Low temperature performance of pure ternary InAlAs-InGaAs-InAlAs double heterojunction bipolar microwave transistors

Abstract

All ternary InAlAs-InGaAs-InAlAs Double Heterojunction Bipolar Transistors (DHBTs) are experimentally demonstrated to operate down to liquid nitrogen temperature with a breakdown (BVceo) voltage of 7.6 V at 0.05 kA/cm2 which is achieved despite collector thickness of only 2000 Å and heavy dipole doping of 4 × 1018 cm−3. The wafers were Molecular Beam Epitaxy grown without resorting to any complex growth techniques such as CHIRP (coherent heterointerfaces for reflection and penetration) superlattice or quaternary alloys for grading. Gummel plot shows a finite current gain varying from 4 to 30, as collector current was varied over six orders of magnitude (from 7 nA to 7 mA), and up to a current density of 50 kA/cm2 at 77 K. The resulted high breakdown voltage and relatively better current gain stability over temperature in comparison with SiGe make these microwave devices of relaxed geometry (1 × 15) µm2, fabricated using simple optical lithography which are suitable for many low temperature applications such as high-sensitivity cooled sensors and detectors and cryogenic low-noise amplifiers (LNAs) offering a competitive alternative to deep-submicron SiGe technology.