Electrical Profiles of Silicon Implanted Gallium Arsenide

The purpose of the present work was to investigate the carrier concentration and mobility profiles of Silicon (S1)-doped Gallium Arsenide (GaAs) samples. Silicon atoms were doped at room temperature, at an energy of 120 keV and with two different doses, 1 x 1013 and 3 x 1013 cm-2, into epitaxial GaAs substrate. Silicon nitride (Si3N4) films were deposited on the samples by a Plasma-Enhanced-Deposition technique to protect the samples from out-diffusion and dissociation during high temperature anneal. The samples were then annealed at three different temperatures, 850, 900 and 950oC for 15 minutes. The electrical characterization of these samples was done by using the van der Pauw Hall effect/Sheet resistivity technique to repeatedly measure the samples after consecutive acid etches. Differential calculations were carried out for each layer. The total etched depth was measured using an interference technique. Carrier concentration and mobility profiles were plotted for all samples at three different anneal temperatures. In almost all cases, the carrier concentration profiles are roughly gaussian in shape, but the projected ranges are displaced from the theoretical LSS value. For 1 x 1013 cm-3 dose samples, and 850oC anneal gives optimum activation, while 3 x 1013 cm-2 dose samples give best activation at 900oC. The mobility profiles are found to be roughly constant, around 3000 cm2 /V-sec