Investigation of generation-recombination centres of Au/n-GaAs Schottky diodes with InAs self-assembled quantum dots

Capacitance and reverse current-voltage measurements have been performed as a function of temperature on Au/n-GaAs Schottky diodes with InAs quantum dots (QDs) embedded between two GaAs spacers. The spacers were either doped or undoped containing a QD layer equivalent to 3 monolayer (ML) QD coverage. In the investigated temperature range of 77-350 K and for all the diodes measured, the apparent free electron concentration close to the QDs layer is lower compared to the concentration at the interface between GaAs doped buffer layer and GaAs n+-substrate, showing that the QDs induce more traps than those created at a conventional interface. Theoretical fitting of the capacitance-voltage characteristics yields the values of the energy level, the sheet concentration and the dispersion of the distribution of the confined states induced by the InAs quantum dots, which is higher for the diode with doped GaAs spacers than for the diode with undoped spacers. The effective activation energies of the traps, obtained from the effective generation lifetime calculated from reverse voltage current, agree well with the results obtained from the theoretical fitting.