Characterization of damage in InP dry etched using nitrogen containing chemistries

Abstract

Etching of InP by different ion beam etching processes using chemistries containing nitrogen, such as nitrogen milling, N(CH3)3 and Ar/N(CH3)3 based reactive ion beam etching (RIBE), and N2/CH4/H2 based chemically assisted ion beam etching (CAIBE), is investigated. The residual surface damage is characterized using I–V characteristics of Au/InP metal–semiconductor (MS) contacts and photoluminescence (PL) yield measurements from near surface quantum wells and bulk InP. The contacts formed on as-etched surfaces, irrespective of the etch process, show ohmic behavior. On the other hand, although the PL yield is reduced for the different processes, the measured intensities show variations which are attributed to passivation of defects by hydrogen. Secondary ion mass spectroscopy (SIMS) was used to check (qualitatively) the presence of nitrogen in the etched and annealed InP samples. SIMS data show the presence of nitrogen in the near surface region of the etched samples, but nitrogen levels drop to background levels upon annealing at typical regrowth conditions (650 °C under phosphine flow). Interestingly, the annealing step results not only in a significant recovery of the PL yield, but also in a recovery of Schottky characteristics of the Au contacts formed on the annealed surfaces. These observations show that the etch-induced damage is significantly reduced by annealing and suggests recovery of the near-surface stoichiometry and possibly reduction of nitrogen-related defects.