Investigation of GeSn/Ge quantum dots’ optical transitions for integrated optics on Si substrate

Abstract

The effects of self-organized GeSn/Ge quantum dot’s size and shape on the direct band gap interband emission energy, oscillator strength and radiative lifetime are evaluated. The electron’s and the hole’s confined energies and their corresponding wave function are driven by solving the 3D Schrodinger equation in Cartesian coordinates using the finite elements method. Dome and pyramidal shaped quantum dots are considered within practically exploitable size and aspect ratio that allows direct band gap transition energies. It is found that bigger quantum dots with higher aspect ratio are likely to have higher oscillator strength and longer radiative lifetime. For smaller aspect ratio, the emission energy, oscillator strength and radiative lifetime are found to be very sensitive to the quantum dot’s size and shape. These results demonstrate that this quantum dot QD system could be very interesting for CMOS compatible light emitters and detectors operating in the mid-IR range.