GaN-Based Ultraviolet Light Emitting Diodes With Ex Situ Sputtered AlN Nucleation Layer

Abstract

We demonstrated the electro-optical characteristics of gallium nitride (GaN)-based ultraviolet (UV) light emitting diodes (LEDs) with sputtered aluminum nitride (AlN) nucleation layer. The introduction of the ex situ sputtered AlN nucleation layer improved the crystal quality of the GaN and the n-AlGaN layer of the GaN-based UV LEDs. Hence, the 20-mA output power of UV LEDs with ex situ AlN nucleation layers is higher than that of UV LEDs with GaN nucleation layers. In addition, the enhanced power output of UV LEDs with ex situ AlN nucleation could reach around 52% in magnitude at peak emission wavelengths of 370 nm compared with power outputs of UV LEDs with GaN nucleation layers. Furthermore, UV LEDs with ex situ AlN nucleation show improved reliability. The UV LEDs with ex situ AlN nucleation layer revealed a power output drop of around 9% within 168 hours, which is less than the around 14% power drop of UV LEDs with GaN nucleation layer. Index Terms-GaN-based ultraviolet light-emitting diodes (UV-LEDs), sputtered AlN, nucleation layer.

Improved output power of GaN-based ultraviolet light-emitting diodes with sputtered AlN nucleation layer

“…The nucleation layer between the sapphire substrate and the GaN layer is the key to the dislocation density. Lai et al and Yen et al have employed sputtered AlN nucleation layers in LEDs and achieved improvement of crystal quality [23,24]. In this study, we demonstrate UV-LEDs with a sputtered AlN nucleation layer on PSS.…”

Comparative Research of GaN Growth Mechanisms on Patterned Sapphire Substrates with Sputtered AlON Nucleation Layers

“…At stage 2, the collision of large GaN crystals generated many interfaces, and the GaN film could not coalesce, observed in Figure 2 b. If the thin, low-temperature MOCVD GaN NL was deposited on the PSS, or there was no NL on the cones of the PSS, GaN mostly nucleated on the cones [ 6 , 19 , 22 ].…”

“…Compared to MOCVD-grown AlN or GaN NLs, Li-Chuan Chang et al found that the utilization of ex situ sputtered AlN NLs could suppress GaN nucleation on cones and improve the quality of GaN films on PSSs [ 17 ]. Subsequently, many works proved that the utilization of sputtered AlN/PSS templates could improve the performance of GaN-based LEDs [ 18 , 19 ]. However, small GaN crystals on the cones’ surface of sputtered AlN/PSS templates may still deteriorate the crystal quality [ 15 , 20 , 21 ].…”

Investigation of AlGaN/GaN Heterostructures Grown on Sputtered AlN Templates with Different Nucleation Layers

“…Among them, the sputtered AlN template on a sapphire substrate has attracted significant attention because the sputtering process supports a high throughput, is largely scalable, is inexpensive, and has been shown to give rise to reduced dislocation densities in the GaN grown thereon [11][12][13]. In terms of device performance, sputtered AlN films have been demonstrated to provide notable improvements in terms of increased light output, lower forward turn on voltage, reduced reverse leakage current, and improved reliability for visible and ultraviolet-light-emitting diodes [14,15].…”