Magnetic depopulation of electronic subbands in low-dimensional semiconductor systems and their influence on the electrical resistivity and Hall effect

In many modern semiconductor devices transport is no longer three-dimensional because electrical confinement may split up the density of states such that several two-dimensional (2D) or one-dimensional ( 1 D) sub-bands are occupied. A suitably orientated magnetic field causes depopulation ( emptying) of higher subbands. This occurs because the magnetic field has two effects; firstly it diamagnetically increases the energy levels and separations and secondly, it increases the density of states. Calculations of these effects have been made using the WKB method for MESFET/JFET type devices ( depopulation of 2D sub-bands) and for a model potential of a confined 2DEG ( depopulation of 1 D sub-bands). We outline the behaviour of the electrical resistance under such conditions and comment on the effect of such depopulation on the Hall effect ( including the quantum Hall effect) as 1 D sub-bands are depopulated.