InGaAsP/InP 1.55-micron lasers with chemically assisted ion beam-etched facets
InGaAsP/InP 1.55-mikron Laserdioden mit trockengeätzten Facetten
Chemically assisted ion beam etching (CAIBE) involving an Ar ion beam an a halogen ambient gas (Cl2, IBr3) has been used to etch high-quality laser facets for InGaAsP/InP bulk lasers (1.55 micron). We achieved etch rates of 40.0 - 75.0 nm min(exp -1) at substrate temperatures between -5 and +10 deg C. These low temperatures have allowed us to utilize UV-baked photoresists as well as PMMA as etch masks, facilitating very simple process development. Higher substrate temperatures (50 to 120 deg C) yield still higher etch rates, but at the expense of severely degraded surface morphologies. Angle resolved x-ray photoelectron spectroscopy (XPS) was investigated for observing etched InP surfaces. A disproportioned surface has been detected after etching in the higher temperature range; low temperatures yield stoichiometric surfaces.