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

Abstract <p>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 <math> <msubsup> <mrow> <mi>E</mi> </mrow> <mrow> <mi>g</mi> </mrow> <mrow> <mi>M</mi> <mi>K</mi> </mrow> </msubsup> </math> ∼6.02 eV, minimum direct bandgap at M-point of <math> <msubsup> <mrow> <mi>E</mi> </mrow> <mrow> <mi>g</mi> </mrow> <mrow> <mi>M</mi> </mrow> </msubsup> <mo>=</mo><mn>6.36</mn><mspace /><mi mathvariant="normal">eV</mi> </math> and next lowest direct energy bandgap at K-point of <math> <msubsup> <mrow> <mi>E</mi> </mrow> <mrow> <mi>g</mi> </mrow> <mrow> <mi>K</mi> </mrow> </msubsup> <mo>=</mo><mn>6.56</mn><mspace /><mi mathvariant="normal">eV</mi><mo>,</mo> </math> 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 <math> <msubsup> <mrow> <mi>E</mi> </mrow> <mrow> <mi>C</mi> </mrow> <mrow> <mi>M</mi> <mi>K</mi> </mrow> </msubsup> <mo>=</mo><mn>0.54</mn><mspace /><mi mathvariant="normal">eV</mi> </math> and Δ <math> <msubsup> <mrow> <mi>E</mi> </mrow> <mrow> <mi>V</mi> </mrow> <mrow> <mi>M</mi> <mi>K</mi> </mrow> </msubsup> </math> = 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 . Authors: Hossain, N.; Tingsuwatit, A.; Alemoush, Z.; Almohammad, M.; Li, J.. DOE Contract: AR0001552; AR0001785. Subjects: Physics