Doctoral Thesis: Vacuum Transistors Based on III-Nitrides Self-Aligned-Gate Field Emitter Arrays

Pao-Chuan Shih

Abstract:

      Vacuum electronics are promising future high-frequency and harsh-environment devices because of their scattering-free and radiation-robust vacuum channels. Field-emission vacuum transistors based on silicon and metals have been demonstrated in past 30-40 years, while the power consumption and long-term device stability are still issues. To further improve field-emission devices, III-Nitride semiconductors are attracting attentions recently thanks to their engineerable electron affinities and high bonding energies. Instead of potentials of III-Nitride vacuum transistors, there were still limited transistor-level demonstrations with comparable performance. 

      This thesis identifies the key challenges of III-Nitride vacuum transistors and demonstrates our approaches to tackle them. Three key building blocks, such as (1) self-aligned-gate structure, (2) technology to form sharp and uniform field emitter tips, and (3) integrated anode, are developed in this thesis research.  First, self-aligned-gate structures are developed on GaN field emitter arrays formed by the top-down approach. The transistor-like behavior is achieved, and the operating voltages are reduced. Second, the performance of field-emission-based vacuum transistors is further improved by modifying the device structures and by developing the new digital etching technology to form uniform and sharp emission tips. Our latest GaN devices show better performance than the state-of-the-art Si devices at the same bias condition. Finally, the structure and corresponding fabrication of the integrated anode are discussed and demonstrated with preliminary experiments. The three building blocks developed in this thesis research serve as the foundations of the future compact and energy-efficient III-Nitride vacuum transistors for circuit-level demonstrations and high-frequency, high-power, and harsh-environment applications.

Thesis Committee:

Prof. Tomas Palacios (Thesis Supervisor)

Prof. Akintunde I. Akinwande

Prof. Karl Berggren

Details

• Date: Wednesday, June 14
• Time: 1:00 pm - 2:30 pm
• Category: Thesis Defense
• Location: 34-401A

Additional Location Details:

To attend via Zoom

Link: https://mit.zoom.us/j/93295949072?pwd=MC9ocXRNZ3AwYUNXdjNnUzdwUE9xQT09

Zoom meeting ID: 932 9594 9072

Zoom Password: GaN-FEA