Numerical investigation of digitised parabolic quantum wells for terahertz AlGaAs/GaAs structures

The calculations of quasi-parabolic quantum wells (QW) with smooth and digitised potential distributions on GaAs/Al_0.42Ga_0.58As system for 1 divide 7 THz frequencies are accomplished by numerical 1D Schrodinger equation solvers. It is shown that for energy eigenvalues equal spacing in smooth QWs the 18% quartic addition to parabolic potential is needed to compensate the electron effective mass increase in Al_xGa_{1 - x}As as x rarr 0.42. The optimisation of digitised multibarrier distributions revealed existence of two types of optimal solutions. At that the second type with periodically filled centre yielded low rms-deviations below 5% for energy spacings in frequency range 4 divide 7 THz. For frequencies below 2 THz the accuracy of digitised approach became insufficient to guarantee reasonably equally spaced energy levels