Oxide aperture shaping in vertical cavity surface-emitting laser
A corrected mesa structure for a VCSEL device is particularly configured to compensate for variations in the shape of the created oxide aperture that result from anisotropic oxidation. In particular, a corrected mesa shape is derived by determining the shape of an as-created aperture formed by oxidizing a circular mesa structure, and then ascertaining the compensation required to convert the as-created shape into a desired (“target”) shaped aperture opening. The compensation value is then used to modify the shape of the mesa itself such that a following anisotropic oxidation yields a target-shaped oxide aperture.
1. A method of creating an oxide aperture of a predetermined target cross-sectional shape within a mesa structure of a vertical cavity surface emitter laser (VCSEL) device, the method including the steps of:
a) defining a target oxide aperture shape r oxap (θ);
b) performing oxidation of a test VCSEL mesa structure having an initial mesa shape r mesa (θ);
c) determining a shape d oxap (θ) of an as-fabricated oxide aperture resulting from the oxidation of step b);
d) measuring a difference between the target oxide aperture shape r oxap (θ) and the as-fabricated shape d oxap (θ) at various radial locations to create a radial deviation function Δ(θ); and
e) adding the deviation function Δ(θ) to the initial mesa shape r mesa (θ) to define a corrected mesa shape c mesa (θ); and
f) etching the VCSEL device to exhibit the corrected mesa shape.
2. The method as defined in claim 1 , further comprising the step of:
oxidizing the corrected mesa shape structure to form the oxide aperture of the predetermined target cross-sectional shape.
3. The method as defined in claim 1 wherein the target oxide aperture is circular in cross-sectional shape.
4. The method as defined in claim 1 , wherein in performing step d), if the radial deviation function Δ(θ) is less than a defined threshold value, eliminating the performance of steps e) and f).