The bandgap of black phosphorus is widely tunable, depending on the number of layers, external electric field, and strain. Since the bandgap of black phosphorus is very narrow, it is difficult to measure using standard photoluminescence and absorption spectroscopy in the visible range. In this paper, we propose a method to extract the bandgap of black phosphorus using capacitance measured at various temperatures and frequencies. From the transition frequency or transition temperature, where C-V changes from high-frequency to low-frequency behavior, we can extract the bandgap information. Using this method, we extracted the bandgap of black phosphorus with a thickness of 50 nm to be 0.30 eV. For comparison, we also extracted the bandgap of black phosphorus using minimum conductance and threshold voltage methods, and the results are consistent with those of the C-V method. This C-V method can overcome the wavelength limitation of the photoluminescence measurement and spatial resolution limitation of Fourier transform infrared spectroscopy. Another advantage of this C-V method is that the extracted bandgap is unaffected by the contact resistance and device area, making it reliable and convenient in determining the bandgap of narrow bandgap materials.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)