Electrothermal considerations in display applications of light-emitting diodes

Some of the possibilities and problems of high-density integration and packaging of light-emitting diode displays are explored, using a new electrothermal characterization of light-emitting diodes. After a brief discussion of thermal effects in spontaneous light-emitting diodes, the characterization is derived. It reveals a peak in luminance with increasing electric power due to self heating. Experimental results confirm the accuracy of the characterization for gallium arsenide phosphide monolithic displays. Finally, the characterization is used to evaluate some projected high power-density applications. These particularly involve dense diode arrays and the use of higher levels of integration, together with magnification by projection of an image onto a screen, to reduce the cost per element associated with processed chip area. Self heating is found to cause a strong dependence of the luminance on the number of elements powered in a dense array, and to limit severely the achievable magnification even with improved packaging.