Evidence of Negative Capacitance and Capacitance Modulation by Light and Mechanical Stimuli in Pt/ZnO/Pt Schottky Junctions

Abstract

We report on the evidence of negative capacitance values in a system consisting of metal-semiconductor-metal (MSM) structures, with Schottky junctions made of zinc oxide thin films deposited by Atomic Layer Deposition (ALD) on top of platinum interdigitated electrodes (IDE). The MSM structures were studied over a wide frequency range, between 20 Hz and 1 MHz. Light and mechanical strain applied to the device modulate positive or negative capacitance and conductance characteristics by tuning the flow of electrons involved in the conduction mechanisms. A complete study was carried out by measuring the capacitance and conductance characteristics under the influence of both dark and light conditions, over an extended range of applied bias voltage and frequency. An impact-loss process linked to the injection of hot electrons at the interface trap states of the metal-semiconductor junction is proposed to be at the origin of the apparition of the negative capacitance values. These negative values are preceded by a local increase of the capacitance associated with the accumulation of trapped electrons at the interface trap states. Thus, we propose a simple device where the capacitance values can be modulated over a wide frequency range via the action of light and strain, while using cleanroom-compatible materials for fabrication. These results open up new perspectives and applications for the miniaturization of highly sensitive and low power consumption environmental sensors, as well as for broadband impedance matching in radio frequency applications.

Bipolar Resistive Switching in Lanthanum Titanium Oxide and an Increased On/Off Ratio Using an Oxygen-Deficient ZnO Interlayer

“…W/LTO/TiN devices with ZnO or ZnOF interlayers (Figure S12b–e) exhibit negative capacitance compared with W/LTO/TiN without an interlayer (Figure S12a), which can be attributed to negative capacitance in ZnO (Figure S13). Negative capacitance has been observed in ZnO-related structures previously and can be linked to interface charge density variations, causing less electron capture than electron loss due to hot electron injection. − Previous studies have considered the oxygen ion migration process, including migration paths and migration energy barriers, for perovskite and other metal oxides. Density functional theory (DFT) studies suggest an oxygen ion migration barrier associated with the migration path space, and hence increased migration space (e.g., vacancy sites) can promote oxygen ion migration to neighboring sites .…”

Ensemble GaAsSb/GaAs axial configured nanowire-based separate absorption, charge, and multiplication avalanche near-infrared photodetectors

“…The negative capacitance observed at lower frequencies very likely originates from the accumulation of charge carriers at the interface and/or charging/discharging of the traps arising from the impact loss process, where excess energy gained by electrons in the high E -field knock-off electrons trapped in the states below the Fermi level. 41 Also, it is to be pointed out that at lower frequencies, the impedance associated with the capacitance becomes so large that the values are not representative of the true capacitance value. However, the trend in the onset of the negative capacitance occurring at a lower bias region with lower frequency is indicative of the probing of larger trap cross section.…”

Negative Capacitance Behavior at Low Frequencies of Nitrogen-Doped Polyethylenimine-Functionalized Graphene Quantum Dots-Based Structure

“…Therefore, N ss has an important role in the impedance measurements and NC behavior and an anomalous peak in the C−V and G/ω−V plots, especially at low frequencies in MS and MIS-type structures. 48 When looking at high frequencies, no significant increase in capacitance values was observed because the charges at the interface cannot follow the AC signal and so can not contribute to the real values of C and G/ω. This is because they have a lifetime (τ) higher than 1/ω (ω = 2πf = 2π/T is angular frequency).…”

“…stated that an increase in electron trap density in bipolar organic diodes increased in NC. Joly et al observed NC values over a broad frequency range (20 Hz to 1 MHz). Al-Dharob et al measured temperature-dependent ( C / G /ω /– V ) properties of a metal–polymer–semiconductor structure and observed NC behavior.…”

“…The NC behavior on the C−V profile was attributed to the presence of N ss , R s , and minority carrier injection by Tanrıkulu et al, 46 and Niu et al 47 stated that an increase in electron trap density in bipolar organic diodes increased in NC. Joly et al 48 observed NC values over a broad frequency range (20 Hz to 1 MHz). Al-Dharob et al 49 measured temperature-dependent (C/G/ω /− V) properties of a metal−polymer−semiconductor structure and observed NC behavior.…”