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. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dynamics of electronic transitions and frequency dependence of negative capacitance in semiconductor diodes under high forward bias

“…This variation of lnf Max with applied bias is plotted in Figure 3(b). Such linear variation of ln f Max with V dc validates our conceived equation (2). Values of the slopes are found to be À4.3 6 0.1 for lower frequency and À13.0 6 0.3 for higher frequency response.…”

“…Dynamics of electronic transitions and frequency dependence of negative capacitance in semiconductor diodes under high forward bias Kanika Bansal,1 Mohamed Henini, 2 Marzook S. Alshammari, 3 and Shouvik Datta We observed qualitatively dissimilar frequency dependence of negative capacitance under high charge injection in two sets of functionally different junction diodes: III-V based light emitting and Si-based non-light emitting diodes. Using an advanced approach based on bias activated differential capacitance, we developed a generalized understanding of negative capacitance phenomenon which can be extended to any diode based device structure.…”

“…Subsequently, a transient change in the charge carrier population coming from these defects can surface, giving rise to a compensatory current and hence the negative capacitance. 1,2 In this region II of Figure 2(b), the contribution from relatively faster defect channels reduces with decreasing frequency. This requires further increase in the applied bias to generate significant contribution from shallower and faster channels which compete with slower channels to produce NC.…”

“…This increases n Trapped and hence the magnitude of compensatory current which ultimately increases the magnitude of NC at decreasing modulation frequencies, as observed in the past. 1,2 However, in case of non-luminescent Si-based diodes, such fast ($ps) radiative recombinations do not take place. Yet the occurrence of NC points towards the presence of mutually competing different rate-limited electronic processes with different time scales.…”

Negative activation energy and dielectric signatures of excitons and excitonic Mott transitions in quantum confined laser structures

“…Earlier, we explored [30][31][32] the connection between voltage modulated electroluminescence (VMEL) and electrical properties of GaInP/AlGaInP based MQW lasers. Under low frequency modulation, we demonstrated the mutual nonexclusivity of radiative and non-radiative transitions.…”