High Internal Quantum Efficiency of Nonpolar a-Plane AlGaN-Based Multiple Quantum Wells Grown on r-Plane Sapphire Substrate

Abstract

An internal quantum efficiency (IQE) as high as 39% was achieved with the nonpolar a-plane AlGaN-based multiple quantum wells (MQWs) grown on the r-plane sapphire substrate with metal organic chemical vapor deposition technology. Evident fourth order X-ray diffraction satellite peak and intense MQW-related exciton emission peak at a wavelength of 279.2 nm were observed, implying the successful growth of high quality nonpolar aplane AlGaN-based MQWs. It was found that the employment of the trimethyl-aluminum (TMAl) flow duty-ratio modulation method played a crucial role in the epitaxial growth of the nonpolar a-plane AlGaN MQWs with sharp heterointerfaces and high IQE. Moreover, the unambiguous absence of the blue-shift in the MQWs-related exciton emission peak was verified in spite of the increase in the excitation power during the measurement of the excitation power-modulated photoluminescence spectra, indicating a complete elimination of the quantum confined Stark effect in the nonpolar AlGaN-based MQWs.

Graphene-driving strain engineering to enable strain-free epitaxy of AlN film for deep ultraviolet light-emitting diode

“…Therefore, achieving a high-quality epitaxy of AlN films is of particular importance to ensure the excellent performance of DUV photoelectric devices 11 – 13 . Currently, due to the lack of large-size and low-price homogenous substrates, the optimal choice to grow AlN films is usually to perform heteroepitaxial growth on sapphire 14 – 17 . Unfortunately, due to the inherent lattice and thermal expansion coefficient (TEC) mismatches between AlN and sapphire substrate 18 , 19 , even the well-known two-step epitaxy method or epitaxial lateral overgrowth (ELO) technology still inevitably introduces a variety of crystal defects into AlN epilayer 20 – 22 .…”

Improved Optical Properties of Nonpolar AlGaN-Based Multiple Quantum Wells Emitting at 280 nm

“…Moreover, the AlN and AlGaN buffer layers were grown with a two-way pulsed-flows growth technology [14]. The 5-period of nonpolar AlGaN MQWs were grown with the identical growth method and parameters as our previously reported and the thickness of quantum barriers and quantum wells were confirmed to be 10.5 and 3.9 nm both by the X-ray diffraction (XRD) fitting results and transmission electron microscope (TEM) measurements [16]. Two samples were grown with the identical growth parameters except for the duration of dual nitridation process.…”

“…TDPL spectra measured with the temperature varied from 15.5 to 300 K for sample MA (a) and from 13.8 to 300 K for sample MB (b); TRPL decay curves of MQWs and BSFs emission for samples MA and MB measured at 13 K (c).Fig. 4(b)reproduced from Ref [16],. with permission of ACS Publications.…”

Micropyramid Vertical Ultraviolet GaN/AlGaN Multiple Quantum Wells LEDs on Si(111)

“…e nonpolar plane reduces quantumconfined Stark effect (QCSE) from the spontaneous and piezoelectric polarization [12,13]. Zhao et al achieved IQE as high as 39% at 279 nm in a-plane AlGaN-based multiple quantum wells (MQWs) [14]. With the rapid development of crystal growth and the improvement of semiconductor manufacturing processes, micropyramid GaN-based UV LEDs on Si (111) can improve the EQE by SAG, which is ascribed to (1) high GaN crystal quality of lateral-growth [15], (2) semipolar plane of pyramid structure [12], and (3) larger emitting area of six planes of the pyramid.…”