Soutenance de thèse / PhD Defense - Yimin Zhang

Yimin Zhang, doctorante dans l'équipe Minéralogie et magnétisme de basses dimensionnalités (MIMABADI) soutient sa thèse le vendredi 28 juin à 14 h.

Sorbonne Université - Campus P. et M. Curie - 4 place Jussieu - 75005 PARIS - Barre 22-23 - 3e étage - salle 317

Modulating Metal-Semiconductor Schottky effect with electrostatic doping : Au-InSe as a case study

Abstract

This thesis presents an in-depth analysis of the Schottky Barrier Height (SBH) in metal/indium selenide (InSe) contacts and explores the modifications to contact characteristics through electrostatic doping within a Schottky diode framework. The study begins by investigating the influence of doping on SBH in metal/InSe junctions using gold (Au), aluminum (Al), and silver (Ag) as contact metals. It was found that Au contacts did not form ideal Schottky barriers, showing signs of resistive leakage, while Al and Ag contacts demonstrated quasi-linear behavior with significant resistances and stability issues, respectively.

Further exploration revealed that varying metal contacts or using asymmetric configurations had minimal impact on improving the I-V characteristics, which were predominantly resistive and slightly non-linear. This behavior suggests non-ideal interface conditions, potentially due to defects and metal-induced gap states. The two-way parallel diodes model was effective in fitting I-V curves, reflecting the complexities at the metal semiconductor interface and allowing for the extraction of key parameters, such as the non-saturating current behavior at elevated voltages.

A notable observation across different metal contacts is the consistent SBH of around 0.5 eV, indicating a Fermi level pinning phenomenon that overrides individual metal characteristics. Despite attempts at electrostatic doping, only minor changes in SBH were observed, underscoring the challenges posed by Fermi level pinning by metal-induced gap states, particularly with Au contacts.

The research progresses to optimizing electronic interfaces for Schottky diodes by targeting ohmic behavior through selective doping and device geometry, which confines electrostatic space charge doping. This involves a significant Fermi level shift, essential for depinning at targeted junctions to achieve ohmic contacts. The culmination of this work is demonstrated in devices that exhibit true Schottky rectifying behavior, highlighted by a substantial increase in current due to doping-induced mechanisms, although leading to rapid device failure under extreme conditions.

Overall, the thesis advances the understanding of SBH in metal/InSe junctions and contributes novel approaches to achieving optimized Schottky diodes through precise control of doping and device architecture.

Jury

• Mme Nedjma Bendiab (Université Grenoble Alpes) Reviewer
• M. Alberto Zobelli (Université Paris Saclay) Reviewer
• M. Massimiliano Marangolo (Sorbonne Université) Examiner
• M. Abhay Shukla (Sorbonne Université) Director
• M. Johan Biscaras (Sorbonne Université) Co-Advisor (invited)