Fabrication of CaF2/Si/CaF2 resonant-tunneling diodes by B-surfactant enhanced epitaxy of Si quantum-well layers

Double-barrier CaF₂/Si/CaF₂ resonant-tunneling diodes (RTDs) were fabricated by utilizing a new boron (B) surfactant-enhanced solid-phase epitaxy (SPE) technique for the critical growth of the Si quantum-well films on CaF₂/Si(111) substrates. This technique consists of the room temperature deposition of an amorphous Si film, the subsequent deposition of one monolayer of B atoms, and annealing to about 635°C. This resulted in continuous and smooth epitaxial Si layers on CaF₂ with a sharp B-induced (√3×√3 )R30° surface reconstruction. At 77 K the RTDs exhibited stable N-type I-V characteristics with negative differential resistance (NDR) with 2-7 orders of magnitude higher peak currents and much lower peak voltages than in earlier results.