Current-induced degradation of high performance deep ultraviolet light emitting diodes

Abstract

Lifetime measurements on single-chip, packaged 285 nm light-emitting diodes (LEDs) performed under constant current injection at 20 and 75 mA, were compared to the performance of unbiased LEDs baked at the equivalent operating junction temperatures. The thermally stressed devices showed a lesser degradation than those electrically stressed, indicating that elevated temperature alone does not cause degradation. Despite a decay to less than half of the initial power under current injection, time-resolved photoluminescence of the active region exhibits little change, while capacitance-voltage measurements imply that the reduced efficiency and power decay originate from the generation of point defects near the p-side of the p-n junction.

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

“…Gradual degradation reported in Refs. [382][383][384] was not related to increased nonradiative recombination in the MQW region, but rather ascribed to generation of defects in the AlGaN cladding layers. The effect was variously explained by migration of Al in the p-AlGaN cladding layer or to enhanced compensation of p-type conductivity in this layer.…”

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

“…So far, aging of LEDs with emission wavelength as short as 280 nm has been studied by measuring electrical, far field optical, and noise properties. 2,3,[5][6][7] Aging mechanisms, such current crowding around contacts, 2 at macroscopic defects, 3 generation of defects 5 and change in alloy composition in the p-side cladding layer 7 have been proposed. 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.…”

Characterization of failure modes in deep UV and deep green LEDs utilizing advanced semiconductor localization techniques.

“…Recent studies of UV LED degradation have identified a discrepancy between PL and EL measurements. 5,9,10 The degradation in PL (which targets the quantum wells) is either negligible or significantly less than the orders of magnitude decrease in photon counts encountered in the EL measurements. This suggests that the degradation is not occurring in the active region but more likely in the p-type cladding material increasing the number of nitrogen vacancies.…”

“…Multiple degradation mechanisms have been proposed, including device self-heating, 1 an increase in non-radiative recombination, 2 compositional inhomogeneities, 3 Al atom migration from the p-cladding layer, 4 compensation of p-type doping or generation of point defects in the cladding layer, 5,6 and current crowding around contacts 7 as well as at macroscopic defects. 8 The degradation mechanism(s) occurring in the III-nitride devices are complex and may involve point-defects, making exact identification of those mechanisms quite difficult.…”

“…This suggests that the degradation is not occurring in the active region but more likely in the p-type cladding material increasing the number of nitrogen vacancies. 5,9,10 As defect signals are localized and observed by TIVA/LIVA in this work, these defect types and degradation mechanisms will be considered.…”