Potential application of p–i–n semiconductor capacitor with non-linear voltage–charge characteristic for secondary battery

We carried out the time-dependent drift–diffusion simulation to study a capacitor with semiconductor electrodes and its potential application for a battery-like operation. We employed the p– i– n and p– n structures with an insulator inserted in the middle of the devices. Both devices can store and retain the charge and voltage without any degradation, thanks to the insulator which inhibits carrier recombination. Additionally, they have a strong non-linear dependence between the stored charge and voltage, whereas a conventional capacitor shows linearity. The non-linearity is induced as follows. The junction capacitance dominates under smaller bias than the built-in potential. When the voltage exceeds the built-in, the capacitance associated with the insulator characterizes the charge–voltage relation. The intrinsic layer further enhances the non-linearity and keeps the output voltage high until the stored charge becomes significantly small due to its small capacitance. As a result, the p– i– n like structure with the insulator stores larger energy than that of the conventional capacitor and realizes the battery-like operation.