| Long-wavelength vertical cavity lasers (VCLs) can be an excellent source for fiber-optic telecommunications transmitters, thanks to their small footprint, ease of manufacturing, wafer scale testing, optical fiber coupling efficiency, and direct modulation bandwidth. Several approaches to realizing long-wavelength VCLs at both important telecommunications wavelengths, 1310 nm and 1550 nm, have been tried, including GaInNAs-based GaAs lasers and wafer bonded AlGaAs/InP structures. Both efforts are geared towards overcoming a traditional shortcoming of InP-based VCLs: the lack of high index-contrast distributed Bragg reflector (DBR) mirrors that can be grown lattice-matched to the substrate. Previously we had demonstrated 1550 nm VCLs grown via molecular beam epitaxy (MBE) which used AlGaAsSb alloys as the DBR material, and which laced up to 88°C with greater than 1mW output power at room temperature and 23% differential quantum efficiency. Devices operating at 1310 nm are now desired, to demonstrate the flexibility of this technology platform. In this dissertation the materials growth optimization for these associated alloys is described; in particular, the growth diagram for InP is defined. Interfaces between the various alloys of AlGaAsSb, AlInGaAs, and InP are explored and optimized to reduce defect density and roughness. Active region design and optimization for both 1310 nm and 1550 nm emission is presented as well. Aperture design to reduce optical scattering losses as low as possible is also outlined, with conclusions for optimum aperture thickness and placement. A tunnel junction was used as the aperture for our 1310 run VCLs, to combine optical and current confinement into one layer. This thin (35 nm) tunnel junction was then selectively etched with respect to the surrounding InP cladding, forming an air-gap aperture with ultra-low loss. A 1310 nm VCL grown using optimized MBE methods and interfacial transitions and processed to include the thin tunnel junction apertures yielded outstanding performance. Maximum power at room temperature was 2.2 mW for multimode devices, and 1.4 mW single mode. Maximum operating temperature was 90°C, with a threshold current near 1 mA. Differential quantum efficiency was observed as high as 64%, a record for all long-wavelength vertical cavity lasers. |
