发光二极管放电实验现象分析

利用直流电源对发光二极管(LED)的结电容充电,切断直流电源后对LED的电压-时间特性进行测量。当充电电压低于LED复合发光的门槛电压,LED的电压-时间特性与普通二极管的相似。当充电电压高于LED复合发光的门槛电压,首次观察到:开始放电的瞬间会出现一个快速下降过程,快速下降到门槛电压以下;LED上的电压越高,快速下降到的电压越低。对该现象进行分析,得到一些新的结论。当LED的正偏电压高于复合发光的门槛电压后,出现了注入到扩散区的非平衡载流子随正偏电压的提高而减小的现象,即dQ/du<0。

Analysis of the Discharge Phenomena of Light-emitting Diodes

The forward current-voltage characteristic and forward capacitance-voltage characteristic measurements are the most important methods to study the forward electrical characteristic of light-emitting diodes. These methods can be used to characterize the properties of light-emitting diodes. To further understand p-n junction characteristics of light-emitting diodes, a novel method for measuring p-n junction was proposed. A direct current electrical source was used to charge the junction capacitance of light-emitting diodes, and the voltage-time characteristics of light-emitting diode was measured when the direct current electrical source was switched off. If the changed voltage is lower than the threshold voltage of light-emitting diodes, the voltagetime characteristics of light-emitting diodes is like the the carrier recombination and emitting light threshold voltage drop down process on the moment of discharge general diodes. If the charged voltage of is higher than voltage of light-emitting diode, firstly, there is a fast . The end voltage of drop down process is lower than the threshold voltage of light-emitting diodes. If the charged voltage of light-emitting diode is higher, then the end voltage of drop down process is lower. Some new conclusions can be obtained by analysing the discharge phenomena of light-emitting diodes. In fact, the non-equilibrium carriers which infused into the diffusion layer will be recombined and result in the formation of current when the direct changed voltage was switched off. The voltage-time characteristics of light-emitting diodes that we measured and observed reflect the recombination and attenuation process of the non-equilibrium carriers. By the theoretical analysis, we conclude that the non-equilibrium carriers will be less when the direct charged voltage is higher than the threshold voltage. The reason of this phenomenon needs further research.