Charge accumulation in Ge quantum dots in a GaAs/ZnSe/QD-Ge/ZnSe/Ge floating gate transistor structure

A GaAs/ZnSe/QD-Ge/ZnSe/Ge germanium-quantum-dot floating-gate transistor structure is obtained and investigated by molecular beam epitaxy. It has been shown that a positive change in the channel current is observed upon light illumination with wavelengths longer than 0.5 μm and a negative change is observed for shorter wavelengths, which is associated with charging of quantum dots. Measurements of relaxation curves after switching off the illumination show that the decay of the current lasts for from tens of seconds to several hours, depending on the temperature of the sample. The changes in the channel current and relaxation curves indicated above are explained based on the existence of three types of transitions in quantum dots upon radiation absorption with allowance made for the variation of the channel state near the heteroboundary from depletion to inversion as a result of charge accumulation in quantum dots.