Hole tunnelling properties in resonant tunnelling diodes with Si/strained Si0.8Ge0.2 heterostructures grown on Si(1 0 0) by low-temperature ultraclean LPCVD

Abstract

Hole resonant tunnelling diodes (RTDs) with Si/strained Si1–xGex heterostructures epitaxially grown on Si(1 0 0) were fabricated, and sharp current peaks have been reproducibly observed. From the quantum well width dependence of the current–voltage characteristics, at the peak voltage, heavy holes in the accumulation region resonantly tunnel through the estimated resonant states of a light hole and a heavy hole in a Si1–xGex quantum well. The top contact and mesa area dependence of the peak current shows that the tunnel current only flows under a top contact electrode, i.e. the leakage current at the sidewall is negligibly small. The resonant tunnelling current density reaches as high as 3.6 kA cm−2 at 0.19 V with 2 nm thick barriers. Moreover, the introduction of higher Ge fraction effectively suppresses the increase of the valley current and enables negative differential conductance at higher operation temperature.