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

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 delta-doped sheet located at the E-B heterointerface (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 x 10(-3) A/cm(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 biased. However, an HEBT with a 700-Angstrom narrow energy-gap emitter shoes 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 GB capacitance in our delta SHBT is very small as compared with conventional HBT's.