Under growth conditions which were optimized so as to give the best transport with normal-side doping, the migration of the Si dopant towards the inverted interface during growth was the main reason for a reduced inverted well mobility. This discovery permitted the preparation of modulation-doped inverted quantum wells of unprecedented quality.

L.Pfeiffer, E.F.Schubert, K.W.West, C.W.Magee: Applied Physics Letters, 1991, 58[20], 2258-60