Stress‐Induced Dark Line Defect Formation in GaAlAs : Si LED's

• Published in: Journal of the Electrochemical Society 1981-03, Vol.128 (3), p.661-669
• Main Authors: Chin, A. K., King, W. C., Leonard, T. J., Roedel, R. J., Zipfel, C. L., Keramidas, V. G., Ermanis, F.
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.2127477

Homojunction, graded bandgap GaAlAs:Si LED's have been demonstrated to be highly reliable. It has recently been found that some LED's show a rapid reduction of light output even when aged without current bias at 200 deg C. < 100 > oriented dark lines appeared in the electroluminescence image of heavily degraded devices. To determine the source of the DLD's, the material quality of degraded LED's and unaged LED's from the same wafer was assessed using etch pitting and transmission cathodoluminescence. Examination of the devices revealed the presence of small pyramids, composed mainly of Si, on the p-surface of some of the LED's; no unusual features were found on the remaining LED's. A dislocation network surrounding each pyramid was found to be initially present. Due to bonding and thermal stresses applied to the pyramids, these networks enlarged with aging along the {111J planes and appeared as < 110 > DLD's in the electroluminescence image upon reaching the p -- n junction.23 refs.--AA