Method for forming an optoelectronic device having an isolation layer
View Patent ↗Methods are disclosed for forming optoelectronic devices. In one example of such a method, a substrate is provided and a partially conductive bottom mirror formed thereon. An active region is then formed on the bottom mirror, and a top mirror formed on the active region. A gain guide is then formed in the top mirror. Finally, a substantially dielectric isolation layer, as well as a resonant reflector, are formed on the top mirror. The isolation layer is interposed between the resonant reflector and the top mirror, and the isolation layer is formed so as to substantially prevent energy in an evanescent tail of a guided mode associated with the resonant reflector from entering the top mirror.
1. A method for forming an optoelectronic device, comprising:
forming a substrate;
forming a bottom mirror on the substrate, the bottom mirror being at least partially conductive;
forming an active region above the bottom mirror;
forming a top mirror above the active region, the top mirror being at least partially conductive;
defining a gain guide aperture in the top mirror; and
forming, above the top mirror, a substantially dielectric isolation layer, and a resonant reflector, the substantially dielectric isolation layer being interposed between the resonant reflector and the top mirror, and the substantially dielectric isolation layer being formed so as to substantially prevent energy in an evanescent tail of a guided mode associated with the resonant reflector from entering the top mirror.
2. The method as recited in claim 1 , wherein the top mirror and bottom mirror are Distributed Bragg Reflector mirrors.
3. The method as recited in claim 2 , wherein the Distributed Bragg Reflector mirrors include alternating layers of AlGaAs and AlAs.
4. The method as recited in claim 1 , wherein a top layer of the top mirror substantially comprises AlGaAs.
5. The method as recited in claim 1 , wherein the ability of the substantially dielectric isolation layer to substantially prevent energy in the evanescent tail of the guided mode associated with the resonant reflector from entering the top mirror results from at least one of: the substantially dielectric isolation layer being formed of a material having a refractive index that is sufficiently low, relative to a refractive index associated with the resonant reflector; and, the substantially dielectric isolation layer being sufficiently thick.
6. The method as recited in claim 1 , wherein the substantially dielectric isolation layer comprises one of: a cladding layer; or, a buffer layer.
7. The method as recited in claim 1 , wherein the substantially dielectric isolation layer initially substantially comprises AlGaAs, which is subsequently oxidized to AlO.
8. The method as recited in claim 7 , wherein the substantially dielectric isolation layer is substantially laterally oxidized.
9. The method as recited in claim 1 , wherein defining the gain guide aperture in the top mirror comprises one of: implementing an H+ ion implant in the top mirror; implementing gain-guided current and field confinement in the top mirror; and, implementing oxide-confinement in the top mirror.
10. The method as recited in claim 1 , wherein the substrate comprises a VCSEL-structure substrate, and the resonant reflector is formed so as to be one of: substantially reflective for the VCSEL-structure substrate; or, substantially non-reflective near an emission wavelength for the VCSEL-structure substrate.
11. The method as recited in claim 1 , wherein forming the resonant reflector comprises:
providing a waveguide;
providing a grating film adjacent the waveguide; and
etching the grating film to form at least two spaced grating regions separated by at least one spaced etched region, the at least one spaced etched region extending to a depth that produces a desired optical property for the resonant reflector but not extending all the way through the grating film.
12. The method as recited in claim 11 , wherein the waveguide substantially comprises GaAs.
13. The method as recited in claim 11 , wherein the grating is formed by etching an SiO 2 film.
14. The method as recited in claim 11 , wherein the waveguide and grating are formed such that a first-diffraction order wave vector of the grating substantially matches a propagating mode of the waveguide.
15. The method as recited in claim 11 , wherein a refractive index of the waveguide is higher than an average refractive index of the grating.
16. The method as recited in claim 11 , wherein the waveguide includes a first dielectric and the substantially dielectric isolation layer includes a second dielectric layer having a refractive index that is less than a refractive index of the first dielectric.