Buried heterostructure device having integrated waveguide grating fabricated by single step MOCVD
View Patent ↗The device is an optoelectronic device or transparent waveguide device that comprises a growth surface, a growth mask, an optical waveguide core mesa and a cladding layer. The growth mask is located on the semiconductor surface and defines an elongate growth window having a periodic grating profile. The optical waveguide core mesa is located in the growth window and has a trapezoidal cross-sectional shape. The cladding layer covers the optical waveguide core mesa and extends over at least part of the growth mask. Such devices are fabricated by providing a wafer comprising a growth surface, growing an optical waveguide core mesa on the growth surface by micro-selective area growth at a first growth temperature and covering the optical waveguide core mesa with cladding material at a second growth temperature, lower than the first growth temperature.
1. A device fabrication method, comprising:
providing a growth chamber;
providing a wafer;
growing a cladding layer on the wafer, an exposed surface of the cladding layer defining a growth surface;
forming a growth mask on the growth surface, the growth mask defining an elongate growth window having a periodic grating profile and in the growth chamber, performing a fabrication process, comprising:
growing an optical waveguide core mesa on the growth surface by micro-selective area growth, and
without removing the wafer from the growth chamber after the fabricating, covering the optical waveguide core mesa with cladding material extending over at least part of the growth mask to form another cladding layer.
2. The method of claim 1 , in which forming the growth mask with the periodic grating profile creates a refractive index difference in the optical waveguide core mesa.
3. The method of claim 2 , in which:
the growth surface has a [100] crystalline orientation; and
the forming comprises aligning opposed edges of the growth mask parallel to the [011] crystalline direction of the growth surface.
4. The method of claim 2 , in which the fabrication process lacks an etching process performed after completion of the forming and before completion of the covering.
5. The method of claim 1 , in which:
the optical waveguide core mesa comprises sloped sidewalls and a top surface extending between the sidewalls;
the growing comprises growing the optical waveguide core mesa at a growth temperature above that at which adatoms migrate from the sidewalls to the top surface of the optical waveguide; and
the covering comprises growing the cladding material at a growth temperature below that at which adatoms migrate off the side walls of the optical waveguide core mesa.
6. The method of claim 5 , in which the covering comprises growing the cladding material laterally over part of the growth mask.
7. The method of claim 1 , in which the covering comprises growing the cladding material under growth conditions in which the cladding material grows on the sidewalls of the optical waveguide core mesa in addition to the top surface thereof.