Precise nonselective chemically assisted ion-beam etching of AlGaAs/GaAs Bragg reflectors byin situ laser reflectometry

Precision etch-depth control is realized by a chemically assisted ion-beam etching system incorporated within situ laser reflectometry. By counting the number of interference fringes, etch-depth control better than a quarter-wave thickness is easily obtained. Optimized etching conditions for highly anisotropic etching of bulk GaAs and AlGaAs/GaAs distributed Bragg reflectors are obtained. With the ability to etch-stop just below the active region by thein situ monitoring, InGaAs vertical-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 over 20 pairs of quarter-wave stacks of AlGaAs/GaAs distributed Bragg reflectors.