| Strained semiconductors and heterostructures have been studied for several decades, producing significant advantages over lattice matched materials for device applications. In this dissertation, two novel types of diode laser structure are studied, both which utilize, low dimensional, highly strained active regions. One device structure contains a zero-dimensional quantum confinement, quantum-dot (QD), active layer and the other consists of a highly strained two-dimensional InGaAs(N) QW structure. The growth conditions allowing for "state-of-art" self-assembled QD formation by metal-organic-chemical-vapor-deposition (MOCVD) has been established. Comprehensive studies of the resulting quantum dot device characteristics are described and remaining issues are presented. In an effort to improve three-dimensional carrier confinement to the QDs, and engineer the wetting layer, strained GaAsP, and InGaP ternary high bandgap materials are introduced, for the first time, into QD heterostructures and devices. The QD emission wavelength can be controlled up to 200 nm utilizing strained ternary barriers. An additional blue-shift of wavelength can be achieved from interdiffusing the QDs. Based on the optimization of the QD optical properties, multiple stack QD diode lasers were fabricated, and characterized. The lasing wavelengths are near 1.0-mum using ternary barriers which can be used for Er-doped fiber amplifier pump lasers. The correlation of the T0, T1 values and the extracted values of the characteristic temperature coefficients of the transparency current density, material gain, injection efficiency, and internal loss from the temperature dependent study is described. The measurement of the peak gain parameter, go, for the multiple stack structure is found to be a sensitive measure of the QD region material quality. The second aspect of study is the highly strained quantum well active region. The feasibility of emission wavelength extension with an InGaAs QW utilizing an (In)GaAsN barrier structure is proposed and a simulation study of the transition energy is undertaken. The emission wavelength can be extended utilizing InGaAsN or GaAsN barriers. To achieve 1.24 mum emitting, high power external cavity VCSELs, an InGaAsN QW VCSEL structure has been designed and the growth conditions were optimized by MOCVD. These devices hold potential for high power pump sources in frequency doubling systems, allowing for compact red sources. |
