Study Of InGaAs(Sb) Near-and Mid-Infrared Semiconductor Laser Materials And Devices Fabrication

Low-dimensional semiconductor quantum laser located in the1.5-2μm near-and mid-infrared wavelength range has become one of the international frontier areas. These devices are especially attractive and enormous interest for the development of the practical realization of optoelectronic devices operating in the1.5-2μm wavelength range, with potential applications in a wide variety of areas including communications, altimetry, ranging, optical sensing and monitoring.The present research work focuses on1.5-2μm quantum dots (QDs) and multiple quantum wells (MQWs) materials and devices. The active layers were in the first case low-dimensional burried In(Ga)As QDs. and in the second case MBE-grown mid-infrared antimonide MQWs In(Al)GaAsSb emitting in the1.5-2.0μm near-infrared band. By optimizing the quality of materials and the growth technology, we prepared the high quality antimonide laser structures and devices, which is conducive for further research for near-and mid-infrared semiconductor lasers development and a wide range of applications.The present research work mainly focuses on the following.First, we carried out the epitaxial growth of In(Ga)As/GaAs QDs laser material emitting in the1.5μm band, by optimizing the growth temperature, growth rate, the Ⅴ/Ⅲ beam flux, the doping concentration as well as the QDs density and shape influencing the growth quality and the photoluminescence efficiency. The addition of Sb into InGaAs decreases the strain magnitude, lengthens the wavelength. This technology also allows the optimization of the growth rate, the annealing temperature, and the effective p-type doping of the active region. We also could limit the gradient of the high-refractive index AlGaAs cladding layer and other important parameters. We analyzed the impact of the structural parameters of the optical and electrical properties of the quantum dot structure.Second, we optimized the growth conditions of InGaAs(Sb) QWs emitting in the1.5-2μm band to improve the layer quality. We also optimized the structure design of our InGaAsSb/AlGaAsSb structures, achieving high photoluminescence efficiency, significantly increasing the gain of the active region and reducing the lasing threshold. We were able to achieve highly uniform, high crystal quality InGaAsSb/AlGaAsSb devices.Third, we performed detailed materials treatment study for GaAs QD based and GaSb QW-based laser materials. To do this we solved several technological issues related to GaSb-based materials, i.e. etching, passivation and fabrication of ohmic contacts. We were then able to evaluate and characterize the devices, and analyze the threshold, efficiency and other factors. Fourth, we grew1.5-2μm wave-band low-dimensional In(Ga)As(Sb) quantum dot laser materials, as well as mid-infrared quantum well antimonide In(Al)GaAsSb lasers,i) We performed a systematic study on the growth factors affecting the quantum dots. We grew and fabricated multi-layer quantum dots-in-well laser structure (DWELL), in order to improve the uniformity of the quantum dots used as laser active region, and to increase the number of quantum dots effectively contributing to lasing. The use of multilayer quantum dot structures allows the stacking of QDs in the vertical direction via the stress interaction existing between the QD layers. An appropriate choice of the thickness of the QDs spacer layer not only increases the QDs bulk density, but also effectively improves the QD size and emission distribution uniformity. Our1.5μm wavelength multilayer lasers are able to achieve room temperature continuous lasing from20℃to60℃, with an output power as high as20mW with a1.5μm emission.ii) Using MBE growth, InGaAsSb/AlGaAsSb multiple quantum well structures were prepared with an emission wavelength located in the1.6-2.3μm range. The laser threshold current A device emitting at2.2μm wavelength was measured at187A/cm2, with a slope efficiency of0.2W/A. The maximum output power was320mW in continuous mode at room temperature. The lasing wavelength shifts with temperature by about0.28nm/℃. When the temperature is increased from20℃to60℃, the slope efficiency decreases from20.1%to10.8%.This thesis systematically studied low-dimensional In(Ga)As quantum dot, as well as MBE-grown mid-infrared antimonide quantum well In(Al)GaAsSb as laser active media. We achieved semiconductor lasing in the1.5-2μm infrared band. Our research provides a new way of thinking and effective work methods, which is of great significance for further studies related to mid-infrared semiconductor lasers applications. The methods employed and emphasized in this work proved very effective, which brings valuable results and is expected to find wide applications in the field of mid-infrared wavelength range.