Inhomogeneous electroluminescence for characterizing lateral transport in semiconductor devices

In multilayer semiconductor devices, carrier transport perpendicular to the growth axis is important for generating uniform current density and minimizing local heating. However, lateral transport within individual layers of the structure can be hindered by fluctuations in layer thickness, alloy composition, and other defects. Impediments to lateral transport can be analyzed by imaging electroluminescence as a function of temperature and injection density. Inhomogeneity in the emission pattern distinguishes preferred current channels from less favorable pathways through the device. The temperature dependence of the nonuniformity can be used to gauge the localization energy and the dependence on injection current can be used to estimate the density of laterally localized states. In this report, we use an InGaN/GaN diode to demonstrate this characterization technique. We find that lateral transport in this device is thermally activated with an activation energy of 37 meV. Our analysis also shows that the density of localized states in the lower energy regions is relatively small, saturating at a current density of approximately 0.5 mA/cm(2).