GaSb-based Type-I InGaAsSb/AlGaAsSb Quantum Wells and Their Applications to Mid-Infrared Lasers

• Main Authors: Lin, Chien-Hung, 林建宏
• Other Authors: Lee, Chien-Ping
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/17504636723201491616

博士 === 國立交通大學 === 電子工程學系 電子研究所 === 103 === In this dissertation we studied the growth and material properties of GaSb-based type-I InGaAsSb/AlGaAsSb quantum wells (QWs) and their applications to mid-infrared (mid-IR) opto-devices. We developed a molecular beam epitaxy (MBE) growth technique that could greatly improve the optical qualities of the QWs. By controlling the group-V elements at interfaces during growth, we were able to achieve high quality QWs free from undesired localized trap states, which might otherwise severely affect the exciton recombination. Strong and highly efficient exciton emissions up to room temperature (RT) with a wavelength of 2.2 m were observed. A comprehensive investigation on the QW quality was carried out using temperature dependent and power dependent photoluminescence (PL) measurements. The PL emission intensity remained nearly constant at low temperatures and was free from the PL quenching from the defect induced localized states. The temperature dependent emission energy had a bulk-like behavior, indicating high quality well/barrier interfaces. Because of the uniformity of the QWs and smooth interfaces, the low temperature limit of inhomogeneous line width broadening was as small as 5 meV. Based on the high quality QWs obtained by the above mentioned technique, we developed two types of mid-IR laser devices in this Sb-based material system. One is a dual wavelength laser and the other is a photonic crystal surface emitting laser (PCSEL). For the dual wavelength lasers, two kinds of InGaAsSb/AlGaAsSb QWs with different compositions were grown as the active region in a single waveguide laser structure. A proper barrier was added in the structure to isolate the two well sections. Two wavelength emissions at 2.31 m and 2.61 m were obtained at RT by optical pumping (the wavelength difference is up to 300 nm). When the cavity length is properly chosen, both wavelengths reach the threshold simultaneously. Second, we demonstrated above RT optically pumped GaSb-based mid-IR PCSELs. The lasers emitted at a wavelength of ~ 2.3 m with a line width of 0.3 nm and a threshold power density of ~ 0.3 kW/cm2 at RT. The square lattice photonic crystal (PC) on the surface provides the optical feedback for laser operation and light coupling for surface emission. The PCSELs were operated with temperatures up to 350 K, showing a small wavelength shift rate of 0.21 nm/K. The PCSELs with different PC etching depth were studied and simulated. As optical field couples more into the PC region due to the increase of etching depth, both the lasing wavelength and the threshold power density decrease. The calculations could fit well with the experimental results.