Vertical injection thin-film AlGaN∕AlGaN multiple-quantum-well deep ultraviolet light-emitting diodes

Abstract

Vertically injected thin-film ultraviolet light-emitting diodes operating at 325 and 280nm are demonstrated. Low-temperature AlN interlayers allow crack-free growth of AlxGa1−xN with compositions up to x=0.53 on GaN-on-sapphire templates. The GaN layer allows laser-induced separation of the highly strained epi stack from the sapphire substrate with high yield. Cathode contacts are formed on nitrogen-face AlxGa1−xN (up to x=0.53) and allow vertical injection of current into the active region. Controlled roughening of the nitrogen-face AlxGa1−xN is also demonstrated through photoelectrochemical etching and results in >2.5× light extraction gain for 325 and 280nm devices.

High-power UV-B LEDs with long lifetime

“…Various techniques have been employed to increase the light extraction efficiency by means of back side roughening, pattern formation, dry etching and plasmonics. [17][18][19][20] In our samples, no treatment of the backside of the sapphire substrate was undertaken as the typical RMS roughness of 1.4 µm provided by the manufacturer was found to result in an approximately 30% higher extraction efficiency as compared to a substrate with a polished backside. This observed increase in the extraction efficiency is due to the scattering of photons which results in the extraction of photons that have not been initially emitted into the escape cone.…”

III-Nitride-Based Short-Wavelength Ultraviolet Light Sources

“…Moreover, the slope of the curve improved due to better light extraction after flip-chip packaging. Several groups have also started research efforts aimed at developing DUV LEDs with vertical conduction (Kawasaki et al, 2006;Zhou et al, 2006). For the reported works, the DUV LEDs are grown over sapphire substrates with a GaN buffer layer.…”

Design and comparative study of lateral and vertical LEDs with graphene as current spreading layer

“…Although V-LEDs have small internal resistance, current spreading is still a severe problem in high power applications. The small-area top n-contacts and largebackside reflective p-contacts cause current crowding in V-LEDs [13,[16][17].…”