Samples of n-type and p-type δ-doped material, grown by molecular beam epitaxy and with quite high doses of Si, were investigated by means of transmission electron microscopy. The magnitude of the doses ranged from half a monolayer to 2 monolayers. The microscopic structures of the δ-doped regions and of the adjacent epilayers were observed directly. The effect of impurity spreading upon the hetero-interfaces and superlattices was studied, and it was found that the Si atoms in Si δ-doped samples were confined to within a few atomic layers. Stacking faults were found in δ-doped samples when they were grown at low temperatures. Their presence was attributed to local strains that were caused by heavy doping.

D.G.Liu, J.C.Fan, C.P.Lee, K.H.Chang, D.C.Liou: Journal of Applied Physics, 1993, 73[2], 608-14