GaN-Based LEDs Grown on HVPE Growth High Crystalline Quality Thick GaN Template

Abstract

In this study, high crystalline quality 30 μm thick gallium nitride (GaN) films were grown by hydride vapor phase epitaxy (HVPE) on sapphire substrate, and the thick GaN films were used for developing high performance light-emitting diodes (LEDs). By using high-resolution X-ray diffraction, the full width at half-maximum (FWHM) of the rocking curve shows that this 30 μm thick GaN template had high crystalline quality. In addition, the transmission electron microscopy (TEM) images suggest that threading dislocation densities (TDDs) are almost free in multiple quantum wells (MQWs) for LEDs grown on 30 μm thick GaN template. Compared with conventional LEDs grown on sapphire, LEDs grown on 30 μm thick GaN template exhibit 26% enhancement of light output at 20 mA.

Enabling High-Injection Current Light-Emitting Diodes Prepared on 10-$\mu \text{m}$ -Thick GaN Films Grown by Hydride Vapor Phase Epitaxy

“…Compared with LED-R, LED-1, and LED-2 had 47.8% and 20.1% higher output power, respectively. Such great enhancement in light output power results from the improved crystal quality and released strain of the films [11]. Therefore, the EL emission peak wavelength, Raman spectrum, and relative internal quantum efficiency (IQE) were measured to support the conclusion mentioned above.…”

“…The Raman spectra of the samples grown through step-1 and step-2 uGaN growth were measured. The Raman shifts of the (Table I), while the unstrained GaN epitaxial layer was located at 566.5 cm −1 [11]. The Raman shift of the E 2 high mode for sample-1 and sample-2 shifted to a low frequency because of the thick GaN films grown through HVPE.…”

“…As the injection current was increased from 2 to 100 mA, the emission peak wavelength of the LEDs exhibited blueshift of 4.8, 3.1, and 3.9 nm for LED-R, LED-1, and LED-2, respectively. This result indicates that LED-R had serious QCSE than the LEDs grown on the 10-μm-thick uGaN template possibly because of the residual strain of the GaN layer [11]. To discuss the residual strain of the GaN films, μ-Raman spectra were obtained at room temperature.…”

“…However, the HVPE still suffers from a complicated procedure in terms of preparing the templates. In conventional HVPE growth, a 3-μm-thick undoped GaN (uGaN) film must first be prepared through the MOCVD [11]. In this paper, we integrated the advantages of the ex situ-sputtered AlN nucleation layer and PSS to realize the uninterrupted GaN epitaxy of high-crystal-quality thick GaN films in HVPE.…”

Enhanced Light Output Power and Growth Mechanism of GaN-Based Light-Emitting Diodes Grown on Cone-Shaped ${\hbox{SiO}}_{2}$ Patterned Template

“…It has been reported that the improvement of the crystalline quality can effectively enhance the internal quantum efficiency (IQE) of the InGaN/GaN multiple quantum wells (MQWs) [32]. In order to clarify the correlation between the crystalline quality and IQE for LED grown on planar sapphire substrate, CPSS and cone-shaped SiO patterned template, the photoluminescence (PL) internal quantum efficiency (IQE) measurement was performed.…”