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.

Comparison of Be and C Diffusion in Heavily Doped Polycrystalline GaAs. K.Mochizuki, T.Nakamura: Applied Physics Letters, 1994, 65[16], 2066-8