Fabrication of low-loss, light-waveguiding, orientation-patterned semiconductor structures
Methods for the fabrication of orientation-patterned semiconductor structures are provided. The structures are light-waveguiding structures for nonlinear frequency conversion. The structures are periodically poled semiconductor heterostructures comprising a series of material domains disposed in a periodically alternating arrangement along the optical propagation axis of the waveguide. The methods of fabricating the orientation-patterned structures utilize a series of surface planarization steps at intermediate stages of the heterostucture growth process to provide interlayer interfaces having extremely low roughnesses.
1. A waveguiding, orientation-patterned semiconductor structure comprising:
a growth template comprising a first set of template domains comprising a material having a first crystalline orientation and a second set of template domains comprising the material having a second crystalline orientation, wherein the domains of the first set and the domains of the second set are disposed in a periodically alternating arrangement along the optical propagation axis of the structure;
optionally, a layer of buffer material on a top surface of the growth template, wherein the layer of buffer material comprises a first set of buffer layer domains disposed on the first set of template domains and having a first crystalline orientation and a second set of buffer layer domains disposed on the second set of template domains and having a second crystalline orientation;
a lower layer of cladding material on a top surface of the growth template or, if present, on a top surface of the layer of buffer material; wherein the lower layer of cladding material comprises a first set of lower cladding layer domains disposed on the first set of template domains or, if present, on the first set of buffer layer domains, and having a first crystalline orientation and a second set of lower cladding layer domains disposed on the second set of template domains or, if present, on the second set of buffer layer domains, and having a second crystalline orientation;
a layer of core material on a top surface of the lower layer of cladding material; wherein the layer of core material comprises a first set of core layer domains disposed on the first set of lower cladding layer domains and having a first crystalline orientation and a second set of core layer domains disposed on the second set of lower cladding layer domains and having a second crystalline orientation;
an upper layer of cladding material on a top surface of the layer of core material; wherein the upper layer of cladding material comprises a first set of upper cladding layer domains disposed on the first set of core layer domains and having a first crystalline orientation and a second set of upper cladding layer domains disposed on the second set of core layer domains and having a second crystalline orientation; and
a waveguide ridge on a top surface of the upper layer of cladding material; wherein the waveguide ridge comprises a first set of ridge domains disposed on the first set of upper cladding layer domains and having a first crystalline orientation and a second set of ridge domains disposed on the second set of upper cladding layer domains and having a second crystalline orientation;
wherein the top surface of the layer of buffer material, if present, the top surface of the lower layer of cladding material, the top surface of the layer of core material and the top surface of the waveguide ridge each have an rms roughness of no greater than 10 nm.
2. The structure of claim 1 , wherein the top surface of the layer of buffer material, if present, the top surface of the lower layer of cladding material, the top surface of the layer of core material and the top surface of the waveguide ridge each have an rms roughness of no greater than 6 nm.
3. The structure of claim 1 , wherein the top surface of the layer of buffer material, if present, the top surface of the lower layer of cladding material, the top surface of the layer of core material and the top surface of the waveguide ridge each have an rms roughness of no greater than 4 nm.
4. The structure of claim 1 , wherein the buffer material, if present, lower cladding material, core material and upper cladding material are each Group III-V semiconductor materials.
5. The structure of claim 4 , wherein the core material comprises GaAs.
6. The structure of claim 5 , wherein the lower layer of cladding material and the upper layer of cladding material comprise InGaP.
7. The structure of claim 5 , wherein the layer of buffer material is present and comprises GaAs, the lower and upper cladding materials comprise AlGaAs and the ridge material comprises GaAs.
8. The structure of claim 4 , wherein the core material comprises GaP.
9. The structure of claim 1 , wherein the layer of buffer material is present.
10. The structure of claim 1 , wherein the layer of buffer material is absent.
11. The structure of claim 1 , wherein the lower layer of cladding material, the layer of core material, the upper layer of cladding material and the waveguide ridge each have a layer thickness in the range from about 0.2 to about 6 μm.