Lateral p-GaN/2DEG junction diodes by selective-area p-GaN trench-filling-regrowth in AlGaN/GaN

This work demonstrates a lateral p-n junction diode formed between the two-dimensional electron gas (2DEG) and the selective-area regrown p-GaN in AlGaN/GaN. Benefiting from the in-plane 2DEG channel, this p-GaN/2DEG diode can directly characterize the current conduction and voltage blocking characteristics of the regrown sidewall p-n junction, which has been regarded as the key building block of future high-voltage GaN power devices. Control samples with planar regrown p-n junctions are first used to optimize the regrowth conditions. The planar junction characteristics show considerable improvement by adding the Mg pre-flow (Cp2Mg) before the p-GaN regrowth, which is attributed to the Mg out-diffusion beyond the regrowth interface. A record high ratio between the Mg concentration and the maximum impurity (C, Si, O) spike at the regrowth interface is demonstrated. Using the optimal regrowth conditions, the fabricated p-GaN/2DEG junction diodes show excellent rectifying behavior with an on/off ratio of over 5 × 107 in both large-area devices and the multi-finger devices with 1 μm-wide finger trenches. A breakdown voltage over 100 V is demonstrated, where the peak electric field is estimated to be at least 2.5 MV/cm at the sidewall junction. These results not only suggest that p-GaN trench-filling regrowth is a viable approach for selective-area p-type doping in GaN power devices but also open a door for the development of unconventional GaN devices based on p-GaN/2DEG junctions.