DOPING OF SI THIN-FILMS BY LOW-TEMPERATURE MOLECULAR-BEAM EPITAXY

Two-dimensional doping sheets (''delta doping'') are integral parts of many novel semiconductor device concepts. Deep submicron design rules require junction depths significantly below 100 nm. This level of control is difficult to achieve with ion implantation. We discuss the application of thermal, coevaporative doping with Sb and elemental B during Si molecular beam epitaxy at growth temperatures below almost-equal-to 300-degrees-C to this problem. We show that it is possible to create structures with very high doping levels, yet with very sharp doping transitions. Delta-doping spikes with a full width at half maximum of < 2.7 nm and < 4.0 nm have been obtained by secondary-ion mass spectrometry for Sb and B, respectively, with corresponding up-slopes of 2.5 and 0.94 nm/decade. Homogeneously doped films show full activation up to N(Sb) almost-equal-to 6 X 10(20) cm-3 and N(B) > 1 X 10(21) cm-3. Mobilities agree with bulk values at corresponding concentrations. Mesa-isolated pn junctions exhibit ideality factors of 1.05.