Antimony-based quaternary alloys for high-speed low-power electronic devices

Abstract

Heterojunction bipolar transistors using In/sub z/Ga/sub 1-z/Sb for the base and In/sub x/Al/sub 1-x/As/sub y/Sb/sub 1-y/ alloys for the collector and emitter have been explored. Modeling of the DC current-voltage characteristics indicate that current gain in excess of 500 may be obtained. The calculations show that the gain is a function of the base-collector conduction band offset. Molecular beam epitaxy (MBE) procedures for growing suitable alloys with a 6.2 /spl Aring/ lattice constant are under development. Double crystal X-ray diffraction, photoluminescence, Hall effect, and atomic force microscopy have been used to determine the quality of the materials grown. To minimize stress-induced defects, the In/sub x/Al/sub 1-x/As/sub y/Sb/sub 1-y/ alloys were grown on undoped GaSb substrates with an AlSb buffer layer. The photoluminescence data indicate that good quality In/sub x/Al/sub 1-x/As/sub y/Sb/sub 1-y/ (x=0.52 and y=0.3) with a band gap near 1 eV, is obtained using growth temperatures between 350 and 400/spl deg/C. Superior surface morphology is also found for growths in this temperature range. Te has been used to dope In/sub x/Al/sub 1-x/As/sub y/Sb/sub 1-y/ n-type in the 10/sup 17/ cm/sup -3/ range. Good diode characteristics with an ideality factor of 1.1 have been obtained for In/sub x/Al/sub 1-x/As/sub y/Sb/sub 1-y/ p-n junctions grown using Te for the n-type dopant and Be for the p-type.