Theoretical and experimental studies in n-type modulation-doped InxGa1-xAs/InyAl1-yAs/InP magnetic sensors

We present a theoretical study of the quantized electronic states in both n -type uniformly doped and delta-doped double quantum well (DQW) InxGa1-xAs/ InyAl1-yAs heterostructures. The shape of the confining potential, the subb and energies and their occupancies, the eigen envelope wave functions, and the Fermi energy in the quantum wells were calculated self-consistently tak ing into account exchange-correlation and strain effects. The influence of the doping contents, the thicknesses of the barrier, and the channel sheet layers on the confinement properties of these heterostructures will be disc ussed. By optimizing the parameters of the InxGa1-xAs/InyAl1-yAs heterostru ctures to be used as Hall magnetic sensors, we have demonstrated that the p arallel conduction in the InyAl1-yAs barrier can be suppressed and the dens ity of the two-dimensional electron gas in the InxGa1-xAs channel is reduce d as well. Hall data, obtained on molecular beam epitaxy grown Si modulatio n-doped InxGa1-xAs(x = 0.75)/InyAl1-yAs DQWs, are used as an experimental s upport to validate our calculation. A deep lying defect has been detected t hrough the observation of persistent photoconductivity (PPC) at low tempera ture. We have also studied the effects of this PPC on the transport propert ies of the heterostructures investigated. A detailed analysis of all these results will be presented. (C) 1999 American Institute of Physics. [S0021-8 979(99)04214-0].