Spatial distribution of two-dimensional electron gas in a ZnO / Mg 0.2 Zn 0.8 O heterostructure probed with a conducting polymer Schottky contact

A ZnO / Mg 0.2 Zn 0.8 O heterostructure was characterized at T = 2 K through capacitance measurements with using a conducting polymer, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), as a Schottky contact. The Nyquist diagram, which is the trajectory curve of the complex impedance vector, appeared to be an excellent semicircular shape, implying that the PEDOT : PSS / ZnO / Mg 0.2 Zn 0.8 O junction can be described with an equivalent single R C parallel circuit. Capacitance-voltage characteristics elucidate the existence of a two-dimensional electron gas, where 10 19 cm − 3 electrons are confined within 5 nm at the ZnO / Mg 0.2 Zn 0.8 O heterointerface.