Lowhyphen;temperature carrier distributions in wide quantum wells of different shapes from capacitancehyphen;voltage measurements

摘要

The carrier distributions in modulationhyphen;doped wide graded quantum wells that a measurement of the capacitanceCbetween a surface gate and an ohmic contact to the carriers as a function of the applied biasVwould yield are calculated. These capacitancehyphen;voltage (Chyphen;V) distributions are found to agree inexactly, but closely, with the calculated true carrier distributions. Density modulation features, induced by superlattices or by abrupt changes in the curvature of bandhyphen;gap grading, are strikingly reproduced. Electron distributions extracted from actual measurements on a wide parabolic well and on a parabolic well with superimposed superlattice are in good agreement with theory. For the case of the parabolic well, the occupancy of a finite number of subbands is manifested as structure in theChyphen;Vdistributions. This technique is relevant to the measurement of carrier distributions in any wide carrier system with more than one electric subband occupied.