The experimental study on negative capacitance(NC) of various light-emitting diodes(LEDs) is presented.Experimental result shows that all LEDs display the NC phenomenon.The voltage modulated electroluminescence(VMEL) ...The experimental study on negative capacitance(NC) of various light-emitting diodes(LEDs) is presented.Experimental result shows that all LEDs display the NC phenomenon.The voltage modulated electroluminescence(VMEL) experiment confirms that the reason of negative capacitance is the strong recombination of the injected carriers in the active region of luminescence.The measures also verify that the dependence of NC on voltage and frequency in different LEDs is similar: NC phenomenon is more obvious with higher voltage or lower frequency.展开更多
In order to explain the phenomenon of negative capacitance(NC) in light emitting diodes LEDs,we present a new model based on local strong recombination in active region and firstly deduce the analytic expression of NC...In order to explain the phenomenon of negative capacitance(NC) in light emitting diodes LEDs,we present a new model based on local strong recombination in active region and firstly deduce the analytic expression of NC from continuity equation.The theoretical result indicates that the NC effect becomes stronger when the carrier recombination rate increases in a certain range,which is consistent with the experimental result.Accordingly,we confirm that the NC is caused by carrier recombination in active region instead of by other exterior factors.展开更多
Frequency responses of modulated electroluminescence(EL)of light-emitting diodes were measured using a testing setup.With increasing frequency of the ac signal,the relative light intensity(RLI)clearly decreases.Furthe...Frequency responses of modulated electroluminescence(EL)of light-emitting diodes were measured using a testing setup.With increasing frequency of the ac signal,the relative light intensity(RLI)clearly decreases.Furthermore,a peculiar asynchrony between the RLI and ac small-signal is observed.At frequencies higher than 10 kHz,the RLI clearly lags behind the ac signal and the absolute value of the lagging angle is nearly proportional to the signal frequency.Using the classical recombination model of light-emitting diodes under ac small-signal modulation,these abnormal characteristics of modulated EL can be clearly explained.展开更多
基金This workis supported by the National Nature Science Founda-tion (Grant No.DMR-60376027)
文摘The experimental study on negative capacitance(NC) of various light-emitting diodes(LEDs) is presented.Experimental result shows that all LEDs display the NC phenomenon.The voltage modulated electroluminescence(VMEL) experiment confirms that the reason of negative capacitance is the strong recombination of the injected carriers in the active region of luminescence.The measures also verify that the dependence of NC on voltage and frequency in different LEDs is similar: NC phenomenon is more obvious with higher voltage or lower frequency.
基金This work was supported by the National Nature Science Foun-dation (Grant No.DMR-60376027) .
文摘In order to explain the phenomenon of negative capacitance(NC) in light emitting diodes LEDs,we present a new model based on local strong recombination in active region and firstly deduce the analytic expression of NC from continuity equation.The theoretical result indicates that the NC effect becomes stronger when the carrier recombination rate increases in a certain range,which is consistent with the experimental result.Accordingly,we confirm that the NC is caused by carrier recombination in active region instead of by other exterior factors.
基金Supported by the National Natural Science Foundation of China under Grant Nos.60876035,50901050,11004148 and 11004149.
文摘Frequency responses of modulated electroluminescence(EL)of light-emitting diodes were measured using a testing setup.With increasing frequency of the ac signal,the relative light intensity(RLI)clearly decreases.Furthermore,a peculiar asynchrony between the RLI and ac small-signal is observed.At frequencies higher than 10 kHz,the RLI clearly lags behind the ac signal and the absolute value of the lagging angle is nearly proportional to the signal frequency.Using the classical recombination model of light-emitting diodes under ac small-signal modulation,these abnormal characteristics of modulated EL can be clearly explained.
