III-Nitride-based junction devices round contacts: effect of semiconductor film geometry and characteristics on the capacitance and conductance measurements

A theoretical model was developed, which allows simulating the capacitance (C) and conductance/frequency (G/f) profiles as a function of operation frequencies for a round Schottky diode, and in terms of a transfer length concept, L_T(jω), which depends on the electrical characteristics of AlGaN:Si semiconductor film, dimensions and structure Schottky diode. The (C) and (G/f) measurements were performed by applying a small electrical signal far away and parallel to the planar structure of junction device, due to the impossibility of accessing perpendicularly path, since the AlGaN:Si semiconductor film was deposited over a substrate of high electrical resistivity, just as it happens with the III nitrates materials. The (C) and (G/f) profiles were measured for operating frequencies ranging from 3 kHz to 1 MHz. Comparison of experimental measurements and theoretical model were analyzed. It was found that the structure Schottky and electrical characteristics of film plays an important role as a limiting factor in the (C) and (G/f) measurements at media and high operating frequencies.