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 Si1-xGex/Si hole resonant tunneling diode with nanometer-order thick strained Si1-xGex and unstrained Si layers. 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 degrees C instead of SiH4 reaction at 500 degrees C after the Si0.42Ge0.58 growth. NDC characteristics show that difference between peak and valley currents is effectively enhanced at 11-295 K by using Si2H6 at 400 degrees C, compared with that using SiH4 at 500 degrees 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. (C) 2011 Elsevier Ltd. All rights reserved.