Theory of junction between two-dimensional electron gas and p-type semiconductor

The authors develop a theory of the junction between a two-dimensional electron gas and a three-dimensional p-type semiconductor contact. The cut-in voltage of such a junction depends on the density of the 2-D electron gas. Hence, at low currents, the device current varies exponentially with the 2-D gas density. The unique features of such junctions include a very small effective cross section (equal to the product of the thickness of the 2-D gas and the device width) and, hence, a small junction capacitance and a small device current at large current densities. Using a conformal mapping technique, the authors calculate potential and field distributions and find the differential device capacitance as a function of bias. They then calculate the output device characteristics for different gate voltages. The results of a 2-D self-consistent Monte Carlo simulation for such a structure are presented. This simulation clearly shows that electrons and holes are localized in the vicinity of the 2-D electron gas even at high drain biases