Aging of AlGaN quantum well light emitting diode studied by scanning near-field optical spectroscopy

Abstract

Emission from a 285 nm AlGaN quantum well light emitting diode has been studied by scanning near-field optical spectroscopy. The scans revealed micrometer-size domainlike areas emitting with a higher intensity and at a longer wavelength; presumably, because of a lower AlN molar fraction in these regions. Experiments performed on different days have shown that with time, intensity from these spots increases and emission wavelength shifts to the red, indicating a further change in the quantum well alloy composition. This has allowed distinguishing an aging mechanism that involves locally increased current, heating, and atom migration.

Deep traps in GaN-based structures as affecting the performance of GaN devices

“…Catastrophic degradation observed was attributed to the formation of macroscopic defects [380] or to severe current crowding [381]. Gradual degradation reported in Refs.…”

Optical studies of degradation of AlGaN quantum well based deep ultraviolet light emitting diodes

“…Recently, we have explored a device emitting at 285 nm using scanning near field optical microscopy ͑SNOM͒ and revealed a yet another aging mechanism related to domainlike AlGaN compositional inhomogeneities in the QWs. 4 The latter investigation has shown the power of the SNOM technique in monitoring microscopic changes occurring in deep UV LEDs during aging. In the present work, we examine critical issues in aging of AlGaN QW LEDs, in particular, those with the high Al percentage, by exploring and comparing devices with high and low Al content in the QWs.…”

“…1 However, fabrication of devices emitting at wavelengths shorter than 340 nm is still a great challenge because of the complicated growth of AlGaN structures with high Al content. High number of defects that act as nonradiative recombination centers lead to local heating and current crowding, [2][3][4] and contribute to low quantum efficiency and rapid device aging. During the recent years, a large effort has been devoted to developing technology of AlGaN LEDs with a large percentage of Al.…”

High-quality n-type aluminum gallium nitride thin films grown by interrupted deposition and in-situ thermal annealing

“…A number of methods were utilized to grow high Al mole fractional Al x Ga 1 À x N thin films, such as multiple thin SiAlN interlayers [14], AlN/AlGaN superlattice [15], and pulsed atomic layer epitaxy (PALE) [16]. As a critical figure of merit for crystalline quality, the full width at halfmaximum (FWHM) of X-ray diffraction (XRD) Omegarelated measurements of intrinsic AlGaN was reported to be less than 100 arcsec grown by MOCVD technology [14].…”