Date of Graduation

2005

Document Type

Thesis

Degree Type

MS

Committee Chair

Dimitris Korakakis

Abstract

Vertical-cavity surface-emitting lasers (VCSELs) operating at long wavelength (1.3-1.55 µm) are of great interest as inexpensive, high-performance light sources for optical communication systems. Surface emission and the small dimensions of the laser cavity are advantageous for on-chip testing, packaging, effective fibre coupling and potential low-cost fabrication. Long wavelength operation is favorable in fiber optic communications because of efficient transmission of data in silica fibres at that wavelength. However, when compared to GaAs-based VCSELs operating at wavelengths below 1000nm, which have seen a tremendous development in recent years, the progress for the long-wavelength devices has been much slower. The limited refractive index contrast between InP and GaInAsP is of specific importance, impeding the fabrication of an all-epitaxial device structure with two monolithically integrated semiconductor distributed Bragg reflectors (DBRs) as it is common for GaAs-based VCSELs. For this reason, there is a strong interest in monolithic devices, i.e., devices that can be grown entirely on InP-substrate in a more inexpensive process. In our thesis we introduced a new material system GaAsN/AlAsN with dilute nitrogen for long wavelength VCSELs. Because of the properties of dilute nitride compounds it can be used for the long wavelength operations. Because of the property of the GaAsN band gap bowing with addition of nitrogen we could able to get a material with short band gap which can be used for long wavelengths. As AlAs is also from same family (III-V) we assumed it also behaves like GaAsN and proceeded with our calculations for getting good index contrast pair. Finally by using 4% of nitrogen we theoretically shown we may be able to get good contrast high reflectivity and lattice matched to dilute nitride based cavity region DBRs for long wavelengths. The nitrogen concentration is kept uniform in order to avoid interdiffusion between the layers and between the cavity and mirrors. The lattice mismatch between the layers is observed to be in the desirable range.

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