Quantized conductance and bend resistance in an asymmetric Si/SiGe cross junction

Ballistic electron transport, namely quantized conductance, bend resistance, and its polarity-dependent breakdown, is studied in an asymmetric nanoscale cross junction prepared from a high-mobility Si/SiGe heterostructure. The cross junction is composed of four orthogonal leads which merge into two wide and two narrow quantum point contacts (QPCs). For a wide–narrow combination of leads the two-terminal differential conductance as a function of finite DC bias voltage reveals oscillations and half-plateaus characteristic for quantized conductance. In four-terminal bend resistance configuration with current injection into orthogonal leads negative bend voltage develops between the probing leads. Above a given current threshold the negative bend resistance breaks down just in that bias current polarity where electrons enter the cross region from the narrow QPC. This breakdown is attributed to phonon emission by hot electrons.