Carbon doped semi-insulating freestanding GaN crystals by ethylene

Semi-insulating freestanding GaN crystals are excellent candidates for substrates of GaN-based power electronic devices. Carbon doping is believed to be currently the optimal way to achieve semi-insulating GaN crystals grown by halide vapor phase epitaxy (HVPE). Here, we demonstrate that ethylene is an excellent source for C doping, where the doping efficiency is much higher than that of methane. Under the same carbon mole flux, the carbon incorporation rate of ethylene is 40 times in magnitude higher than that of methane. A record highest resistivity is achieved by ethylene doping with a carbon concentration of 1.5 × 1020 cm−3. Our work demonstrates that ethylene is an excellent carbon dopant source for HVPE-grown GaN crystals.