The degradation of semiconductor light-emitting diodes, high-radiance lamps and lasers

Abstract

Detailed experimental results and suggested theories on the degradation of light-emitting diodes (LEDS), high-radiance lamps and semiconductor lasers are reviewed. Experimental results on LEDS show that a number of light-degrading mechanisms can operate which probably include migration of impurities or point defects. Dislocations when present in high densities also give rise to degradation in LEDS. Extrapolated lives to half intensity of between lo5 and lo7 h have been commonly projected for these devices, and this rather slow rate of degradation appears to have been achieved by minimizing impurity contamination, reducing strain and minimizing the dislocation density in the carrier recombination region.Relatively long lives have also been predicted for high-radiance, high-currentdensity lamps from thermally accelerated life-tests. Dark-spot and dark-line defects have been observed in these lamps, and samples which develop this structure have to be rejected at early stages of testing in order that long lives can be guaranteed. In one case, the dark structure has been shown to result from the formation of tangles of dislocations generated during fabrication. High-current-density lamps which are free from dark structure also have projected lives of between 105 and 107 h.Generally, laser diodes can now be made which have lives in excess of lO4h. As with high radiance lamps, however, if dislocations are present in the active region, then the useful life of the device is reduced to hundreds of hours or less. Considerable care must therefore be exercised in the fabrication and in layer growth procedures to prevent the introduction of dislocations in the active region. Details of the dark structure resulting from dislocations is reviewed and consideration is given to the remaining causes of degradation in lasers.

Dynamic Modeling of Stress-Induced Defect Expansion in VCSELs

“…Reliability studies of VCSELs have found that defects are mainly confined inside the active region, which may likely be due to the built-in strain in the quantum well and/or barrier and the heat generated by the high carrier density as they collide with the lattice and recombine non-radiatively [28], [29]. Our experimental observations also support this finding.…”

Degradation mechanism beyond device self-heating in high power light-emitting diodes

“…[4][5][6] The degradation of light emitting diodes is a multi-faceted problem that involves change of defect population, catastrophic optical destruction, metal diffusion and electrode delamination. 7 It is an elusive subject for research due to the presence of difficulties in identifying a specific degradation mechanism in different types of LEDs. In fact, different causes may dominate even in a single type of diode, and different degradation mechanisms can be observed simultaneously.…”

Rôle des centres profonds dans la dégradation lente des dispositifs électroluminescents

“…Fig. 1. -Evolution typique de la durée de vie moyenne des lasers dans la période de 1970-1978. [Trend in the useful life of lasers over the period [1970][1971][1972][1973][1974][1975][1976][1977][1978] [22]. ]…”

“…The scales along the ordinate can vary over hours to tens of thousands of hours [22].] Cet effet s'observe également sur les caractéristiques, puissance lumineuse émise en fonction du courant direct appliqué, relevées à des stades différents de la dégradation.…”