Low-temperature CAIBE processes for InP-based optoelectronics

We have developed Cl₂/Ar and IBr₃/Ar chemically-assisted ion-beam etching (CAIBE) processes, which allow high-quality etching of InP-based materials such as laser mirrors and gratings at low substrate temperatures (≈0°C). Etch rates of 400-750 Å/min and excellent surface morphologies at substrate temperatures between -5°C and +10°C with both Cl₂/Ar and IBr₃/Ar process (400 V Ar ion beam) are achieved. These low temperatures have allowed us to utilize UV-baked photoresists as well as PMMA as etch masks, facilitating very simply process development. Higher substrate temperatures (+50°C to +120°C) yield still higher etch rates, but at the expense of severely degraded surface morphologies. An InGaAsP/InP (1.55 μm) bulk laser with one facet etched the other cleaved is demonstrated, and compared with a both facets cleaved laser