Detection of DX-like trapping centres in delta-doped pseudomorphic InxGa1-xAs quantum wells

A set of 60 Angstrom wide Al0.33Ga0.67As/InxGa1-xAs/Al0.33Ga0.67As quantum wells (0 < x < 20%), delta-doped in the centre with Si at 6.8 x 10(12) cm(- 2), was grown pseudomorphically on GaAs substrates by molecular beam epitax y and characterised by Hall effect measurements. A decreasing free carrier concentration was seen with increasing In content in the quantum well. Self -consistent solution of the coupled Poisson and Schrodinger equations for t hese structures showed that this behaviour corresponded to a gradual reduct ion in Fermi energy, which we attribute to Fermi-level pinning by DX-like c entres whose formation energy decreases with increasing In content. Theoret ical modelling shows that it is necessary to consider the effects of the bi axial compressive strain in the InxGa1-xAs to account for this shift in DX centre position. (C) 1998 Elsevier Science Ltd. All rights reserved.