Linear and elliptical photogalvanic effects in two-dimensional Be₂Al photodetector

The photogalvanic effect (PGE) enables the generation of photocurrent at zero bias and without the need of building p–n junction, showing potential applications in the low-power two-dimensional optoelectronics. However, the PGE photocurrent is generally small and high photocurrents are needed which can be used as the photodetector in practice. Therefore in this paper, we built two photodetectors, namely armchair and zigzag photodetectors, based on the Be₂Al monolayer with its stabilization has been proved, and further studied linear and elliptical PGEs in these devices. It was found that when introducing the vacancy-doping and substitution-doping corresponding to the increasing of asymmetry from D_6H to D_2H or C_2V for the Be₂Al monolayer, the strength of PGE photocurrents have been considerably enlarged, showing robust PGEs generated in the armchair and zigzag Be₂Al photodetectors. Moreover, the photocurrents mainly show the relations cos(2θ) for the armchair photodetector and sin(2θ + θ₀) for the zigzag photodetector with their largest strength reaching up to 34.8 and 4.2 \(a_0^2\) $a_0^2$ /photon, respectively. In addition, results revealed that the linear PGEs were stronger than the elliptical PGEs, and for the circularly polarized light the strength of photocurrents did not change anymore exhibiting the existence of isotropic PGEs. Finally, high extinction ratios exhibited that the armchair and zigzag Be₂Al photodetectors were all polarization-sensitive. In conclude, these results manifested great potential applications of the Be₂Al photodetectors on high-performance optoelectronics and nanoelectronic devices.