Charge trapping in quantum dot memory devices with different dot densities

The memory characteristics of electrically driven quantum dot (QD) memory devices with different dot densities were investigated by capacitance-voltage (C-V) and current-voltage (I-V) measurements at 100 K. The dots which were embedded in the GaAs quantum well were charged by the electrons from the two-dimensional electron gas at positive gate bias. On cyclically sweeping the gate bias, a clockwise hysteresis loop is observed in the capacitance and conductance trace. The number of trapped electrons was found to decrease slightly as the density of the dots increases from 1.2 to 3 × 10 ⁹ dots cm^-2. Our study reveals that inter-dot tunnelling coupled with Coulombic interaction between the dots and the charged traps in the plane containing the QDs was found to significantly affect the charge trapping ability of the QDs.