Selenium vacancies induced surface oxygen adsorption and sensitization mechanism of PbSe film: Experimental and computational

Lead selenide (PbSe) is widely considered to be an ideal material for room temperature mid-wave infrared (MWIR) detection. The MWIR response of PbSe leaps obviously after sensitization in a particular oxidizing process. However, the mechanism of such characteristics has not been specifically understood. Here, the oxygen (O) sensitization reaction process is affirmed by experiment and computation. In the process of film preparation, Se atoms fractionate from the (200) plane of PbSe lattice and leave Se vacancies (VSe). Then, O-2 molecules adsorbed at VSe and subsequently disintegrate into O atoms occupying VSe. The O indrawing forms new energy levels and reduces the band gap (Eg), realizes the conductivity transformation from n-to p-type, decreases carrier concentration, and enhances carrier mobility. The variation of conductivity inhibits the dark current of PbSe detectors and increases the mobility of photon-generated carriers at the same time, resulting in the improvement of the IR detection performance.