Raman characterization of structural disorder and residual strains in micromachined GaAs

Structural disorder and strain effects in ductile-regime single-point-diamond-turned gallium arsenide monocrystalline samples were probed by Raman scattering. The positive frequency shift of the longitudinal and transverse optical phonons observed in the machined samples indicate a residual compressive stress of about 1.5 GPa. This residual strain was attributed to the hysteresis of phase transformation generated by the high pressure imposed by the cutting tool tip during the machining process. The broadening of the Raman peaks indicate a high degree of structural disorder in the GaAs lattice. Moreover, the Raman spectrum of annealed samples, after machining, shows a less disordered but still misoriented matrix. In addition, it was found that crystalline arsenic formed into the surface vicinity.