Fabrication of monolithically Peltier-cooled linear laser diodes using wet chemical etching

The basic structure of a monolithically Peltier-cooled laser (MPCL) diode has been fabricated. The process of forming the structure involves critical masking and etching processes. A reliable etching process that was capable of producing clean mesas 50 µm wide × 300 µm long and of a height greater than 150-µm was developed using buffered hydrofluoric acid. The mask used-with the buffered hydro-fluorice etchant was Shipley AZ1350B photoresist. This combination of the etchant and the mask process gave good results even when etching a grid pattern consisting of an array of 2-µm-wide lines to form mesas 3.74 µm high. It was found that the etch tends to follow the cleaved planes that intersect the (100) surface at right angles to form a rectangular geometry. The etching system does not etch the photoresist mask material. Although the process was developed for the incorporation of monolithic Peltier-effect coolers for laser diodes, it is applicable to other OIC's or IC's as well.