ABRUPT DELTA-LIKE DOPING IN SI AND SIGE FILMS BY UHV-CVD

A structure and method of forming an abrupt doping profile are described. A perferred embodiment incorporates a substrate 32, a first epitaxial layer 36 of Ge less than the critical thickness and having a P or As concentration greater than 5x10 atoms/cc, and a second epitaxial layer 40 having a change in concentration in its first 40 ANGSTROM from the first layer of greater than 1x10 P atoms/cc. In another preferred embodiment, a layer of SiGe having a Ge content greater than 0.5 may be selectively amorphized and recrystalized with respect to other layers in a layered structure. The invention addresses the problem of forming abrupt phosphorus profiles in Si and SiGe layers or films in semiconductor structures such as CMOS, MODFET's, and HBT's.