Abstract

The mirrors of a semiconductor laser are usually formed by manually scribing the crystal to induce a cleaved facet. This procedure is adequate for simple lasers where the cleaves do not have to be aligned with any feature on the surface or when the exact length of the laser is not critical. However, there are many devices where the cleave must be aligned with features on the top surface such as a waveguide, electrode, or other integrated optical or electrical component. In addition, the performance of some devices such as cleaved-coupled-cavity (C³) lasers depends critically on the cavity lengths. For these reasons, we have developed a technique for precise positioning of the laser mirror cleaves. This paper describes use of photoelectrochemical (PEC) etching¹ of deep narrow grooves into the laser substrate to weaken the crystal along specific lines and induce cleaves along these lines when the wafer is flexed. Our goal was wafer production of C³ lasers with a 40-μm long cavity coupled to a 210-μm long cavity. The two cavities of a C³ laser were held together with a 1-μm thick Au pad on the p side [Fig. 1(a)]. Groove-induced cleaves were used for the end facets as well as the internal facet. An SEM photo of a pair of grooves is shown in Fig. 1(b). Starting from a mask opening of 5μm, grooves 60 μm deep were routinely etched. Straight-walled flat-bottomed grooves [Fig. 1(c)] were etched when a stop-etch layer was used, such as p-type material or a wider band gap semiconductor that was transparent to the incident light.

© 1985 Optical Society of America