High-Temperature In situ Deformation of GaAs Micro-pillars: Lithography Versus FIB Machining

The plasticity of silicon-doped GaAs was investigated between 25 degrees C and 400 degrees C using microcompression to prevent premature failure by cracking. Micropillars with diameters of similar to 2.5 mu m were fabricated on a < 100 >-oriented GaAs single crystal by means of both conventional lithographic etching techniques and focused ion beam machining and then compressed in situ in the scanning electron microscope (SEM). A transition in deformation mechanisms from partial dislocations to perfect dislocations was found at around 100 degrees C. At lower temperatures, the residual surface layer from lithographic processing was found to provide sufficient constraint to prevent crack opening, which resulted in a significant increase in ductility over FIB-machined pillars. Measured apparent activation energies were found to be significantly lower than previous bulk measurements, which is mostly attributed to the silicon dopant and to a lesser extent to the size effect.