Research on the Performance Improvement of GaN-Based Ultraviolet Light-Emitting Diode Chips with Magnetron-Sputtered AlN Nucleation Layers

Abstract

In this paper, the influence of magnetron-sputtered AlN nucleation layers with different thicknesses on ultraviolet (UV) light-emitting diode (LED) chips is studied. First, magnetron-sputtered AlN layers with thicknesses of 8, 25, and 42 nm were prepared on a patterned sapphire substrate (PSS). Subsequently, a 2.8 μm-thick GaN layer was epitaxially grown. We found that when the magnetron-sputtered AlN was 25 nm thick, GaN had the best crystal quality and morphology. Therefore, we grew an 800 nm GaN layer on PSS to analyze the initial growth mechanism of the material. The scanning electron microscopy (SEM) images showed that when the thickness of the sputtered AlN layer was 25 nm, the GaN grains on the sidewall of the PSS cone were the least abundant. In addition, according to the selected area electron diffraction (SAED) test, the (011) crystal plane of GaN appeared on the sidewall of the PSS cone. The (011) crystal plane is the semipolar plane of GaN, which is not conducive to the growth of polar GaN materials. Finally, on this basis, we fabricated UV-LED chips. Among them, the UV-LED chips with the 25 nm magnetron-sputtered AlN layer exhibited the best electrical and optical performance. Overall, this work provides a pathway to improve the performance of UV-LED chips.