Researchers from the University of Lille, CNRS, IEMN, and the Institute of High Pressure Physics in Warsaw have published a study comparing the reverse current mechanisms in gallium nitride (GaN) Schottky diodes grown on different substrates. The study, titled “Comparison of reverse current mechanisms in GaN Schottky diodes grown on sapphire versus ammonothermal GaN substrates,” was published in the journal Applied Physics Letters.
Gallium nitride (GaN) is a semiconductor material widely used in high-power and high-frequency electronic devices. Schottky barrier diodes (SBDs) made from GaN are crucial components in these devices, but their performance can be affected by leakage currents, which are unwanted currents that flow in the reverse direction. Understanding the mechanisms behind these leakage currents is essential for improving the efficiency and reliability of GaN-based devices.
The researchers analyzed the reverse current mechanisms in GaN SBDs grown on two different substrates: sapphire and native GaN. They found that the diodes grown on sapphire substrates exhibited two distinct conduction mechanisms: Poole-Frenkel emission (PFE) and trap-assisted tunneling (TAT). PFE is a process where electrons are emitted from traps within the material, while TAT involves electrons tunneling through these traps. The trap energy levels associated with these mechanisms were found to be 0.9 eV and 0.3 eV, respectively.
In contrast, the GaN-substrate sample showed only PFE, with a trap energy of 0.75 eV. The absence of TAT in the GaN-substrate sample suggests that this mechanism is related to the higher dislocation density in structures grown on sapphire substrates. Dislocations are defects in the crystal structure that can act as traps for electrons, facilitating TAT.
The researchers extracted the leakage mechanisms and associated trap energies by comparing experimental current-voltage (I-V) characteristics with a model that includes thermionic emission and tunneling contributions for different temperatures, ranging from 298K to 443K. Thermionic emission is a process where electrons are emitted over the potential barrier of the Schottky contact, while tunneling involves electrons passing through the barrier.
This study provides valuable insights into the leakage current mechanisms in GaN SBDs, which can guide the development of more efficient and reliable GaN-based devices. By understanding and controlling these mechanisms, engineers can design devices with lower leakage currents, leading to improved performance and energy efficiency in the energy sector. This research was published in the journal Applied Physics Letters.
This article is based on research available at arXiv.