PRECISE NONSELECTIVE CHEMICALLY ASSISTED ION-BEAM ETCHING OF ALGAAS GAAS BRAGG REFLECTORS BY IN-SITU LASER REFLECTOMETRY

Precision etch-depth control is realized by a chemically assisted ion- beam etching system incorporated with in situ laser reflectometry. By counting the number of interference fringes, etch-depth control better than a quarter-wave thickness is easily obtained. Optimized etching c onditions for highly anisotropic etching of bulk GaAs and AlGaAs/GaAs distributed Bragg reflectors are obtained. With the ability to etch-st op just below the active region by the in situ monitoring, InGaAs vert ical-cavity surface-emitting lasers with CW threshold current density as low as 380 A cm-2 with output power > 11 mW are fabricated. Spatial uniformity is 5% over a 1-cm2 sample, which corresponds to one pair o ver 20 pairs of quarter-wave stacks of AlGaAs/GaAs distributed Bragg r eflectors.