PLASMA AND WET CHEMICAL ETCHING OF IN0.5GA0.5P

Dry and wet chemical etching of epitaxial In0.5Ga0.5P layers grown on GaAs substrates by gas-source molecular beam epitaxy have been investigated. For chlorine-based dry etch mixtures (PCl3/Ar or CCl2F2/Ar) the etching rate of InGaP increases linearly with dc self-bias on the sample, whereas CH4/H2-based mixtures produce slower etch rates. Selectivities of greater-than-or-equal-to 500 for etching GaAs over InGaP are obtained under low bias conditions with PCl3/Ar, but the surface morphologies of InGaP are rough. Both CCl2F2/Ar and CH4/H2/Ar mixtures produce smooth surface morphologies and good (> 10) selectivities for etching GaAs over InGaP. The wet chemical etching rates of InGaP in H3PO4:HCl:H2O mixtures has been systemically measured as a function of etch formulation and are most rapid (approximately 1-mu-m.min-1) for high HCl compositions. The etch rate, R, in a 1:1:1 mixture is thermally activated of the form R is-proportional-to e(-Ea/kT), where E(a) = 11.25 kCal.mole-1. This is consistent with the etching being reaction-limited at the surface. This etch mixture is selective for InGaP over GaAs.