Long-distance transport of hot carriers due to acoustic phonon bottleneck in PbSe with room-temperature sensitive mid-infrared sensing

In the optoelectronic conversion process of semiconductors, the photo-excited carriers with energy higher than energy band edge, i.e., hot carriers, have always fast (picoseconds scale) dissipated within 100 nanometers distance through lattice scattering. Specifically, the hot carriers relaxation accounts for more than 60% energy loss in narrow bandgap semiconductor. Herein, we observe an ultralong transport of hot carriers (558 nm) by local light excitation in single-crystalline thermoelectric semiconductor PbSe via the time-resolved reflectivity dynamics. The ultraweak phonon emission of PbSe results in a long-distance thermalized carriers transport due to acoustic phonon bottleneck. Furthermore, the hot carriers effect gives rise to a self-driven (zero bias), fast (900 ns), and sensitive (D* = 1.1 × 1010 cm Hz1/2 W−1 at 3.3 μm) mid-infrared detection and imaging at room temperature. Our discovery provides an insight into optoelectronic conversion mechanism of narrow bandgap thermoelectric semiconductors with intriguing optoelectronic applications.