TABLE OF CONTENTS Most of the post-growth fabrication issues of importance in making electronic devices are equally applicable in making optoelectronic devices. Many of the performance characteristics are grown in by the specific design of mirror stacks, quantum-well numbers and thicknesses, dopant profile distributions, etc. Post-growth processing, with the exception of wet oxidation, is generally the same as that of electronic devices. The previous chapters in this book dealing with cleaning, passivation, etching and contact formation address the main requirements for fabricating optoelectronic devices. The details of the technique of regrowth, which involves etching a structure into a wafer and introducing it again into a growth chamber for deposition of additional semiconductor layers on the textured substrate, are beyond the scope of this book. To fabricate top-surface gratings for a DFB (distributed feedback) laser, proper mask alignment relative to the crystal axes and crystallographic etching can be used to form the grating, as discussed in Section 4.3.2. Crystallographic etching can also be used to form smooth, vertical mirrors with proper alignment of the mask relative to a wafer's crystal planes.
Because the principal additional fabrication technique for optoelectronic devices is the wet oxidation of buried Al-containing layers to make current apertures in VCSELs (vertical cavity surface emitting lasers), this chapter will focus on that process. Both fundamental issues and practical considerations for using a wet oxidation process are presented here. The chapter concludes with a discussion of attempts to make electronic devices, such as GaAs-on-insulator (GOI) MESFETs and metal-insulator-semiconductor (MIS)...
