High-performance uncooled mid-infrared lead salt photodetectors: Revealing surface passivation and charge transport mechanisms

Abstract

Uncooled mid-infrared lead-salt photodetectors are considered promising candidates for next-generation infrared optoelectronic devices that meet the small size, low weight, high performance, low power consumption, and low price (SWaP3) standards. However, research on the internal charge transport mechanisms of these devices is currently very limited, resulting in a lack of deep understanding of the key transport mechanisms, which seriously hinders the development of uncooled mid-infrared photodetectors. Here, high-performance uncooled PbSe photodetectors with different iodine contents were fabricated, achieving a high specific detectivity of 1.68 × 1010 Jones at 300 K. Through the temperature dependence of the conductivity, the charge transport mechanisms at different temperatures were revealed, showing that at low temperatures, charge transport follows the variable-range hopping mechanism, whereas near room temperature, grain boundary barrier transport dominates, with a transition temperature of Tc = 217.4 K. A grain boundary transport model for charge carriers was proposed, revealing the regulatory effect of iodination on the device's grain boundary barriers. The study also investigated the space charge effects within the devices, diffusion currents, and electron tunneling characteristics, uncovering for the first time the space charge-limited transport mechanism and the Poole–Frenkel effect under high bias conditions. The findings provide new insights into device physics for high-performance uncooled lead-salt photodetectors.