Samples of n-type and p-type δ-doped material, grown by molecular beam epitaxy and with quite high doses of Be, 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. The Be atoms which were present in Be δ-doped samples spread over a wide region and caused rough hetero-interfaces and wavy superlattices to form. The spreading of Be was attributed to segregation and diffusion which occurred during growth. 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