BAlGaN-based vertical cavity surface-emitting lasers operating in deep UV region
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The context of this thesis falls in the wide applications of UV light sources such as sterilization and purification. On the material aspect, III-nitrides (BAlGaInN) are promising candidates since they are chemically and physically stable with direct bandgaps covering from visible to DUV spectrum. On the structure aspect, vertical-cavity surface-emitting laser (VCSEL) is one of the most attractive configurations considering its low threshold, high efficiency, and the possibility for the integration of 2D arrays and the wafer-level tests. It constitutes a multiple-quantum-well (MQW) active region sandwiched by a top and a bottom distributed Bragg reflector (DBR). The major challenges for the VCSEL operating in deep UV region lie in the two main blocks: the emission efficiency of MQWs and the reflectivity of DBRs, which are limited by the quality of the substrates and epitaxial layers, optical-polarization properties of the MQW emission, small refractive index contrast of the layers used for DBRs at short wavelengths, etc. The work of this thesis is addressed to these problems by studying metal-organic vapor-phase epitaxy (MOVPE) growth of BAlGaN materials, developing AlGaN MQWs with enhanced surface emission and exploring BAlN/AlGaN DBRs reflecting in DUV region, for the development of optically-pumped VCSELs operating below 300 nm.