Aluminum Nitride (AlN), an ultrawide bandgap (UWBG) semiconductor with a bandgap of 6.1 eV, is a promising material for high-voltage and high-temperature electronic devices. In this study, researchers from the University of Tokyo (Lecturer/Assistant Prof. Maeda's group) and NTT Basic Research Laboratories (NTT) investigated current transport mechanisms in AlN-based Schottky barrier diodes (SBDs).
NTT successfully fabricated AlN SBDs with nearly ideal characteristics by employing a heavily Si-doped graded AlGaN contact layer in combination with a low-damage dry etching technique. The University of Tokyo team meticulously characterized the AlN SBDs. Using ultralow-frequency (<10 Hz) capacitance-voltage (C-V) measurements, the net donor concentration and built-in potential were precisely determined. Based on the C-V measurement results, the researchers hypothesized that thermionic field emission (TFE)—the tunneling transport of thermal electrons through the Schottky barrier—would be the dominant mechanism. The calculated TFE current showed excellent agreement with experimental data, providing strong evidence of ideal TFE transport in AlN SBDs for the first time. The Schottky barrier height and its temperature dependences were also revealed based on the C-V and I-V measurements using the analysis based on the TFE theory.
These findings represent a significant step forward in understanding and optimizing AlN-based electronic devices, paving the way for their future development in high-performance applications.
Papers
Conference: 70th IEEE International Electron Devices Meeting (IEDM 2024)
Title: Thermionic Field Emission in a Si-doped AlN SBD with a Graded n+-AlGaN Top Contact Layer
Authors: Takuya Maeda*, Yusuke Wakamoto, Issei Sasaki, Akihira Munakata, Masanobu Hiroki, Kazuyuki Hirama, Kazuhide Kumakura, Yoshitaka Taniyasu