Nonuniform reactive ion etching of MnAs/GaAs heterostructures:: MnAs nanodots and GaAs nanocolumns

Under certain conditions, the reactive ion etching of MnAs layers grown on GaAs substrates proceeds in a remarkably nonuniform manner. Mounds are formed on the surface of the MnAs layers during the etching. They eventually result in submicron-scale islands when the etch front reaches the MnAs/GaAs interface. Because of the one-order-of-magnitude smaller etch rate for MnAs than that for GaAs, GaAs columns having large height-to-width ratios are subsequently generated when the etching further progresses. The nonuniform etching takes place when the MnAs surface is partly covered with a resist, indicating the inhomogeneous migration of etching species is crucial.