Selected Energy Epitaxial Deposition and Low Energy Electron Microscopy of AlN, GaN and SiC Thin Films
Abstract
The homoepitaxial growth of GaN(0001) layers was studied in situ and in real time using the low-energy electron microscope and ex situ using atomic force microscopy and transmission electron microscopy. The growth was conducted on substrates of GaN(0001) deposited on 6H-SiC(0001) by organometallic vapor phase epitaxy. Two growth techniques were employed: one with N-atoms supplied by an RF plasma source and the other with NH3 molecules seeded in a He supersonic beam. The Ga flux was supplied by an evaporative cell in both cases. Under Ga-rich conditions, non-faceted homoepitaxial layers were achieved on Ga precovered substrate surfaces for both growth methods at 665 deg C, but the growth morphologies were different. Growing GaN via gas source molecular beam epitaxy (GSMBE), where both the NH3 and Ga fluxes are known, can establish a correlation between surface morphology and the III/V ratio. The surface morphology is dependent on the III/V ratio and the film growth rate. Under N-stable conditions, increasing the Ga flux (higher III/V ratio) roughens the films until whiskers are formed. Under Ga-stable conditions, increasing the III/V ratio by reducing the ammonia flux yields smoother films, but the growth rate rapidly approaches to zero. Films containing flat hexagonal islands are produced in this limiting case. The III/V ratio does influence the growth morphology, but as reported in this paper, the III/V ratio in itself is not meaningful unless the Ga flux is specified.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1999
- Accession Number
- ADA369762
Entities
People
- H. Henry Lamb
- I. S. Tsong
- Robert F Davis
Organizations
- North Carolina State University