Abstract

The idea about a new type of THz modulator, based on the dependence of separation between space quantized energy levels in a quantum well (QW) on the degree of ionization of shallow impurity delta doped layer situated within the QW is supported with theoretical calculations of absorption coefficients for intersubband optical transitions of n-type Si0.8Ge0.2/Si/Si0.8Ge0.2 QW structure. Both center and edge doping of two QWs widths of - 10 and 20 nm - were considered at lattice temperatures 4 and 77 K for low and high degrees of impurity ionization. The obtained results are explained and they point to out the ranges of THz tuning of the structures under study. It is also emphasized that besides the electric field the changing temperature can control the efficiency of THz modulation. (C) 2015 Elsevier Ltd. All rights reserved.