bipolar transistor (HBT) and heterojunction field effect transistor (HFET) technologies have demonstrated excellent device cutoff frequency and record-setting circuit performance. This thesis is on the development of gas-source molecular beam epitaxy (GSMBE) material growth and device fabrication technologies for InP/InGaAs BiFET.;A systematic investigation of the Schottky characteristics of metal/Ga 0.2In0.8P/InP structures has shown that barrier heights of 0.6--0.7 eV can be achieved for Schottky junctions formed on Ga 0.2In0.8P/InP. No degradation in the Schottky characteristics is observed at temperatures as high as 250°C. InP/InGaAs doped-channel HFETs with Ga0.2In0.8P Schottky barrier enhancement layers (SBEL) were grown and fabricated. The 0.15-mum-gate-length devices show excellent dc and RF performance. The extrinsic dc transconductance of the HFET is 716 mS/mm, and the fT and the fmax are values of 171 and 186 GHz, respectively. These fT and fmax are also comparable to those of other works of InGaAs channel HEMTs with the same gate length.;High material quality C-doped InGaAs layers and Npn InP/InGaAs HBTs have been successfully grown by GSMBE. For standard HBT devices employing InGaAs contacting layers, the excellent device performance validates the GSMEBE-grown material quality. For dc performance, these devices showed good Gummel characteristics with nc = 1.02--1.08 and nb = 1.17--1.2. The gain (beta) variation for different devices was found to be proportional to the square of the base sheet resistance (Rsb2) which indicates the minority electron lifetime in the base region is limited by diffusive base and Auger recombination. For high frequency measurements of 3 X 10 mum2 emitter area devices (700-A base /4000-A collector), the peak fT of 108 GHz was observed at an Ic of 21 mA with a corresponding fmax of 128 GHz. These values are comparable to those for C-doped base devices grown by metalorganic molecular beam epitaxy (MOMBE) and similar structures grown using Be as the p-type dopant. To further improve high frequency performance, standard HBTs (500-A base /3000-A collector) with graded emitter contact composed of In0.75Ga0.25As (250-A)/graded-InGaAs (500-A)/In 0.53Ga0.47As (750-A) were grown.;Finally, the thermal degradation of heavily C-doped InGaAs and its effects on dc properties of InGaAs/InP HBTs have been studied. The degradation of the junction properties and current gain-base sheet resistance ratio can be attributed to the formation of C precipitates. These findings are important for improving the reliability of C-doped InP/InGaAs HBTs. (Abstract shortened by UMI.).
Keywords/Search Tags:Inp/ingaas, Molecular beam, Heterojunction, Grown, C-doped, Hbts
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