Point-defect associated thermionic hole emissions from p-type Si/Si 1 ? x Ge x /Si quantum well structures

Abstract

The thermionic hole emissions from a p-type Si0.67Ge0.33 quantum well with a width of 7 nm and a point defect were investigated using deep level transient spectroscopy. An activation energy of 0.22 eV from the quantum well is consistent with the heavy hole level from the bottom of the well. The defect-related band with an energy of 0.30 eV originated from the space charge related to the point defect in the vicinity of the quantum well heterostructure. The origin of the point-defect-related band was confirmed by photoluminescence and the deep level was further clarified by using capacitance-voltage measurements and simulation by introducing a simple model of an interfacial hole trap center. The deep hole trap center apparently disappeared by an annealing effect, indicating that point defects are subject to thermal annealing. The microscopic measurement provides evidence on point defects in the quantum well structure and the thermal annealing also enhances the thermionic hole emission from the quantum well structure.