A method for the reuse of gallium nitride (GaN) epitaxial substrates uses band-gap-selective photoelectrochemical (PEC) etching to remove one or more epitaxial layers from bulk or free-standing GaN substrates without damaging the substrate, allowing the substrate to be reused for further growth of additional epitaxial layers. The method facilitates a significant cost reduction in device production by permitting the reuse of expensive bulk or free-standing GaN substrates.

A method for the reuse of gallium nitride (GaN) epitaxial substrates uses band-gap-selective photoelectrochemical (PEC) etching to remove one or more epitaxial layers from bulk or free-standing GaN substrates without damaging the substrate, allowing the substrate to be reused for further growth of additional epitaxial layers. The method facilitates a significant cost reduction in device production by permitting the reuse of expensive bulk or free-standing GaN substrates.

A laser structure comprising a first photonic crystal surface emitting laser (PCSEL), a second PCSEL, and a coupling region that extends between the first PCSEL and the second PCSEL along a longitudinal axis and that is electrically controllable so as to be capable of coherently coupling the first PCSEL to the second PCSEL. Each PCSEL include an active layer, a photonic crystal, and a two-dimensional periodic array distributed in an array plane parallel to the longitudinal axis within the photonic crystal where the two-dimensional periodic array is formed of regions having a refractive index that is different to the surrounding photonic crystal.

A laser structure comprising a first photonic crystal surface emitting laser (PCSEL), a second PCSEL, and a coupling region that extends between the first PCSEL and the second PCSEL along a longitudinal axis and that is electrically controllable so as to be capable of coherently coupling the first PCSEL to the second PCSEL. Each PCSEL include an active layer, a photonic crystal, and a two-dimensional periodic array distributed in an array plane parallel to the longitudinal axis within the photonic crystal where the two-dimensional periodic array is formed of regions having a refractive index that is different to the surrounding photonic crystal.

A surface emitting quantum cascade laser includes an active layer, a first semiconductor layer, and first electrode. The active layer has a plurality of quantum well layers stacked therein. The active layer is capable of emitting laser light by inter-subband transition. The first semiconductor layer is provided on the active layer and having a first surface provided with a plurality of pits so as to constitute a two-dimensional lattice. The first electrode is provided on the first semiconductor layer and having a periodic opening. Each pit is asymmetric with respect to a line parallel to a side of the lattice. The laser light is emitted in a direction generally perpendicular to the active layer from a pit exposed to the opening.

A surface-emitting laser array and a laser device including the surface-emitting laser array. The surface-emitting laser array includes a layered product including a lower reflecting mirror having two layers with different refractive indexes, an upper reflecting mirror, and an active layer disposed between the lower reflecting mirror and the upper reflecting mirror, a first separation trench from which the upper reflecting mirror, the active layer, and the lower reflecting mirror are removed, the first separation trench separating the surface-emitting laser array from an adjacent chip, and a second separation trench disposed between the first separation trench and a light-emitting unit that emits a laser beam, the second separation trench having a prescribed depth.

A surface-emitting laser array and a laser device including the surface-emitting laser array. The surface-emitting laser array includes a layered product including a lower reflecting mirror having two layers with different refractive indexes, an upper reflecting mirror, and an active layer disposed between the lower reflecting mirror and the upper reflecting mirror, a first separation trench from which the upper reflecting mirror, the active layer, and the lower reflecting mirror are removed, the first separation trench separating the surface-emitting laser array from an adjacent chip, and a second separation trench disposed between the first separation trench and a light-emitting unit that emits a laser beam, the second separation trench having a prescribed depth.

A method for fabricating a surface emitting laser includes the steps of: preparing an epitaxial substrate including a substrate and a laminate disposed on the substrate, the laminate including a Bragg reflector and an active layer; forming a mask for defining a semiconductor post on the epitaxial substrate; after forming the mask, placing the epitaxial substrate in an etching apparatus with an end point detector including an optical device; carrying out plasma etching of the epitaxial substrate by supplying a gas including boron chloride and chlorine in the etching apparatus; and stopping the plasma etching in response to an end point detection from the end point detector of the etching apparatus. The optical device of the end point detector detects an end point of a process through a viewport of the etching apparatus. The plasma etching is carried out in a process pressure of one Pascal or less.

A method for fabricating a surface emitting laser includes the steps of: preparing an epitaxial substrate including a substrate and a laminate disposed on the substrate, the laminate including a Bragg reflector and an active layer; forming a mask for defining a semiconductor post on the epitaxial substrate; after forming the mask, placing the epitaxial substrate in an etching apparatus with an end point detector including an optical device; carrying out plasma etching of the epitaxial substrate by supplying a gas including boron chloride and chlorine in the etching apparatus; and stopping the plasma etching in response to an end point detection from the end point detector of the etching apparatus. The optical device of the end point detector detects an end point of a process through a viewport of the etching apparatus. The plasma etching is carried out in a process pressure of one Pascal or less.

A semiconductor light-emitting element has a distributed Bragg reflector that is grown by depositing an InAlN layer and a GaN layer a plurality of times in that order on a semipolar plane of a semiconductor substrate, and a semiconductor structure layer that is formed on the distributed Bragg reflector and includes an active layer. The InAlN layer has a plurality of projections on an interface with the GaN layer, and the InAlN layer has a low In region which is formed at the top of each of the plurality of projections and which is lower in In composition than the remaining region.