Determination of the density of states in quantum wells and quantum dot arrays by the capacitance-voltage method

The possibility of determining the electronic density of states in quantum wells and quantum dot arrays in heterostructures from the capacitance-voltage curve is investigated. In heterostructures fluctuations of the composition and geometrical dimensions play an important role. It is shown that to reconstruct the exact density of states from the measured capacitance-voltage curve is impossible, because this problem is ill-posed from the mathematical point of view. An approximate method is proposed for solving the problem, involving the determination of a “reduced” density of states. It is shown that the reduced density of states is close to the true density if the characteristic energy scale governing the variation of the latter is much greater than the thermal energy kT. The proposed method is used to find the density of states in the conduction band of a quantum well in an In_0.22Ga_0.78As/GaAs heterostructure. Fiz. Tekh. Poluprovodn. 33, 1246–1252 (October 1999)