Oxide Aperture Shaping In Vertical Cavity Surface-Emitting Laser

Abstract

A 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 suitable 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.

What is claimed is: 
     
         1 . A vertical cavity surface emitting laser (VCSEL) comprising:
 a substrate having a top major surface;   a first distributed Bragg reflector (DBR) formed on the top major surface of the substrate, the first distributed Bragg reflector comprising a stack of layers of alternating refractive index value;   a second DBR disposed over the first DBR and comprising a stack of layers of alternating refractive index, the second DBR including a mesa structure of a predetermined cross-section geometry;   an active layer disposed between the first DBR and the second DBR; and   an aperture layer including an interior oxide aperture region created by anisotropic oxidation, the interior oxide aperture exhibiting a defined cross-section based on the predetermined cross-section geometry of the mesa structure.   
     
     
         2 . The VCSEL as defined in  claim 1  wherein the VCSEL is a GaAs-based VCSEL device. 
     
     
         3 . The VCSEL as defined in  claim 2  wherein the aperture layer comprises Al x (Ga 1-x )As, with an aluminum content x greater than aluminum content of the remaining layers of alternating refractive index value in the corrected mesa structure. 
     
     
         4 . The VCSEL as defined in  claim 3  where the aluminum content x of the aperture layer is at least about 0.90. 
     
     
         5 . The VCSEL as defined in  claim 1  wherein the predetermined shape of the mesa structure has an elliptical cross-section geometry, and the interior oxide aperture exhibits a circular cross-section geometry.