Heavily-doped polycrystalline material which had been grown by molecular beam epitaxy and metalorganic chemical vapor deposition was studied by using secondary ion mass spectrometry and Hall measurements. It was found that Be rapidly diffused into the undoped buffer layer at a growth temperature of 450C. The concentration-depth profiles of Be in AlGaAs/GaAs heterojunction bipolar transistor layers indicated that Be diffused mainly along grain boundaries. On the other hand, C diffusion was negligible; even during post-growth annealing at 800C. However, annealing increased the resistivity of C-doped GaAs, and this was suggested to be due to a change in the occupation site preference of C atoms from As sites.

K.Mochizuki, T.Nakamura: Applied Physics Letters, 1994, 65[16], 2066-8