Abstract
In this thesis we first describe the difference between the edge emitting laser and the VCSEL, and we have introduced the progress of VCSELs. Since the oxide-confined VCSELs have excellent current confinement effect and many other native advantages than others, we have take our intention in the oxide-aperture current-confined VCSEL.The theories about the oxide-aperture current-confined VCSEL have been introduced. We can maintain the effective reflectance while applying different graded interfaces with different grading methods and thickness into DBR structure. We also discuss how to align the cavity resonance and gain peak for designing a structure with better performance in higher temperature. At latter we take oxide aperture placement effect and GRINSCH structure into account and finish a VCSEL structure design.Since the selective oxidation of AlGaAs layer is a key process technology of the oxide-confined VCSEL fabrication, we have taken some experiments to discuss the various about oxidation. We first demonstrate the oxidation process and equipment we used and state possible oxidation mechanism subsequently. We investigate some main variables affecting the oxidation rate just like the furnace temperature, the N2 flow rate, and the Al composition in oxide layer. Fortunately, we can obtain highly uniform oxide apertures by controlling the furnace temperature and the N2 flow rate accurately. The detail process to fabricate the oxide-confined VCSEL has been described latter. Some problems appear during the process have been discuss and improve. We have changed mesa structure from the air-post to the ring-trench. The almost same L-I curves of 4 neighboring chips show the highly stable process yield. We also have fabricated the oxide-confined VCSELs by filling Al metal into the ring trench of VCSELs, which can effectively increase the output power and enhance the high-temperature operation. The life-time test has improved the good output characteristics for these oxide-confined VCSELs.While the connecting Ti-Au metal between ohmic contact and bonding pad has to cross the 5μm–depth ring trench, it is easy to being broken during the process. We have studied some new planarized structures to improve this problem. The ring-trench structure liking a letter "C" around the mesa with a 3 μm-width bridge is the best choice. We also have demonstrated the effect of indium tin oxide as a p-type ohmic contact for the 850 nm GaAs oxide-confined VCSELs with this structure. The ITO film can be formed as a good ohmic contact without any annealing and exhibits a high optical transparency and high electrical conductivity. The oxide-confined VCSELs with ITO contact can be fabricated in a much simple photolithographic process and are more suitable to the fiber connection than the edge-emitting laser.