Pulsed electron beam annealing of GaAs after high dose implantation of hydrogen

Undoped (100) GaAs crystals were implanted with 0.5, 1.0 and 2.0 MeV protons at high fluences of about 5 x 10(17) ions cm(-2). After implantation the samples were subjected to pulse electron beam annealing (PEBA) at variable energy densities. The samples were analysed with alpha particle channeling as well as with electron channeling patterns (ECP), in order to evaluate the damage introduced during implantation. Surface and compositional studies were performed by means of scanning electron microscopy (SEM) and energy dispersive X-rays (EDX) respectively. Unimplanted samples exhibit a peculiar surface structure after pulsed electron beam annealing at energy densities above 0.9 J cm(-2), consisting of regular rectangles with variable side lengths in the range of 10 to 200 mu m. After high dose proton implantation the PEBA threshold energy density for observing these structures could be reduced to 0.4 J cm(-2). Cross sectional SEM samples reveal a cracked subsurface region at the position where these rectangular blocks separate from the bulk crystal. Deeper into the crystal the ion implanted damage distribution, which correlated well with TRIM calculations, was also observed.