J. Rass^1,2, J. Ruschel¹, J. Glaab¹, I. Ostermay¹, and S. Einfeldt¹

Published in:

IEEE Photonics Technol. Lett., vol. 32, no. 16, pp. 1007-1010 (2020).

Abstract:

AlInGaN-based light emitting diodes (LEDs) emitting in the ultraviolet (UV) wavelength range around 310 nm were fabricated using 300 nm thick SiN_x or SiO₂ layers deposited by different types of plasma enhanced chemical vapor deposition (PECVD) for electrical insulation. The composition, deposition technique, and thermal treatment of the insulator were varied and its influence on the breakdown voltage, step coverage, and degradation behavior of the UVB LEDs was studied. LEDs with SiN_x layers deposited by PECVD in a capacitively coupled (CC) deposition process at high temperatures showed the highest conformity, highest breakdown voltages, but also the fastest degradation. The degradation was reduced by annealing the wafers after the insulator deposition. If the SiN_x or SiO₂ was deposited by inductively coupled IC-PECVD instead, the conformity and breakdown voltages decreased. Insulators deposited by IC-PECVD showed a high rate of sudden failures during the first 1,000 h of operation. Studies of the hydrogen content in the SiN_x layer showed that the insulator with the highest hydrogen content (SiN_x by CC-PECVD) resulted in the fastest degradation, while that with the lowest hydrogen content (SiO₂ by IC-PECVD) showed a slower degradation.

Index Terms:

Dielectric breakdown, insulators, ultraviolet (UV) sources, light emitting diodes (LEDs), aluminium gallium nitride, silicon nitride, dielectric films, epitaxial layers, wide bandgap semiconductors, aging, degradation, materials reliability, semiconductor device reliability.

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