SiGe diffusion barriers for P-doped Si/SiGe resonant interband tunnel diodes

Si/SiGe resonant interband tunnel diodes (RITD) employing δ-doping spikes of P and B that demonstrate negative differential resistance (NDR) at room temperature are presented. Thin SiGe layers sandwiching the B δ-doping spike used to suppress B out-diffusion are discussed. Three structures were investigated in this study. Structure A, which employed a symmetrical 1 nm Si /4 nm Si_0.6Ge_0.4/1 nm Si (1/4/1) spacer, showed a peak-to-valley current ratio (PVCR) of 2.7 after 1 minute annealing at 725°C. Structure B with an asymmetrical 0 nm Si/4 nm Si_0.6Ge_0.4/2 nm Si (0/4/2) spacer configuration showed a PVCR of 3.2 after 1 minute annealing at 800°C. Structure C, which is the same as Structure B, except that a 1 nm Si_0.6Ge_0.4 cladding layer was grown below the B δ-layer, further improved PVCR to 3.6 after 1 minute annealing at 825°C. Results clearly show that, by introducing SiGe layers to clad the B delta-doping layer, the B diffusion is suppressed during the post growth annealing, which raises the thermal budget. A higher RTA temperature appears to be more effective in eliminating defects and results in a lower valley current and higher PVCR.