Single crystal growth and transport properties of narrow-bandgap semiconductor RhP₂

We report the growth of high-quality single crystals of RhP 2 , and systematically study its structure and physical properties by transport, magnetism, and heat capacity measurements. Single-crystal x-ray diffraction reveals that RhP 2 adopts a monoclinic structure with the cell parameters a = 5.7347(10) Å, b = 5.7804(11) Å, and c = 5.8222(11) Å, space group P 2 1 / c (No. 14). The electrical resistivity ρ ( T ) measurements indicate that RhP 2 exhibits narrow-bandgap behavior with the activation energies of 223.1 meV and 27.4 meV for two distinct regions, respectively. The temperature-dependent Hall effect measurements show electron domain transport behavior with a low charge carrier concentration. We find that RhP 2 has a high mobility μ e ∼ 210 cm 2 ⋅V −1 ⋅s −1 with carrier concentrations n e ∼ 3.3 × 10 18 cm −3 at 300 K with a narrow-bandgap feature. The high mobility μ e reaches the maximum of approximately 340 cm 2 ⋅V −1 ⋅s −1 with carrier concentrations n e ∼ 2 × 10 18 cm −3 at 100 K. No magnetic phase transitions are observed from the susceptibility χ ( T ) and specific heat C p ( T ) measurements of RhP 2 . Our results not only provide effective potential as a material platform for studying exotic physical properties and electron band structures but also motivate further exploration of their potential photovoltaic and optoelectronic applications.