We will present nano-scale correlation of structural, electronic and optical properties of GaN-based power devices by cathodoluminescence directly performed in a scanning transmission electron microscope. The two-dimensional electron gas (2DEG) of a lateral AlGaN/GaN field-effect transistor has been investigated directly probing the local origin of the 2DEG by its spectral luminescence fingerprint. This characteristic 2DEG luminescence is locally observed nanometers inside the GaN - close to the GaN/AlN/AlGaN interface. Furthermore, a lateral p-n+ superjunction will be presented, where excitonic and donor-acceptor transitions directly visualize the space charge region evidencing the exciton dissociation in the built-in electric field.
KEYWORDS: Gallium nitride, Temperature metrology, Luminescence, Diffusion, Visualization, Spatial resolution, Scanning electron microscopy, Line scan image sensors, Excitons, Electron microscopes
A lateral p+n GaN junction with a 10 µm drift layer has been characterized by combined Cathodoluminescence (CL) and Electron-Beam-Induced Current (EBIC) measurements performed at different temperatures. A vertical CL linescan across the pn-junction shows the evolution of luminescence in growth direction. The distinct changes of local emission in the space charge region are correlated with temperature dependent EBIC profiles. In particular in the drift zone, a mono-exponential behavior with a large characteristic length was observed. These profiles are correlated to the calculated band profiles for quantifying the evolution of electrical fields in the space charge region and drift zone.
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