We report on vertical-cavity surface-emitting lasers (VCSELs) fabricated using selective oxidation to form a current aperture and an oxide surface barrier to seal buried AlAs layers in distributed Bragg reflectors. The lateral selective oxidation of the AlAs layer is strongly influenced by its thickness and heterointerface structures. The oxidation rate decreases rapidly with decreasing AlAs thickness in the range of < 80 nm, and the presence of AlGaAs layers on both sides of the AlAs layer reduces the oxidation rate. In addition, an oxide surface barrier with a thickness of ∼1 µm is formed by a brief wet oxidation which blocks diffusing oxygen species during the second wet oxidation. The effectiveness of the seal is demonstrated by using the oxide barrier as a mask against wet oxidation in the fabrication of oxide-confined VCSELs. The 8×8 µm2 devices with three quantum wells exhibit a threshold current of 400 µA, and the 4×4 µm2 single-quantum devices possess a threshold current as low as 85 µA.
Si delta-doping in the GaN layer has been successfully demonstrated by metalorganic chemical vapor deposition. From the capacitance-voltage measurement, a sharp carrier concentration profile with a full width at half-maximum of 4.1 nm has been achieved with a peak concentration of 9.8×1018 cm-3. Si delta-doping concentration increases and then decreases with an increase in delta-doping time, and the use of a post-purge step in the ammonia ambient reduces Si delta-doping concentration. This indicates that delta-doping concentration is limited by the Si desorption process due to high growth temperatures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.