The effect of carbon incorporation on SiGe heterobipolar transistor performance and process margin

We present the high-frequency characteristics of heterojunction bipolar transistors (HBTs) with SiGe:C base layers grown by molecular beam epitaxy (MBE). We demonstrate peak f/sub T//f/sub max/ values up to 75/65 GHz, and delay times per stage down to 15 ps for ring oscillators with integrated SiGe:C HBTs. The use of epitaxial SiGe:C layers instead of SiGe offers wider latitude in process margin, without affecting dc performance.