Bandgap and exciton binding energies of hexagonal boron nitride probed by photocurrent excitation spectroscopy

• Published in: Applied physics letters 2016-09, Vol.109 (12)
• Main Authors: Doan, T. C., Li, J., Lin, J. Y., Jiang, H. X.
• Format: Article
• Language: English
• Subjects: Applied physics; Binding energy; Boron nitride; Chemical synthesis; Excitation spectra; Excitons; Impurities; Metalorganic chemical vapor deposition; Organic chemicals; Organic chemistry; Parameters; Photoelectric effect; Photoelectric emission; Photoluminescence; Spectroscopy; Spectrum analysis; Ultrawideband; Wide bandgap semiconductors
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4963128

Photocurrent excitation spectroscopy has been employed to probe the band structure and basic parameters of hexagonal boron nitride (h-BN) epilayers synthesized by metal-organic chemical vapor deposition. Bias dependent photocurrent excitation spectra clearly resolved the band-to-band, free exciton, and impurity bound exciton transitions. The energy bandgap (Eg), binding energy of free exciton (Ex), and binding energy of impurity bound exciton (Ebx) in h-BN have been directly obtained from the photocurrent spectral peak positions and comparison with the related photoluminescence emission peaks. The direct observation of the band-to-band transition suggests that h-BN is a semiconductor with a direct energy bandgap of Eg = 6.42 eV at room temperature. These results provide a more coherent picture regarding the fundamental parameters of this important emerging ultra-wide bandgap semiconductor.