Plasma-induced damage influence on the n -contact properties and device performance of ultraviolet InGaNAlGaN light-emitting diodes

We report on plasma-induced-damage influence on the n -ohmic contact properties and device performance of ultraviolet InGaNAlGaN light-emitting diodes (LEDs). A significant plasma-power dependence of n -ohmic contacts on electrical properties could be due to the generation of different types of point defects and movement of the surface Fermi level, which were confirmed by photoluminescence and X-ray photoelectron spectroscopy measurement. Unlike the low plasma-power-etched LED, the high plasma-power-etching in the LED results in an increase of the high threshold voltage, series resistance, and reverse leakage current. In addition, the current crowding in the plasma-damaged LEDs occurs even at low injection current of 5 mA, while that for the low plasma-power-etched LED does not happen. These different device characteristics are described and discussed in terms of the resistivity of the GaN and ohmic contacts and the current spreading length (from p - to n-GaN layer).