Epitaxial Growth of Thin Films and Quantum Well Structures of Cadmium-Telluride by Molecular Beam Epitaxy.
Abstract
The heteroepitaxial growth of CdTe on alternative substrates, the application of epitaxial CdTe as a substrate for the growth of dilute magnetic semiconductor superlattices, and the in situ doping of thin film CdTe were studied. The growth of high quality (111) CdTe on (0001) sapphire was demonstrated. The best results were obtained for samples that were preheated to 925(DEGREES)C and were grown at a substrate temperature of 300(DEGREES)C. The high quality of the epilayers grown on basal plane sapphire were clearly demonstrated by the results of post-growth annealing experiments. The growth of high quality (100) CdTe/(100) GaAs was also demonstrated. The structural perfection of these epilayers was investigated using transmission electron microscopy. In the near surface region of thin films, a dislocation line density of less than 10('4) cm('-2) was found. As an application of heteroepitaxial CdTe, on either sapphire or GaAs, dilute magnetic semiconductor superlattices were grown for the first time. Cd(,1-x)Mn(,x)Te -CdTe (0 < x < 0.5) superlattices with periods from 37 A to 450 A were studied. It was found that the band gap of the superlattices could be systematically varied from 1.59 eV to 1.88 eV by varying the superlattice period. Quantum well laser structures in which either CdTe or Cd(,1-x)Mn(,x)Te served as the active region were grown and studied. Laser action in these samples was observed for the first time. Magnetic field effects on the optical properties of these structures were investigated. The in situ substitutional doping of thin film CdTe was studied using photo-assisted molecular beam epitaxy. The photo-assisted MBE technique was employed to systematically grow CdTe epilayers with carrier concentrations from 10('15) to 10('17) cm('-3) using indium as a dopant. These layers had room temperature mobilities greater than 600 cm('2)/V(.)s and increased with decreasing temperature to a peak value of 1250 cm('2)/V(.)s.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1986
- Bibcode:
- 1986PhDT........70B
- Keywords:
-
- Physics: Condensed Matter