Fabrication and characterization of GaInNAs quantum structures

Abstract

The fabrication and the structural and optical properties of bulk, quantum well, and quantum dot structures prepared of GaAsN and GaInNAs III-V compound semiconductors are studied in this thesis. Metalorganic vapor phase epitaxy is used to grow epitaxial layers on GaAs. The composition of the grown structures is investigated by x-ray diffraction. The nitrogen concentration of the GaAsN and GaInNAs layers is found to be strongly dependent on the growth temperature and the molar flow ratios of the different precursors. It is shown that an increase in the indium concentration of GaInNAs results in a decrease of the nitrogen incorporation.

Photoluminescence spectroscopy is employed to study the optical properties of the fabricated epitaxial structures. The optical quality of quantum well structures is found to decrease with increasing nitrogen concentration. However, in-situ and post-growth thermal annealing procedures as well as post-growth laser treatment are investigated and used to improve the optical properties. Luminescence wavelengths of up to 1.55 μm are observed from GaInNAs quantum well structures.

The effect of nitrogen on the optical properties of various self-assembled quantum dot structures is studied. The surface morphology of these structures is investigated by atomic force microscopy. Although the incorporation of nitrogen into GaIn(N)As quantum dots is found to be negligible, the size and the areal density of the self-organized GaIn(N)As islands can be controlled and the optical properties improved by varying the nitrogen precursor flow. It is found that the luminescence wavelength and intensity of GaInAs quantum dots in the 1.3 μm wavelength range can be increased by embedding the islands in a GaInNAs barrier layer. Also strain-induced GaInNAs quantum dots are fabricated using InP islands as stressors.