Nitrogen atomic-layer (N AL) doping effects upon hole tunneling characteristics of double 4 nm-thick Si barriers in the strained Si1-xGex/Si(100) hole resonant tunneling diode (RTD) were investigated. At a Si cap layer on Si1-xGex(100) (x = 0.2 and 0.4) formed at 500 degrees C, it was found that NH3 reaction was drastically enhanced at 500 C especially at the Si cap layer thickness less than 0.5 nm, and the fact indicates a possibility of significant intermixing at the Si/Si1-xGex heterointerface. From current-voltage characteristics of the RTDs, drastic current suppression by N AL doping in the Si barriers can be observed with typical degree of current suppression as high as 10(3)-10(5) at -10 mV. Moreover, it was found that N AL doping influences, not only upon such current suppression, but slightly upon negative differential conductance characteristics. (c) 2013 Elsevier B.V. All rights reserved.