High-gain, low offset voltage, and zero potential spike by InGaP/GaAs δ-doped single heterojunction bipolar transistor (δ-SHBT)

Abstract

We report on fabrication, characterization, and comparison of InGaP/GaAs single heterojunction bipolar transistors (SHBT's) and heterostructure-emitter bipolar transistors (HEBT's). The SHBT with a /spl delta/-doped sheet located at the E-B heterointerface (/spl delta/-SHBT) exhibits a common-emitter current gain as high as 410 and an extremely low offset voltage of 55 mV. Even though at the small collector current density of 1/spl times/10/sup -3/ A/cm/sup 2/, the current gain is still larger than 20. Theoretical derivations show that the zero potential spike exists near the E-B junction under +1.5 V forward bias. However, an HEBT with a 700-/spl Aring/ narrow energy-gap emitter shows a small current gain and a collector current density due to the charge storage and bulk recombination effect. On the other hand, the increase of the CB capacitance in our /spl delta/-SHBT is very small as compared with conventional HBT's.