Growth of Aluminum Gallium Nitride Thin Films for Electro-Optic Device Applications.
Abstract
Highly p-doped (AlGa)N offers the prospect of very efficient and sharp-cutoff solar-blind photocathodes, as well as near-UV solid-state lasers. However, AlN reported to date has been semi-insulating, and GaN has been semi-insulating or n-type. Spontaneous generation of compensating N-vacancy donors is believed responsible for the inability to p-dope GaN. In this work, GaN was deposited on sapphire by reaction of Ga with a high-pressure (100 Pa) N2 plasma over the substrate. High plasma pressure and low substrate temperature were used in order to inhibit N-vacancy formation. Be, a likely and low-volatility p-dopant, was co-deposited. After it proved impractical to introduce Ga into the N2 plasma by evaporation, it was sputtered in a 100 Pa DC N2 plasma with much better success. Epitaxy of updoped films was obtained at 700 C, although films doped to 4 - 6 x 10 to the 20th power Be/cc were polycrystalline. All films turned out n-type by thermoelectric probing and exhibited a large activation energy for conduction, indicating the dominance of unintentional deep impurities. Undoped films had resistivities of 400,000 ohm-cm at 300 C and 20,000 ohm-cm at 600 C. Be doping increased conductivity by X100 and appeared to be acting as a deep donor. A cleaner sputtering environment and closer Be control are recommended in the further pursuit of p-type GaN. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 15, 1981
- Accession Number
- ADA099517
Entities
People
- Donald L. Smith
- Richard H. Bruce