Temperature dependence of current-voltage characteristics in highly doped Ag/p-GaN/In Schottky diodes

Abstract

To obtain detailed information about the conduction process of the Ag/p-GaN Schottky diodes (SDs) fabricated by us, we measured the I-V characteristics over the temperature range of 80–360 K by the steps of 20 K. The slope of the linear portion of the forward bias I-V plot and nkT=E0 of the device remained almost unchanged as independent of temperature with an average of 25.71±0.90 V−1 and 41.44±1.38 meV, respectively. Therefore, it can be said that the experimental I-V data quite well obey the field emission model rather than the thermionic emission or thermionic field emission model. The study is a very good experimental example for the FE model. Furthermore, the reverse bias saturation current ranges from 8.34×10−8 A at 80 K to 2.10×10−7 A at 360 K, indicating that the charge transport mechanism in the Ag/p-GaN SD is tunneling due to the weak temperature dependence of the saturation current. The possible origin of high experimental characteristic tunneling energy of E00=39 meV, which is ten times larger than possible theoretical value of 3.89 meV, is attributed to the accumulation of a large amount of defect states near the GaN surface or to the deep level defect band induced by high doping or to any mechanism which enhances the electric field and the state density at the semiconductor surface.