All-epitaxial, long-wavelength, vertical-cavity surface-emitting lasers using bipolar cascaded active region for high differential quantum efficiency

Despite the burst of the telecommunication market bubble, demands for bandwidth still seem to be growing as new applications are introduced. Optical fiber networks are capable of meeting such demand and long-wavelength vertical-cavity surface-emitting lasers (VCSELs) are attractive candidate for low cost light sources. Extensive researches resulted in dramatic improvements of the device performances with the number of different approaches such as wafer fusion, metamorphic, buried-tunnel-junction (BTJ), and all epitaxial approaches. Among them, all epitaxial VCSEL where all the components of device are grown in single growth is especially attractive for low cost application. Both DBR and the active region can be grown with AlInGaAs on InP substrate---this material system has been well developed over a couple of decade and can offer stable growth. However AlInGaAs DBR suffers from the fact that the maximum achievable reflectivity is lower than other DBRs. This can be compensated by using bipolar cascaded (BC) active region which provides higher gain. Moreover significantly higher differential quantum efficiency is achievable. The goal of this thesis was to investigate and develop practical 1.55 mu m VCSEL with cascaded active region. The scalability of BC VCSEL was investigated both theoretically and experimentally. The current confining aperture was developed using ion implantation. While continuous wave operation was not realized, the device with greater than 120% differential efficiency was demonstrated.