1.55-μm InP-lattice-matched VCSELs with AlGaAsSb-AlAsSb DBRs

In this paper, we review the design, fabrication, and characterization of 1.55-mum lattice-matched vertical-cavity surface-emitting lasers, operating continuous wave up to 88 degreesC. For one embodiment, the threshold current is 800 muA, the differential quantum efficiency is 23%, and the maximum output power is more than 1 mW at 20 degreesC and 110 muW at 80 degreesC. The basic structure consists of AtAsSb-AlGaAsSb mirrors, which provide both high reflectivity and an InP-lattice-matched structure. The quaternary mirrors have poor electrical and thermal conductivities, which can raise the device temperature. However, a double-intracavity-contacted structure along with thick n-type InP cladding layers circumvents these drawbacks and finally leads to an excellent performance. The measured voltage and thermal impedances are much lower for the intracavity-contacted device than an air-post structure in which current is injected through the Sb-based quaternary mirror. The structure utilizes an undercut aperture for current and optical confinement. The aperture reduces scattering loss at the etched mirror and contributes to high differential efficiency and low threshold current density.