Etch rates and surface chemistry of GaAs and AlGaAs reactively ion etched in C2H6/H2

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Abstract
The etch rates of GaAs and AlxGa1−xAs (x=0.09–1) in C2H6/H2 were investigated as a function of time (1–12 min), gas flow rate (5–25 sccm), total pressure (4–30 mTorr), plasma power density (0.56–1.32 W cm−2), and percentage of C2H6 in the discharge (10%–50%). The etch rates are constant with time, and decrease with increasing Al content in the AlGaAs. The maximum etch rates occur at 25% by volume C2H6 in H2 and increase linearly with increasing power density. Increasing the total pressure at constant gas composition reduces the etch rates by approximately a factor of 2 between 4 and 30 mTorr. The etched surfaces have smooth morphologies for C2H6 concentrations less than ∼40% of the total gas volume. A layer of subsurface dislocations approximately 40 Å deep were observed in GaAs by transmission electron microscopy for the highest‐power density discharges, while the surfaces for all samples are As‐deficient to a depth of ∼30 Å after reactive ion etching. Polymer deposition is not significant for C2H6 volumes less than 40% of the total gas volume.