Effect of Air Atmosphere Sensitization on Formation of PbSe p–n Junctions for High-Performance Photodetectors

Abstract

Photodetectors based on polycrystalline lead salts are widely used to detect light in the mid-infrared range because they can be used at room temperature. In their fabrication, the sensitization process is considered to be the most critical factor. In this work, the crystalline structure of PbSe films deposited by electron-beam evaporation was analyzed by scanning electron microscopy, x-ray diffraction, and x-ray photoemission spectroscopy. The results showed that lead oxides were formed during the annealing process. We also investigated the electrical properties of the samples by Hall-effect measurements. In photodetection experiments at room temperature, the PbSe-based photodetectors showed responsivity and detectivity of 0.16 A/W and 6.66 × 10⁸ cm Hz^1/2/W, respectively. Remarkably, we measured a photocurrent even without applying a bias voltage, which implies that the p–n junctions separate the carriers in these films, thus also proving the existence of micro p–n junctions in the film. A carrier separation model is proposed to describe the conduction process.