Reactive ion etching induced damage in GaAs and AlGaAs using C2H6/H2/Ar or CCl2F2/O2 gas mixtures

Changes in the near-surface electrical properties of n-type (n=1×1017 cm−3) GaAs and AlGaAs after reactive ion etching in C2H6/H2/Ar or CCl2F2/O2 discharges (4 mTorr, 0.85 W cm−2) were investigated by current-voltage (I-V) and capacitance-voltage measurements on Schottky diodes. Carrier reductions of approximately an order of magnitude were observed immediately after etching GaAs and AlGaAs in ethane-hydrogen-argon; much smaller changes (∼20%) were observed using freon-12–oxygen. For both gas chemistries, annealing in the range 200–300 °C produced the most ideal I-V characteristics in GaAs, whereas 300–400 °C was required for AlGaAs. Replacing H2 by D2 allowed high sensitivity atomic profiling using secondary ion mass spectrometry. Permeation of D2 to depths of ∼0.5 μm is observed in both GaAs and AlGaAs after etching—the D2 diffuses rapidly around 400 °C where dopant reactivation occurs.