Etch damage and deposition repair of vertical-cavity surface-emitting lasers

Dielectric layers are often employed as etch masks for mesa and trench structures during vertical-cavity surface-emitting laser (VCSEL) fabrication. The removal of these mask layers by reactive ion etching results in unavoidable exposure of the top laser facet to sputtering. This sputtering is experimentally shown to impact the device performance. After a thickness of less than a quarter wavelength (∼60 nm) has been removed, the VCSELs are no longer able to achieve lasing threshold. Simulation indicates that the reason for this is a decrease in quality factor by more than an order of magnitude. Consistent with this explanation is that the damage can be partially repaired (allowing laser oscillation) by depositing SiO2 to compensate for the missing semiconductor material.