| High brightness light emitting diodes could be used in the fields of large outdoor display, traffic signal lights, automotive light and backlighting of liquid crystal display. It also has another potential, for example, it may be used as replacement of incandescent bulbs for lightening in the future. For being with many advantages, it has been an active subject in recent years and much progress has been made. On the basic of analysis of many kinds of LED structures, a new kind of strained layer structure has been introduced into our designed HB-LED which has been manufactured in our laboratory to demonstrate a even higher efficient light emission. Through calculation of LED external quantum efficiency, a method for design HB-LED top layer was evaluated. The main work is as following:1 The history and trend of HB-LED were briefly described. The obstacles in developing HB-LED were analyzed and the main work in this thesis was pointed out.2 The energy structures of GalnP/GaAlInP bulk material, quantum well, multi-quantum wells and strained quantum well were theoretically analyzed and calculated. For the compressively strained layer, the heavy-hole state is moved to higher energy and the light-hole state to lower energy due to the shear-deformation potential.3 The carrier transportation and transition in LED active layer had been analyzed. The larger number of quantum wells are in active layer, the lower carrier density will be, and the better confinement of carrier is. The coefficient transition in quantum well is larger than that in bulk material.4 Design of HB-LED is focused on MQWs and top layer. Compensatory MQWs for LED active layers have led to good results follow the analysis in former two chapters. Systematic analysis of current injection and light output Via external quantum efficiency of HB-LED showed mat the optimum of top layer of HB-LED is appeared to be between 15 u m and 20 u m, and at least is 5 u m.5 GalnP, GaAlInP and GaP material had been grown by turbo-disk LP-MOCVD. The growth parameters have been optimized comprehensively to include the operation of the machine, character of precursors, the techniques especially for GaAlInP material growth and the substrate processing. The epitaxial layer quality of GaAlInP has been specified so well by double-crystal X-ray diffraction that there are many and strong interference in the picture.6 briefly described the procedure of LED fabrication and showed our LED test result. Brightness of more than 2cd for 648nm wavelength LED has been demonstrated at 20mA.
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