A novel route to achieve two dimensional (2D) carrier confinement in a wedge-shaped polar semiconductor structure

A novel route to achieve two dimensional (2D) carrier confinement in a wedge-shaped wall structure made of a polar semiconductor has been demonstrated theoretically. Tapering of the wall along the direction of the spontaneous polarization leads to the development of charges of equal polarity on the two inclined facades of the wall. Negative/positive polarization charges on the facades can push the electrons/holes inward for an n-/p-type material leading to the formation of 2D electron/hole gas at the central plane and depletion regions at the outer edges of the wall. Schrodinger and Poisson equations are solved self-consistently to obtain the potential and charge density distribution in n-type GaN nanowalls, tapered along c-axis by different angles. Carrier mobility in this 2D carrier gas is estimated to be significantly higher than that of bulk. A recent experimental finding indeed shows a very high electron mobility in wedge-shaped GaN nanowall networks. Properties of high mobility and the vertical orientation of the 2D confinement can be exploited in fabricating highly conducting transparent interconnects and high mobility field effect transistors, which can lead to a large-scale integration of 2D devices in future.
S. Deb et al. Sci Rep 6, 26429 (2016)