High Current Density Trench CAVET on Bulk GaN Substrates with Low-Temperature GaN Suppressing Mg Diffusion

We report that, for the first time, a low-temperature GaN (LT-GaN) layer prepared by metal-organic chemical vapor deposition (MOCVD) regrowth was used as a Mg stopping layer (MSL) for a GaN trench current-aperture vertical electron transistor (CAVET) with p-GaN as a carrier blocking layer (CBL). Inserting LT-GaN on top of the p-GaN effectively suppresses Mg out-diffusion into the regrown AlGaN/GaN channel, contributing to the high current capability of GaN vertical devices with a p-GaN CBL. With different MOCVD growth conditions, MSLs inserted in trench CAVETs were comprehensively investigated for the influence of MSL regrowth temperature and thickness on device performance. With the best on-state current performance obtained in this study, the trench CAVET with a 100 nm thick MSL regrown at 750 degrees C shows a high drain current of 3.2 kA/cm(2) and a low on-state resistance of 1.2 m omega center dot cm(2). The secondary ion mass spectrometry (SIMS) depth profiles show that the trench CAVET with the 100 nm thick MSL regrown at 750 degrees C has a dramatically decreased Mg diffusion decay rate (similar to 39 nm/decade) in AlGaN/GaN channel, compared to that of the CAVET without a MSL (similar to 104 nm/decade). In developing GaN vertical devices embedded with a Mg-doped p-type layer, the LT-GaN as the MSL demonstrates a promising approach to effectively isolate Mg from the subsequently grown layers.