Concentration Effects on n-GaN Schottky Diode Current-Voltage (i-v) Characteristics
We focus on the epi layer carrier concentration variation effects to improve the current – voltage (I-V) characteristics of an n-GaN schottky diode. The carrier concentration of 1×10 15cm-3, 1×1016 cm−3, 1×1017 cm−3 were employed. The simulated current was obtained by forward biasing the device of up to 2Volt at room temperature using Pt electrode. The study was conducted by using Atlas/Blaze using various models such as Consrh (Concentration Dependent Shockley Read Hall), Cvt (Lombardi Model), Fermi (Fermi Dirac), Bgn (Bandgap Narrowing), Conmob (Concentration Dependent Mobility), Auger (Auger). We found that as the concentration increases the value of forward current also increase linearly when biased at maximum of 2 volts. The reverse bias characteristics at the same concentration of the simulated diode up to 100Volt were also determined. We found that at low carrier concentration the reverse leakage current is minimum and breakdown voltage is maximum. As the carrier concentration increases there is a linear relationship between reverse leakage current and epi layer doping carrier concentration. By analyzing the forward and reverse characteristics we conclude that in forward bias for low carrier concentration the diode shows schottky rectifying behavior while for higher carrier concentration the diode shows ohmic behavior. For higher carrier concentration there is a linear relationship between carrier concentration (n) and forward current. The reverse leakage current is minimum approaching an ideal value at n≤1×1015cm-3 and breakdown voltage is maximum at these values of concentration. Increasing the concentration from n≤1×1015cm-3 the value of reverse leakage current is approaching to the maximum value as a result breakdown voltage decreases. We conclude that for n-GaN schottky diode the ideal schottky rectifying behavior of I-V characteristics is obtained at carrier concentration of n≤ 1×1015cm-3 for the simulated diodes at different carrier concentration.
A.K. Arof and S.A. Hashim Ali
T. Munir et al., "Concentration Effects on n-GaN Schottky Diode Current-Voltage (i-v) Characteristics", Materials Science Forum, Vol. 517, pp. 159-164, 2006