Electrical Characteristics of AlGaN/GaN Schottky Barrier Diodes with Different Capping Layers

Abstract

We investigated the effects of various capping layers on the device performance of AlGaN/GaN Schottky barrier diodes (SBDs). The electrical characteristics of SBDs containing Ni/Au and Ti/Al/Ni/Au electrodes for the Schottky and Ohmic contacts, respectively, were observed by employing a current-voltage (I-V) measurement system. The I-V measurement results show that the reverse leakage current in the n-GaN capping layer formed on AlGaN/GaN SBD is 6-7 orders higher than those of the SBDs, both with the u-GaN capping layer and without a capping layer. The observed threading dislocation density (TDD) obtained by atomic force microscopy analysis of the different capping layer surfaces revealed that the n-GaN capping layer sample has almost a 3 times higher TDD than that of the samples both with the u-GaN capping layer and without a capping layer. From the proportional relationship between the TDD and leakage current level, threading dislocation can be the dominant path for the leakage current flow in AlGaN/GaN SBDs.