Realization of Low Dislocation Density AlN on Patterned Sapphire Substrate by Hydride Vapor‐Phase Epitaxy for Deep Ultraviolet Light‐Emitting Diodes

Herein, the characteristics of AlN epilayers grown directly on hole‐type patterned sapphire substrate (HPSS) by hydride vapor‐phase epitaxy (HVPE) are reported. To investigate the effect of HPSS, the threading dislocation densities (TDDs) of AlN films grown simultaneously on HPSS and flat sapphire substrate (FSS) are analyzed by transmission electron microscopy. The corresponding TDD is measured to be 4.38 × 108 cm−2 for the AlN sample grown on HPSS, which is significantly lower than the value of 1.48 × 109 cm−2 on the FSS. The usability of the AlN/HPSS template for deep ultraviolet (DUV) light‐emitting diodes (LEDs) is proven by growth of AlGaN‐based LED structure emitting at 278 nm with single peak emission in a metal‐organic chemical vapor deposition reactor. The light output power of flip‐chip LED grown and fabricated on AlN/HPSS template is enhanced by a factor of 1.25 when compared with LED on AlN/FSS template at 350 mA injecting current. These results suggest that the high‐quality AlN template grown on properly designed HPSS by HVPE can make a significant contribution toward the realization of highly efficient nitride‐based DUV‐LEDs. By introducing the hole‐type patterned sapphire substrate (HPSS) with a properly designed pattern configuration as a substrate for AlN growth, threading dislocation density (TDD) is significantly lowered from 1.48 × 109 to 4.38 × 108 cm−2. The TDs on the mesa zones generated at AlN/sapphire interface can be effectively suppressed by bending toward coalescence zone during the subsequent lateral overgrowth.