Top-emitting surface emitting laser structures

Claim 1

In an apparatus comprising at least one electrically pumped, vertical cavity, surface emitting laser, said laser being a columnar portion of a larger layered structure constructed primarily of semiconductor material, substantially all of the layers of the said structure being continuous throughout the said columnar portion, said structure including in order, a substrate, a first multilayer dielectric mirror, an active region containing at least one layer of active gain material and a second multilayer dielectric mirror, both of said dielectric mirrors depending for reflectivity upon inclusion of a plurality of pairs of mirror layers of differing refractive index for the wavelength of laser emission, said mirrors being doped with significant impurity one such mirror region being doped p-type and the other n-type, said laser being provided with pumping means for electrically pumping active gain material to achieve lasing, said means including an electrode in electrical contact with said second multilayer dielectric mirror, said electrode being provided with an aperture permitting laser emission therethrough, characterized in that said larger structure has an electrical conductivity profile which causes current introduced into said electrode to follow a path, initially encompassing and non-enroaching on said columnar portion and subsequently encroaching on said columnar portion so that a significant part of such current passes through the said active gain region of said portion to achieve lasing, whereby laser emission passes through the said aperture, in which the said path is to a substantial extent a consequence of a buried region of increased electrical resistance, said region encompassing the said columnar portion and the said increased electrical resistance being the consequence of ion implantation damage.