Schottky Contact Metallizations for GaN
Restricted (Penn State Only)
- Author:
- Clark, Jacob
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 15, 2024
- Committee Members:
- Suzanne E Mohney, Thesis Advisor/Co-Advisor
Patrick M Lenahan, Committee Member
John Mauro, Program Head/Chair
Rongming Chu, Committee Member - Keywords:
- GaN
Gallium Nitride
Atomic Layer Deposition
Schottky Barrier
Physical Vapor Deposition
Molybdenum Carbonitride
Schottky Diode
Contacts
Metal Nitrides
Metallization - Abstract:
- Schottky diodes to gallium nitride (GaN) are in demand for high-temperature, high-power applications. Optimization of the metal/semiconductor interface that constitutes a Schottky contact requires consideration of many factors, since the choice of metallization and its fabrication method can impact not only the Schottky barrier height, but also its metallurgical stability and dominant current transport mechanism(s). This work reports a thermally stable, high-performance Schottky diode with desirable rectifying characteristics prepared by atomic layer deposition (ALD), which is a route not commonly explored for contact metallization. One major effort in this thesis was to study the synthesis of molybdenum carbonitride by thermal ALD on GaN for Schottky contacts. Using a stop-flow process to overcome a nucleation delay on GaN, a 10 nm MoCxNy film was synthesized. X-ray photoelectron spectroscopy (XPS) and transmission electron spectroscopy (TEM) confirm a high-quality metal nitride/semiconductor interface. From current-voltage measurements, devices fabricated from this film had a Schottky barrier height of 0.68 ± 0.01 eV and an ideality factor of 1.06 ± 0.01. These diodes exhibit a higher barrier height and lower ideality factor than devices previously prepared by plasma enhanced atomic layer deposition (PEALD), which may have suffered from process-induced defects from the remote plasma step. After annealing the diodes at 600 ˚C, the Schottky barrier height increased to 0.82 ± 0.04 eV, and the ideality factor decreased to 1.04 ± 0.04, similar to diodes prepared by PEALD and then annealed. Likewise, capacitance-voltage measurements indicated a higher barrier height for the as-deposited thermal ALD diodes (0.66 ± 0.05 eV) compared to the PEALD diodes. After annealing, the Schottky barrier heights of the thermal ALD and PEALD diodes were similar. Through this example, the advantages and disadvantages of different approaches to ALD for diode fabrication were highlighted, which can guide future work in other materials systems. Finally, this thesis describes the fabrication of Schottky diodes using various metals deposited by physical vapor deposition and points to possible process improvements for future fabrication runs.