Fabrication of high-Ge-fraction strained Si 1−xGe x/Si hole resonant tunneling diode using low-temperature Si 2H 6 reaction for nanometer-order ultrathin Si barriers

Abstract

Low-temperature Si barrier growth with atomically flat heterointerfaces was investigated in order to improve negative differential conductance (NDC) characteristics of high-Ge-fraction strained Si 1− x Ge x /Si hole resonant tunneling diode with nanometer-order thick strained Si 1− x Ge x and unstrained Si layers. Especially to suppress the roughness generation at heterointerfaces for higher Ge fraction, Si barriers were deposited using Si 2H 6 reaction at a lower temperature of 400 °C instead of SiH 4 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 Si 2H 6 at 400 °C, compared with that using SiH 4 at 500 °C. Non-thermal leakage current at lower temperatures below 100 K tends to increase with decrease of Si barrier thickness. Additionally, thermionic-emission dominant characteristics at higher temperatures above 100 K suggests a possibility that introduction of larger barrier height (i.e. larger band discontinuity) enhances the NDC at room temperature by suppression of thermionic-emission current.