Epitaxially grown base transistor for high-speed operation

We developed a transistor with a very thin base to improve the speed of the intrinsic bipolar transistor. The epitaxially grown base transistor, or EBT, consists of an in-situ boron-doped epitaxial base layer that is photochemically grown, Photoepitaxy, with a low growth temperature of about 650°C, enables us to fabricate a very thin heavily doped layer. Our EBT has a base 65 nm thick and a peak boron concentration of 1 × 10
¹⁹
/cm
³
. Compared with high-speed bipolar transistors reported to date, EBT's have half the base width and ten times the peak boron concentration. The maximum current gain was about 500. Despite the very thin base, the Early voltage was about 70 V because of the high boron concentration. The EBT is potentially capable of very high-speed operation if combined with a structure that minimizes parasitic capacitance.