Doping effects and effective capacitance-voltage characteristics of metal-wrapped semiconductor (aluminum-gallium nitride) nanowire radii

Abstract

Metal-wrapped semiconductor nanowire is a cylindrical junction Schottky diode whose detailed electrostatics and characteristics are studied for Aluminum-Gallium Nitride (Al-GaN).  Two crucial principles have been used for the method of analyses: Poisson’s equation for the voltage in the depletion region and the exact solution of the metal-semiconductor junction state equation for effective barrier height. The smaller the radius of the semiconducting nanowire the highly depleted it is compared to higher radii even with small doping density. The depletion width increases inversely with doping concentration. Regardless of the doping concentration, nanowires of higher radii appear to have lesser depletion, hence a greater conducting core radius of the vertical device. For a 100 nm radius, the depletion width decreases from approximately 38.112 nm to 3.113 nm at 300 K as doping density increases from 10¹⁶ cm^-3 to 2 × 10¹⁸ cm^-3. It can be seen that the smaller radius of nanowire is expected to be completely depleted, an excellent result that matches with experiments. This obviously permits tunneling of electrons in highly doped semiconducting nanowires and perhaps leads to degeneracy of the semiconducting nanowire. The effective capacitance of the junction is non-linear in both forward and reverse bias voltage application and also a function of the wrapped semiconductor radii.