External-heater-induced negative capacitance in electronic devices

Abstract

Negative capacitance (NC) is considered an extraordinary phenomenon although it is observed in various electronic devices. Based on device-specific properties, numerous mechanisms have been proposed for decades to explain how ordinary positive capacitance values reach negative values at low frequencies under a high voltage bias. In a previous study, we demonstrated that ubiquitous self-heating of devices is a source of NC in organic light-emitting diodes (OLEDs) and hole-only devices. The principal mechanism of the NC is the nonlinear coupling of the real and imaginary parts of admittance, caused by AC temperature modulation. In this study, a simple test applicable to various devices was conducted to monitor the effects of heating on capacitance. External heating by nichrome wires, rather than self-heating, induced NC, which reflected the heat transfer characteristics of the devices considered: an OLED and a Schottky barrier diode. The heating effect was shown to be a basic and common mechanism of NC, independent of device-specific electronic properties. Therefore, self-heating effects must be considered prior to exploring device-specific NC sources in electronic devices.