Determining the Intrinsic and Extrinsic Properties of Black Phosphorus by AC Conductance and Capacitance Techniques

Most studies on the electrical properties of the black phosphorus (BP) are based on direct-current (DC) measurements. We study BP capacitors by probing the intrinsic and extrinsic material properties of BP by capacitance and AC conductance measurements. We determine the transport band gap of 50 nm BP as 0.31 eV based on the temperature dependence of the transition frequencies. By modeling, doping concentration of the BP as 3 x 10¹⁸ in a BP/BN capacitor and as 1.8 x 10¹⁸ in a BP/Al₂O₃ capacitor are extracted, suggesting Al₂O₃ deposited by atomic layer deposition (ALD) introduces n-type doping (counter-doping) to the originally p-type doped BP crystals. The interface states in BP/Al₂O₃ capacitors from AC conductance method exhibits a U-shaped energy distribution with the minimum located at the midgap. The interface trap density in the BP/BN capacitor is around one order lower than that in the BP/Al₂O₃ capacitor. We also propose to fabricate BP MOSFET and extracted barrier heights hence bandgap by I_d-V_g characteristics and make a comparison to E_g above. This investigation of properties of BP will provide important information for designing and fabricating future electronic/photonic devices based on this material.