Growing GaN LEDs on amorphous SiC buffer with variable C/Si compositions

The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-Si_xC_1-x) buffer is demonstrated. The a-Si_xC_1-x buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO₂/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different Si_xC_1-x buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of Si_xC_1-x buffer. The C-rich Si_xC_1-x favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the Si_xC_1-x buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Si-rich Si_xC_1-x buffer, the device deposited on C-rich Si_xC_1-x buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively.