Self-passivation reduces the Fermi level pinning in the metal-semiconductor contacts

TL;DR

This study reveals that self-passivation of dangling bonds at metal-semiconductor interfaces significantly reduces Fermi level pinning, thereby potentially lowering contact resistance in semiconductor devices.

Contribution

It demonstrates that self-passivation of interface dangling bonds can effectively reduce Fermi level pinning in metal-semiconductor contacts, offering new strategies for contact engineering.

Findings

Self-passivation reduces interface gap states and weakens FLP.

Reconstructed bonding configuration influences pinning factors.

Full passivation can increase pinning factor to 0.5.

Abstract

The metal-induced gap states (MIGS) are commonly believed to cause the strong Femi level pinning (FLP) in the metal-semiconductors contacts. Here, we unravel unambiguously that the dangling bonds-induced interface states play a crucial role, even comparable with MIGS. The first-principles calculations show that metal-Ge and metal-Si contacts should possess a similar FLP strength if they adopt an identical interface bonding configuration: the reconstructed bonding configuration renders Si and Ge having pinning factors of 0.16 and 0.11, respectively, and the ideal non-reconstructed bonding configuration gives them pinning factors of 0.05 and 0, respectively. We illustrate that Si favors the reconstructed bonding configuration, and Ge favors the ideal non-reconstructed bonding configuration after metal deposition. The self-passivation of the dangling bonds substantially reduces the interface gap states to give a much weaker FLP in the metal-Si contacts than in the metal-Ge contacts. We also demonstrate that the full passivation of the interface dangling bonds can further increase the pinning factor to 0.5 by further reducing the interface gap states. These findings shed new light on alleviating the Femi level pinning to lower the contact resistance for Si and emerging materials towards advanced semiconductor technology.