Evaluation of Gallium Nitride for Active Microwave Devices.
Abstract
In an attempt to minimize the high native donor density and the structural defects which lead to high field breakdown, so that high field drift velocity measurements can be made, a high pressure (10,000 atm) high temperature (1500 C) system is being set up to grow, anneal and diffuse GaN under equilibrium N2 pressures, rather than by the nonequilibrium NH3 vapor phase method currently used to prepare GaN. The system should be completely operational within 4 months. A second chemical vapor deposition apparatus designed to grow 50 micrometers crystals on R-plane sapphire at 1050 C is now working and uniform crystals are being grown routinely. Due to non-planar nucleation and growth, these crystals exhibit decorated low angle grain boundaries, some of which crack by differential thermal contraction during cool-down, and stacking faults and random small-scale precipitation in regions paralleling the linear surface topology. Light scattering from these regions colors the bulk samples. Slow growth rates eliminate the precipitated regions and tend to reduce the number of low angle boundaries and associated cracks. However, planar growth, which proceeds very slowly on (1010) sapphire or on self-nucleated whiskers eliminated virtually all these defects.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1977
- Accession Number
- ADA045419
Entities
People
- M. Gershenzon
Organizations
- University of Southern California