The Effect of Dislocations in Ga1 − x Al x As : Si Light‐Emitting Diodes

Solid-state lighting is a rapidly evolving, emerging technology whose efficiency of conversion of electricity to visible white light is likely to approach 50% within the next several years. This efficiency is significantly higher than that of traditional lighting technologies, giving solid-state lighting the potential to enable significant reduction in the rate of world energy consumption. Further, there is no fundamental physical reason why efficiencies well beyond 50% could not be achieved, which could enable even more significant reduction in world energy usage. In this article, we discuss in some detail: (a) the several approaches to inorganic solid-state lighting that could conceivably achieve "ultra-high," 70% or greater, efficiency, and (b) the significant research questions and challenges that would need to be addressed if one or more of these approaches were to be realized.

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“…Early work on near-infrared LEDs in previously studied materials, particularly GaAs [27] and AlGaAs [76]…”

Section: Extended Defectsmentioning

confidence: 99%

Research challenges to ultra‐efficient inorganic solid‐state lighting

Phillips¹,

Coltrin

Crawford

et al. 2007

Laser & Photonics Reviews

375

268

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“…Threading dislocation ͑TD͒ densities greater than ϳ10 4 cm −2 significantly decrease the efficiencies of GaP and GaAs based optoelectronic devices. [1][2][3] Fortunately, GaN optoelectronic devices perform reasonably well even with much higher TD densities ͑as high as 10 10 cm −2 ͒. 4 GaN-based devices, however, can be deleteriously impacted by TDs and a significant body of research has focused on decreasing the TD densities in these films to improve device performance.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of threading dislocation densities in In- and N-face InN

Gallinat

Koblmüller

et al. 2010

Journal of Applied Physics

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The threading dislocation ͑TD͒ structure and density has been studied in In-and N-face InN films grown on GaN by plasma-assisted molecular beam epitaxy. The TD densities were determined by nondestructive x-ray diffraction rocking curve measurements in on-axis symmetric and off-axis skew symmetric geometries and calibrated by transmission electron microscopy measurements. TD densities were dominated by edge-type TDs with screw-component TDs accounting for less than 10% of the total TD density. A significant decrease in edge-type TD density was observed for In-face InN films grown at increasingly higher substrate temperatures. In-face InN films grown with excess In exhibited lower TD densities compared to films grown under N-rich conditions. The edge-type TD density of N-face InN films was independent of substrate temperature due to the higher allowable growth temperatures for N-face InN compared to In-face InN. TD densities in In-face InN also showed a strong dependence on film thickness. Films grown at a thickness of less than 1 m had higher TD densities compared with films grown thicker than 1 m. The lowest measured TD density for an In-face InN film was ϳ1.5ϫ 10 10 / cm 2 for 1 m thick films.

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“…On peut par exemple montrer que les dislocations sont des centres de recombinaison non radiatifs qui dégradent fortement l'efficacité optique du matériau. Ce point est illustré en figure 7 sur un ensemble de diodes GaAlAs:Si élaborées par épitaxie en phase liquide [15]. Nous ne traiterons dans ce paragraphe que des défauts de structure, les problèmes liés à l'homogénéité chimique dans les matériaux multi-constitués faisant l'objet de la section 4.…”

Section: Défauts Cristallinsunclassified

“…7. Variation de l'efficacité radiative de 45 diodes GaAlAs:Si en fonction de la densité de dislocations dans la couche épitaxiée [15].…”

Section: Défauts Cristallinsunclassified