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 hydrofluorice 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 (110) 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.