Mobility modulation effects in a double quantum well infrared   photon-detector
  An electrically isolated quantum well (QW) island can be positively charged by incoming infrared photon, because its electrons absorb photon energy via intersubband transition and acquire enough energy to escape it. This process has been used in a double QW photon-detector. Here, we present the observation of so-called negative photon-response in such detector. Its origin is clarified to be an electron mobility reduction phenomenon resulted from the photon induced charges. 
Ting-Ting Kang, Susumu Komiyama, Takeji Ueda, Shi-Wei Lin, and   Sheng-Di Lin
cond-mat.mes-hall