Nitride Semiconductors for Ultraviolet Detection.
Abstract
Monocrystalline, undoped, high resistivity GaN thin films have been grown on (6H)-SiC(0001) wafers via organometallic vapor phase epitaxy (OMVPE) employing a high-temperature monocrystalline AlN buffer layer using a cold-wall, vertical pancake-style reactor with triethylgallium (TEG), triethylaluminum (TEA) and ammonia. The surface morphologies of films deposited on both vicinal and on-axis, Si- and C-polar planes of SiC(0001) are described. Controlled n-type Si-doping in GaN has been achieved with carrier concentrations from 10(exp 17) to 10(exp 20)/ cu cm. SEM and TEM of the latter films revealed high microstructural quality Photoluminescence (PL) of the undoped GaN revealed a sharp donor-bound exciton peak at 357.2 nm with a FWHM of 4 meV. The defect peaks in these samples were very weak. The Si-doped GaN exhibited a strong PL emission at 358 nm due to donor-to-valence band transitions. Mg-doped GaN emitted strong blue light with a peak wavelength of 426 nm. Cathodoluminescence measurements of Al(x)Ga(1-x)N were also successful, with strong emission at the band-edge. An ammonia cracker cell, has also been designed and installed in the gas source MBE to replace the ECR plasma source to minimize film damage and to enhance film quality and growth rate. Low resistivity Al, Cu3Ge, and TiN ohmic contacts have been achieved on Si-doped, n-type GaN. Au and a Au/Mg/Au layered structure exhibited ohmic behavior on p-GaN when annealed at high temperature or in the as-deposited condition, respectively. As-deposited Pt formed ohmic contacts to Mg:GaN. Microstructural characterization of the Al/n-GaN and Au/p-GaN contact systems revealed that interfacial reactions occurred during annealing and markedly affected contact performance.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1994
- Accession Number
- ADA289546
Entities
People
- Bradley T. Perry
- K. Linthicum
- L. Smith
- Robert F Davis
- W. Weeks
Organizations
- North Carolina State University