Structural and optical characterizations of GaN-based green light-emitting diodes growth using TiN buffer layer

Abstract

The present study investigated the structural and optical characterizations of the growth of GaN-based green light-emitting diodes using a TiN buffer layer. The purpose of growing GaN-based green LEDs on the TiN interlayer was to produce the naturally occurring hexagonal pattern structure on the surface of undoped-GaN. Then dislocations of the grown InGaN/GaN MQWs green LEDs structure on the uGaN template with the TiN interlayer produced base plane staking faults through epitaxial lateral overgrowth. Cross-section transmission electron microscope images showed that the dislocation density of green LEDs was decreased from 5 x 10(8) cm(-2) to 7 x 10(7) cm(-2), and that the dislocations in the green LEDs structure were reproduced. The full widths at half maximum of the omega-scan rocking curves in (002) and (102) reflectance on the GaN-based green LEDs were 334 and 488 arcsec, respectively. As the injection current was increased from 5 mA to 40 mA, the electroluminescence peak wavelength of the GaN-based green LEDs was shifted from 508 nm to 481 nm, a blue-shift of 27 nm. The forward voltage measured at an injection current of 20 mA was 4.9 V for the GaN-based green LEDs according to the current-voltage characteristics. Due to an increase in the In mole fraction of the GaN-based green LEDs on the uGaN template with the TiN interlayer, the strain and phase separation were increased, and the multiple quantum wells structural quality and device performances of the GaN-based green LEDs were decayed. A yellow band with a wavelength of 551nm was thereby produced according to room temperature photoluminescence measurement. Meanwhile, cross-section transmission electron microscope images indicated V-defects in multiple quantum wells structures of the green LEDs.