Deep defects in InGaN LEDs: modeling the impact on the electrical characteristics

Roccato, Nicola; Piva, Francesco; Santi, Carlo De; Brescancin, Riccardo; Mukherjee, Kalparupa; Buffolo, Matteo; Haller, Camille; Carlin, J.-F.; Grandjean, N.; Vallone, Marco; Tibaldi, Alberto; Bertazzi, Francesco; Goano, Michele; Verzellesi, Giovanni; Meneghesso, Gaudenzio; Zanoni, Enrico; Meneghini, Matteo

doi:10.1117/12.2606560

Cited by 1 publication

(1 citation statement)

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“…We ascribed the increase in drive voltage to the degradation of the pcontact due to a passivation of Mg dopant in the first nanometers of p-GaN, caused by the current flow [8]. The increase in TAT components was correlated to an increase in defectiveness in the active region, as suggested by Roccato et al in [12] for InGaN-based LEDs. Finally, the increase in shunt current components was ascribed to the increase in current leakage paths, possibly located at the mesa edge of the device [13]- [15].…”

Section: Resultsmentioning

confidence: 61%

Degradation of AlGaN-based SQW UV-C LEDs investigated by capacitance deep level transient spectroscopy

Piva

Buffolo²,

Santi³

et al. 2023

Gallium Nitride Materials and Devices XVIII

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The market of Ultraviolet (UV) Light Emitting Diodes (LEDs) is expected to expand substantially in the coming years, thanks to the disinfection properties of the UV light; however, a detailed study on the reliability-limiting processes is a fundamental step, for an effective deployment of this technology. We investigated the degradation mechanisms of AlGaN-based UV Single Quantum Well (SQW) LEDs, with a nominal emission wavelength of 265 nm, an area of 0.1 mm2 and a nominal current density of 100 A·cm-2. By means of constant current stress test and Capacitance Deep Level Transient Spectroscopy (C-DLTS) we studied the main electrical, optical, spectral and capacitance characteristics of the devices, in order to understand the dominant causes of degradation. For aged devices the electrical characterization shows increased subthreshold leakage currents, due to the increase in Trap Assisted Tunneling (TAT) components, as well as an increase in drive voltage, which is ascribed to contact degradation or a decrease in injection efficiency. The optical output power showed a decrease especially at low current levels, which has been ascribed to an increase in non-radiative recombination and suggests the generation of defects in the LED active region. C-DLTS measurements showed in unaged devices the presence of two defects in the structure, both ascribed to magnesium (Mg), located at 475 meV and 150 meV from the respective band. Moreover, we detected the increase in concentration of a third defect during the stress test with an activation energy of 700 meV, that acts as a point defect, and could be ascribed to gallium vacancies or nitrogen antisites.

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