Role of light emission and sub‐bandgap defects in the dielectric response of electroluminescent diodes

Abstract

Connection between junction impedance and modulated electroluminescence characteristics of light emitting devices of III‐V compounds is probed at low frequencies (≤100 kHz). Negative capacitance effect is observed accompanied by the onset of qualitatively similar modulated light emission as a systematic function of modulation frequency. Interdependent optical and electrical response at such low frequencies is explained by the role of defects in charge recombination dynamics which can cause reduction of radiative recombination efficiency for high frequency applications. Time domain behaviour of the negative capacitance has also been studied. Occurrence of negative capacitance can be identified by the monotonically decreasing shape of the current transient derivative. The characterization techniques used here can be helpful in optimizing the design of devices based on nitrides of III‐V compounds. However a more rigorous theoretical frame work is required for further analysis which may not follow the conventional semiconductor diode models based on depletion approximation and electrostatic description.