Process damage in chemically assisted ion beam etching of InP/GaInAsP

We have investigated N₂/H₂/CH₄ based chemically assisted ion beam etching (CAIBE) of InP/GaInAsP using an inductively coupled RF plasma source and the ion energy was varied from 500 eV down to 75 eV. The etch rates, surface morphology and etch-induced damage have been studied. To distinguish the chemical role of H₂ and CH₄ in the etch process, nitrogen ion milling and N₂/CH₄ CAIBE processes were characterised. Photoluminescence yield was used to characterise the surface damage by using near surface quantum wells as probes and the etched surface morphology was quantified by roughness measurements by atomic force microscopy. Our results show that the 75 eV N₂/H ₂/CH₄ CAIBE process results in extremely smooth surfaces (rms. roughness <1 nm) and low optical damage. Further, the post-anneal photoluminescence intensities are seen to be correlated to the as etched surface morphologies: Intensity enhancement for samples with smooth surfaces and reduction for samples with rough surfaces