Probing room temperature indirect and minimum direct band gaps of h-BN

Journal Article · 01 September 2024 · Applied Physics Express

DOI: https://doi.org/10.35848/1882-0786/ad777a · OSTI ID:2580345

Hossain, N.; Tingsuwatit, A.; Alemoush, Z.; Almohammad, M.; Li, J.; Lin, J. ; Jiang, H.

Abstract Hexagonal boron nitride (h-BN) has attracted considerable interest as an ultrawide bandgap (UWBG) semiconductor. Experimental studies focused on the detailed near band-edge structure of h-BN at room temperature are still lacking. We report a direct experimental measurement of the near band-edge structure performed on h-BN quasi-bulk wafers via photocurrent excitation spectroscopy (PES). PES resolved the band-to-band transitions near M- and K-points in the Brillion zone (BZ), from which the room temperature indirect band gap of $E_g^{MK}$ ∼6.02 eV, minimum direct bandgap at M-point of $E_g^M=6.36\mathrm{eV}$ and next lowest direct energy bandgap at K-point of $E_g^K=6.56\mathrm{eV},$ have been simultaneously determined for the first time experimentally. The measured energy differences between K- and M-points in the conduction band minimum (CBM) and valence band maximum (VBM) are Δ $E_C^{MK}=0.54\mathrm{eV}$ and Δ $E_V^{MK}$ = 0.34 eV, respectively, in good agreement with the calculation results. Significantly differing from its III-nitride wurtzite counterparts, in which only electrons and holes in the conduction and valence band extremes at the Γ-point are predominantly involved in the optical and transport processes, the results highlighted that charge carriers associated with both M- and K-valleys control to the optical excitation, recombination and charge transport processes in h-BN.

• Research Organization: Texas Tech Univ., Lubbock, TX (United States)
• Sponsoring Organization: USDOE Advanced Research Projects Agency - Energy (ARPA-E)
• Grant/Contract Number: AR0001785; AR0001552
• OSTI ID: 2580345
• Journal Information: Applied Physics Express, Journal Name: Applied Physics Express Journal Issue: 9 Vol. 17; ISSN 1882-0778
• Publisher: Japan Society of Applied PhysicsCopyright Statement
• Country of Publication: United States
• Language: English