190-GHz f/sub T/, 130-GHz f/sub max/ SiGe HBTs with heavily doped base formed by HCl-free selective epitaxy

A heavily-boron-doped SiGe base was formed by HCl-free selective epitaxial growth using LPCVD. This HCl-free growth enabled us to obtain high growth rate at low temperature and to suppress surface roughening of heavily-boron-doped SiGe. HBTs were fabricated with base regions with high boron concentration, i.e. 2.4 /spl times/ 10/sup 20/ cm/sup -3/. An accurately and appropriately designed boron profile produced HBTs with f/sub T/ of 190 and f/sub max/ of 130 GHz. By modifying the impurity profiles in the intrinsic region, f/sub T/ was increased above 200 GHz. These high-performance HBTs were implemented in a multiplexer and a demultiplexer, and resulted in faster than 50-Gb/s performance.