AlGaAs/GaAs HBTs for 10-Gb/s ICs using a new base ohmic contact fabrication process

• Published in: IEEE transactions on electron devices Vol. 40; no. 1; pp. 25 - 31
• Main Authors: Kusano, C., Masuda, H., Mochizuki, K., Ishikawa, Y., Kawata, M., Mitani, K., Miyazaki, M.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-01-1993; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Capacitance; Conductivity; Cutoff frequency; Electrodes; Electronics; Exact sciences and technology; Gallium arsenide; Gold alloys; Heterojunction bipolar transistors; Ohmic contacts; Performance analysis; Performance gain; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transistors; Analog circuit; Ohmic contact; Circuit design; Computer simulation; Performance characteristic; Aluminium Gallium Arsenides Mixed; Theoretical study; Amplifier; Cut off frequency; Gallium Arsenides; Microelectronic fabrication; Integrated circuit; Heterojunction transistor; High frequency; Performance
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/16.249419

A new basic ohmic contact technology for AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is presented. The effect of the device parameters on the high-frequency performance of HBT ICs for 10-Gb/s systems is analyzed, and it is shown that, at a cutoff frequency (f/sub T/) of 40 GHz or more, reducing base resistance or collector capacitance is more effective than increasing f/sub T/ for obtaining high-frequency performance. A process is developed for fabricating base electrodes with a very low ohmic contact resistivity, approximately 10/sup -7/ Omega -cm/sup 2/, by using a AuZn/Mo/Au alloy, which provides the required high performance. Self-aligned AlGaAs/GaAs HBTs, with a 2.5- mu m*5- mu m emitter, using a AuZn/Mo/Au alloy base metal and an undoped GaAs collector, are shown to have an f/sub T/ and a maximum oscillation frequency of about 45 and 70 GHz, respectively, at 3.5 mA. An AGC amplifier with a 20-dB gain and a bandwidth of 13.7 GHz demonstrates stable performance.< >