Key Takeaways & Executive Findings
- •• Oxide-based programmable diodes with TiN/HfO2/Si/Al structure exhibit stable diode-like I-V characteristics in low-resistance state. • Conduction and rectification are controlled by the interface between the oxygen vacancy filament and the semiconductor electrode. • First-principle simulations reveal the local density of states and band bending, explaining the transport mechanisms. • Electron transport is dominated by Poole-Frenkel emission under forward bias and reverse Schottky-diode behavior under negative bias.
Abstract
In this work, the oxide-based programmable diodes (PDs) with structure of TiN/HfO2/Si/Al are fabricated, and its electron transport mechanisms are investigated. Electrical measurements results depicted that the conduction and rectification performance of oxide-based PDs are mainly controlled by the interface between oxygen vacancies (VOs) consisted filament and semiconductor electrode. The local density of state in filament and band-bending of the PDs are calculated by first-principal simulation. The electron transport in oxide PDs is dominated by Poole−Frenkel emission under forward bias, while under negative bias, the PDs behave like a reverse Schottky-diode. These mechanisms research is necessary for device optimization and circuit design of oxide-based PDs.
1. Introduction
The sudden transition from insulating state to conducting state in metal-oxide material under voltage bias, which was called resistive switching, has attracted significant attention due to its application in electron devices, especially in memories. For example, the oxide resistive switching based memristor is an emerging device for storage class memory and brain-inspired computing. Most of the reported memristors use the metal−insulator−metal (MIM) structures. However several works including our previous work have reported that metal−oxide−semiconductor (MOS) structure devices always exhibit diode-like current−voltage (I−V) characteristics in their low-resistance state (LRS). These devices can be defined as programmable diode (PD) and are expected to solve crosstalk problems in memory arrays. The resistive switching mechanism of PDs is attributed to the formation and breakage of oxygen vacancies (VOs) constructed conducting filaments, which is the same as MIM-structure memristors. However, the electron transport mechanisms in PDs have not been clearly explained. Revealing the underlying physics of diode-like behavior in PDs is necessary for performance optimization and circuit model development in future.
In this work, PD with structure of TiN/HfO2/Si was investigated, which is compatible with CMOS processes and exhibits stable characteristics, providing an ideal foundation for elucidating the previously unclear rectification mechanism. PDs on N-type Si with different substrate doping concentrations ND were fabricated and their I−V characteristics before and after programming were measured, as well as their area-dependence performance. Then through density functional theory (DFT) calculations, the I−V and band structure of PDs were simulated to investigate the transport mechanism. Finally, the proposed mechanism was verified by experiments.
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Junru Qu, Wentai Xia, Jifang Cao, Xueyang Li, Ran Cheng, Dong Liu, Bing Chen (2025). Transport mechanism of oxide-based programmable diode. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/25090006
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Frequently Asked Questions
What is an oxide-based programmable diode?
An oxide-based programmable diode is a device with a metal-oxide-semiconductor structure that exhibits diode-like current-voltage characteristics in its low-resistance state, which can be programmed between different resistance states. It is used to address crosstalk in memory arrays.
What is the transport mechanism in oxide-based programmable diodes?
Under forward bias, electron transport is dominated by Poole-Frenkel emission, while under negative bias, the device behaves like a reverse Schottky diode. The conduction and rectification are controlled by the interface between the oxygen vacancy filament and the semiconductor electrode.
How are oxide-based programmable diodes fabricated?
The devices are fabricated with a TiN/HfO2/Si/Al structure, which is compatible with CMOS processes. The fabrication involves depositing HfO2 on N-type silicon substrates with different doping concentrations, followed by electrode deposition.
What role do oxygen vacancies play in the operation of these diodes?
Oxygen vacancies form conducting filaments in the oxide layer, which are responsible for the resistive switching. The interface between these filaments and the semiconductor electrode controls the diode-like behavior and rectification.
Why is understanding the transport mechanism important?
Understanding the transport mechanism is crucial for optimizing device performance and developing accurate circuit models for future applications in memory and neuromorphic computing.
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