Morphology-Driven Stark Shift Switching in Ge/Si Type-II Heterointerfaces

Abstract

Morphology-related anomaly was found in the photoluminescence (PL) of Ge/Si type-II double heterostructures with varying Ge coverage. PL Stokes shifts of 2-D Ge wetting layers functioning as a quantum well for holes switched from negative to positive under electric field as Ge coverage crossed 3.7 monolayers, which correlates well with the onset of Stranski-Krastanow growth mode transition. The origin of such shift polarity switch is discussed in terms of the linear Stark effect in an asymmetric confinement potential developing due to 3-D Ge islands.