METHOD OF MANUFACTURING AN OPTOELECTRONIC SEMICONDUCTOR DEVICE COMPRISING A MESA

摘要

An optoelectronic device, such as a laser of the ridge waveguide type, can be provided with the necessary mesa (14) by means of wet or dry etching with a mask (20). The etching process is stopped when an etching stopper layer (5) is reached. A laser obtained by wet etching is indeed least expensive, but it is found to have a kink in its power-current characteristic at an undesirably low power value. According to the invention, such a laser must be manufactured in that the mask (20) used is given a width which is (much) greater than the width desired for the mesa (14), and in that, after a (preferably wet) etching process down to or down to close to the etching stopper layer (5), etching is continued with a wet isotropic etchant which is selective relative to the etching stopper layer (5) until the mesa (14) formed has the desired width. A very narrow and steep mesa (14) can thus be realized in an inexpensive manner. It is found that a laser with such a mesa (14) does not exhibit the kink mentioned above until at a comparatively high power. When used in the GaAs/A1GaAs material system, the invention results in a laser which is highly suitable for use as a writing laser in a system for optical registration, or as a pumping laser in a system for glass fiber communication. The two etching steps mentioned may be carried out with one and the same wet etchant, for example an etchant based on C6H8O7 (citric acid) in the case of the GaAs/A1GaAs material system. It is alternatively possible, for example, to use two etchants, for example the etchant based on citric acid mentioned above and a second etchant based on Na2Cr2O7.