Intersubband linear and nonlinear optical response of the delta-doped SiGe quantum well

• We calculate linear and non-linear intersubband optic properties of QWs.
• Energy structure of delta-doped inside well QWs was calculated self-consistently.
• We allowed for the impurity binding energy change.
• Edge-doped well gives an additional peak in absorption with small nonlinearity.
• The effects studied can be used to engineer tunable THz optical devices.

The degree of ionization, controlled by external fields, of delta-doped layers inside the quantum wells can affect their energy structure, therefore delta-doped QWs can be used to engineer different kinds of tunable THz optical devices on intersubband transitions. Here it is calculated and analyzed the linear and nonlinear (Kerr-type) optical response, including absorption coefficient and refractive index change of 20 nm-wide Si0.8Ge0.2/Si/Si0.8Ge0.2 QW structures n-delta-doped either at the center or at the edge of the well under different temperatures. The conduction subband energy structure was found self-consistently, including the calculation of the impurity binding energy. Our results show that the degree of ionization of the impurity layer as well as the heterostructure symmetry has a strong influence on optical properties of the structures in THz region.