Terahertz photoconductivity in InAs/GaSb based quantum well system

Great attention has been paid to the terahertz (THz) technology due to its potential applications, in which THz radiation source and detector with excellent performances at the room temperature are most desired. The semi-classical Boltzmann equation is employed to study the response of electrons and holes to the electromagnetic radiation field in InAs/GaSb based type Ⅱ quantum well system (QWS). The balance equation method is used to solve the Boltzmann equation, and the influences of the structure of the QWS on the photoconductivity is studied in detail to reveal the mechanism of the photoconductivity in the QWS. The photoconductivity is influenced by the carrier density, the subband energy of the carriers and the coupling of the wavefunctions which can be modulated conveniently by the structure of the QWS. In this study, our attention focuses on the influence of the structure of the QWS on the conductivity. When the width of the InAs layer and the GaSb layer are both 8 nm, a sharp peak in photoconductivity is observed at about 0.2 THz due to the electron transition in different layers. The strength of the peak decreases slightly with the increase of the temperature, and a red shift is observed. However, the photoconductivity is not sensitive to the temperature and has good performances at relatively high temperatures up to the room temperature, which indicates that the InAs/GaSb based type-Ⅱ QWS can be used as a THz photoelectric device at room temperature.