Heteroepitaxial Growth of High-Quality and Crack-Free AlN Film on Sapphire Substrate with Nanometer-Scale-Thick AlN Nucleation Layer for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

Abstract

High-quality and crack-free aluminum nitride (AlN) film on sapphire substrate is the foundation for high-efficiency aluminum gallium nitride (AlGaN)-based deep ultraviolet light-emitting diodes (DUV LEDs). We reported the growth of high-quality and crack-free AlN film on sapphire substrate with a nanometer-scale-thick AlN nucleation layer (NL). Three kinds of nanometer-scale-thick AlN NLs, including in situ low-temperature AlN (LT-AlN) NL, oxygen-undoped ex situ sputtered AlN NL, and oxygen-doped ex situ sputtered AlN NL, were prepared for epitaxial growth of AlN films on sapphire substrates. The influence of nanoscale AlN NL thickness on the optical transmittance, strain state, surface morphology, and threading dislocation (TD) density of the grown AlN film on sapphire substrate were carefully investigated. The average optical transmittance of AlN film on sapphire substrate with oxygen-doped sputtered AlN NL was higher than that of AlN films on sapphire substrates with LT-AlN NL and oxygen-undoped sputtered AlN NL in the 200–270 nm wavelength region. However, the AlN film on sapphire substrate with oxygen-undoped sputtered AlN NL had the lowest TD density among AlN films on sapphire substrates. The AlN film on sapphire substrate with the optimum thickness of sputtered AlN NL showed weak tensile stress, a crack-free surface, and low TD density. Furthermore, a 270-nm AlGaN-based DUV LED was grown on the high-quality and crack-free AlN film. We believe that our results offer a promising and practical route for obtaining high-quality and crack-free AlN film for DUV LED.

The Effect of Nanometer‐Scale V‐Pit Layer on the Carrier Recombination Mechanisms and Efficiency Droop of GaN‐Based Green Light‐Emitting Diodes

“…Pits caused by the TDs or stacking faults as reported in previous studies are observed. [ 31–34 ] The threading dislocation densities of these three experimental samples, MQW1, MQW2, and MQW3, are of the order of 1–2 × 10 8 cm −2 , as shown in Figure . The V‐shaped pits are formed around the TDs.…”

“…The V‐pit layer could reduce the leakage current, enhance the radiative recombination efficiency, and relieve the efficiency droop of GaN‐based LEDs. [ 31–34 ] The research results also show that the use of QD technology can effectively improve the luminous efficiency of GaN‐based green LEDs. [ 27–30 ] In this article, we modified the morphology of residual dislocations by using a compound V‐pit layer.…”

Recent Progress in Micro‐LED‐Based Display Technologies

“…[32,33] Although, sapphire remains the dominant substrate material for the epitaxy of nitrides LEDs, because it allows lower dislocations densities and the best crystalline quality. [34] But the use of large Si substrates also attracts great interest due to its availability in the market at a lower cost. Further, the growth over Si could be useful to integrate nitrides with silicon standard electronics.…”

Physical and technological analysis of the AlGaN-based UVC-LED: an extended discussion focused on cubic phase as an alternative for surface disinfection.

“…Another consideration is required since III-V alloy components have different lattice constants; therefore, an AlN buffer layer must be grown to replicate the substrate structure in order to avoid cracks and reduce dislocations [97]. The following layer on the hexagonal AlN must be designed to improve the LED technology and its efficiency [98].…”