Atomically controlled formation of strained Si_1-xGe _x/Si quantum heterostructure for room-temperature resonant tunneling diode

Atomically controlled formation of strained Si_1-xGe _x/Si quantum heterostructure was investigated in order to improve negative differential conductance (NDC) characteristics of high-Ge-fraction strained Si_1-xGe_x/Si hole resonant tunneling diode with nanometer-order thick strained Si_1-xGe_x and unstrained Si layers. Recently, especially to suppress the roughness generation at heterointerfaces for higher Ge fraction, Si barriers were deposited using Si₂H₆ reaction at a lower temperature of 400 ^°C instead of SiH₄ reaction at 500 ^°C after the Si_0.42Ge_0.58 growth. NDC characteristics show that difference between peak and valley currents is effectively enhanced at 11-295 K by using Si₂H₆ at 400 ^°C, compared with that using SiH₄ at 500 ^°C. Thermionic-emission dominant characteristics suggests a possibility that introduction of larger barrier height enhances the NDC at room temperature by suppression of thermionic-emission current. In this paper, based on our results, advanced epitaxial growth process of RTDs with atomically controlled Si/strained Si _1-xGe_x heterostructures on Si(100) are reviewed.