1.55-μm-Range Vertical-Cavity Surface-Emitting Lasers, Manufactured by Wafer Fusion of Heterostructures Grown by Solid-Source Molecular-Beam Epitaxy

Abstract

The results are presented of a study and optimization of the conditions under which heterointerfaces of the GaAs–InGaAsP type are formed via the direct intermolecular wafer bonding (fusion) of a heterostructure of an active region on an InP substrate and distributed Bragg reflectors on GaAs substrates upon the fabrication of hybrid heterostructures for long-wavelength vertical-cavity surface-emitting lasers (VCSELs). The heterostructures are grown by solid-source molecular-beam epitaxy. It is shown that, in the case of the incomplete removal of oxide films during preparation of the wafers before fusion and/or in the presence of adsorbed water on the wafer surfaces, the fused interface contains a large number of amorphous inclusions, which are most likely oxides of Group-III elements. Optimization of the conditions in which a buried tunnel junction is formed on the surface of the heterostructure on an InP wafer made it possible to reduce the surface roughness to 1 nm and to ensure that the thickness of the GaAs–InGaAsP fused interface does not exceed 5 nm, with no dislocations or other extended defects found at the fused heterointerfaces. The 1.55-μm VCSELs fabricated from the hybrid heterostructures created using the developed technology demonstrate efficient lasing under continuous-wave pumping in a wide temperature range, which is indicative of the high optical quality of the fused heterointerfaces in the VCSEL structure.