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

Abstract
Changes in the near‐surface electrical properties of n‐type (n=1×1017 cm3) GaAs and AlGaAs after reactive ion etching in C2H6/H2/Ar or CCl2F2/O2 discharges (4 mTorr, 0.85 W cm2) were investigated by current‐voltage (IV) 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 IV 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.