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 × 10¹⁹/cm³. 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.