p-Type doping of II-VI heterostructures from surface states: application   to ferromagnetic Cd$_{1-x}$Mn$_x$Te quantum wells
  We present a study of p-type doping of CdTe and Cd$_{1-x}$Mn$_x$Te quantum wells from surface states. We show that this method is as efficient as usual modulation doping with nitrogen acceptors, and leads to hole densities exceeding $2 \times 10^{11}$ cm$^{-2}$. Surface doping was successfully applied to obtain carrier-induced ferromagnetism in a Cd$_{1-x}$Mn$_x$Te quantum well. The observed temperature dependence of photoluminescence spectra, and the critical temperature, correspond well to those previously reported for ferromagnetic quantum wells doped with nitrogen. 
W. Maslana, M. Bertolini, H. Boukari, P. Kossacki, D. Ferrand, J.A.   Gaj, S. Tatarenko, J. Cibert