Emission of Electrons in InAs Quantum Dot Memory Devices Studied by Drain-Current Deep Level Transient Spectroscopy

We studied emission process of electrons in InAs quantum dot (QD) memory devices by means of drain-current deep level transient spectroscopy (DLTS). The GaAs narrow-wire field effect transistors with a few InAs QDs above the channel were fabricated by selective-area metal organic vapor-phase epitaxy. The drain current, measured by sweeping the gate voltage forward and backward, exhibited clear clock-wise hysteresis due to charging of electrons into the states induced by InAs QDs with a threshold voltage shift (DeltaVth) of 30 mV at 20 K. Peaks representing three kinds of electron traps concerning InAs QDs were observed in the DLTS spectra. These peaks exhibited different dependences on the applied gate pulsed voltage during the DLTS measurement. In comparison with the temperature dependence of DeltaVth, we found that our memory operation was attributed to one localized state introduced by InAs QDs.