Charge storage in GaAs metal insulator semiconductor field effect transistor metal nanodot memory structures

Charging effects in 3–4-nm-diam AuPd nanodots have been investigated by comparing the characteristics of depletion mode delta-doped GaAs metal insulator semiconductor field effect transistor with and without a nanodot floating gate layer. The nanodots were embedded in a 10-nm-thick Al2O3 gate insulator, formed by a self-limiting oxidation process. Charge transfer takes place by tunneling between the channel of the transistor and the nanodots through the Al2O3. In this experiment the total nanodot layer charge could be directly determined using capacitance measurements and compared with the number of nanodots. It was concluded that there was an average of about one excess electron per nanodot. The charging of the nanodots gives rise to a threshold voltage shift in the transistor that can be applied to information storage applications.