The effects of background doping, surface encapsulation, and an As4 over-pressure upon C diffusion were studied by annealing samples which had 100nm p-type C doping spikes within 0.00lmm layers of undoped (n-), Se-doped (n+) and Mg-doped (p+) material. The layers were grown via low-pressure metalorganic chemical vapor deposition, using CCl4 as the dopant source. Two different As4 over-pressure conditions were investigated. These were those of an equilibrium PAs (no excess As), and of a pressure, PAs, of about 2.5atm. For each As4 over-pressure condition, both capless and Si3N4-capped samples of the n-, n+ and p+ crystals were simultaneously annealed (825C, 24h). Secondary-ion mass spectroscopy was used to measure atomic C depth profiles. The C diffusion coefficient was always low, but depended upon the background doping. It was highest in Mg-doped (p+) material and was lowest in Se-doped (n+) material. The effect of Si3N4 surface encapsulation and PAs upon C diffusion was minimal.

B.T.Cunningham, L.J.Guido, J.E.Baker, J.S.Major, N.Holonyak, G.E.Stillman: Applied Physics Letters, 1989, 55[7], 687-9