Admittance spectroscopy of GeSi-based quantum dot systems: Experiment and theory

A combined experimental and theoretical study is carried out in examining the important features of the admittance spectroscopy (AS) of self-assembled GeSi quantum dot (QD) systems. In the experimental component of the study, we measure the dependence of the AS on size of the GeSi QDs. From such measurements, we determine the emission rate and activation energy of the carriers in different QDs. Theoretically, we develop a simple approach to understand and reproduce those observed experimentally. It is found both experimentally and theoretically that with increasing size of the QDs, the peak of the AS shifts to higher-temperature regime, the activation energy of the carriers increases and the emission rate of the system decreases. These interesting phenomena can be well explained by the fact that in GeSi-based QD systems, the AS is mainly induced by zero-dimensional to three-dimensional transition through hole interactions with acoustic phonons via deformation potential coupling.