| GaN-based devices have been extensively utilized in LED, laser diodes and power transistors because of the unique optoelectronic properties. However, the lack of GaN bulk substrate leads to an inevitable dislocation issue due to the large lattice mismatch between GaN and common substrates. Dislocations play the roles of non-radiative recombination centers, charged scattering centers, and leakage current pathways to degrade the performance of GaN-based devices. Therefore, many growth methods have been developed to reduce threading dislocation (TD) density in GaN.;GaN growth on patterned sapphire substrate with serpentine channels is proposed for shorter growth time, larger dislocation-free region and lower fabrication cost, compared to conventional epitaxial lateral overgrowth (ELO) methods. The fact that TDs can not switch the propagation direction twice (between vertical and lateral) with constant growth conditions is the mechanism of dislocation reduction by the serpentine channels.;Selective nucleation and growth were successfully conducted on the patterned substrate using well-control depletion region of TMGa. TDs originated from GaN/sapphire interface were fully blocked away from device-active region. In c-GaN case, excellent CL intensity at 365 nm wavelength and low etched-pit density (4x105 cm-2) represented the high crystalline quality of c-GaN. However, because of unintentional enhancement of local growth rate and rough dielectric mask surface, the degradation of crystal quality occured in a-GaN, which was investigated by TEM, CL examinations with the etched-pit density of 1.9x108 cm -2. |
