Hb-led Device Structure Study

How to enhance the brightness of High Brightness Light Emitting Diode is a valuable problem in theory and in economy. Improving the structure of the chip can greatly enhance the brightness of LED.In this thesis, the effects of applying p-N graded heterojunction instead of p-N abrupt heterojunction have been analyzed theoretically and manufactured experimentally, and great progress has been obtained.In this thesis, each structure in the LED chip has analyzed deeply and systematically. The effect of each structure on the transfer of the carrier, the confinement of the carrier, the recombination of the carrier has been analyzed.The main work is showed as follow:1. Appling p-N graded heterojunction instead of abrupt one is studied deeply in theory, and the conclusion is that it will enhance the current injection ratio, decrease the built- in voltage, improve the quality of the crystal and it will not affect the confinement to the hole. It enhances the brightness effectively.2. The band profile is simulated by the mathematic way. We get the conclusion. When the grading length is comparatively short, the best grading way are Gath and parabolic way. When the grading length is comparatively long, the lineral grading way is the best one. Under the best grading way, the shape of the band profile is more propitious to the transfer of the carrier.3. Under the three different doping densities, we get the least grading length to make the spike vanish. We get the conclusion: The higher the doping density is ,the shorter grading length is wanted to make the spike vanish.4. As there is some difficulty to manufacture the graded heterojunction, we put forward that it can use double layer abrupt heteojunction to take the place of the graded heterojunction. We get the best distributions of the two layer and the best abrupt position. From the result of the practice, this structure enhances the brightness of LED effectively, improves the quality of the crystal and improves the performance of the device.5. A formula is deduced to calculate the built-in voltage of the compound semiconductor. We can get some important parameters from the built-in voltage. The formula is more simply and useful than the orthodox one, and the accuracy is high.6. The effect of the DH on the HB-LED is analyzed. Applying DH can enhance the injection ratio, strengthen the confinement to the carrier and enhanced the efficiency of the recombination. This make the brightness greatly enhance. The mathematic model of DH is educed. The growth of DH is summarized.7. The effect of the MQW on the HB-LED is analyzed. Al content will decrease if using MQW even the same emitting wavelength. And it will improve the quality of the crystal. MQW have the same effect on HB-LED as DH, but better than that. The mathematic model is educed. The growth of MQW is summarized.