New experimental evidence of surface ripples on gallium arsenide in laser annealing

This letter presents new experimental evidence of periodic structure or ripples which occur on the surface of crystalline or ion-implanted gallium arsenide in laser annealing. A new kind of ripple, whose direction does not depend on the electric field vector of the laser beam, appears for the larger angle of incidence between the laser beam direction and the surface normal. The variation in this ripple spacing with the incident angle of the laser beam to the surface normal is different from that for previously reported ripples, whose direction is always found to be almost perpendicular to the electric field vector for the linearly polarized laser beam. We suggest that the spacing for the new ripples can be interpreted from the reinforcement of the initially induced weak and straggling surface disturbances caused by the interference between the incident laser beam and succesively scattered waves.