Tuning the charge states in InAs/GaSb and InAs/GaInSb composite quantum wells by persistent photoconductivity*

Inverted InAs/GaSb quantum wells (QWs) and InAs/GaInSb QWs have been proved to support the quantum spin Hall states. In this talk, we will show how to use the persistent photoconductivity (PPC) to tune the bulk band structure and carrier densities in inverted InAs/GaSb QWs and InAs/GaInSb QWs. Experimentally, we used light-emitting diodes (LEDs) with different light-emitting wavelengths to illuminate the samples at low temperature. We found the persistent photoconductivity in these system could be negative or positive, depending on the specific doping structure and the illuminating photon energy. Compared to the widely-used electrostatically gating method, our findings provide a more flexible and non-invasive way to control the band structures and charge states in InAs/GaSb QWs and InAs/GaInSb QWs.