Band alignment of HfO2/AlN heterojunction investigated by X-ray photoelectron spectroscopy

Abstract

The band alignment between AlN and Atomic-Layer-Deposited (ALD) HfO 2 was determined by X-ray photoelectron spectroscopy (XPS). The shift of Al 2p core-levels to lower binding energies with the decrease of take-off angles h indicated upward band bending occurred at the AlN surface. Based on the angle-resolved XPS measurements combined with numerical calculations, valence band discontinuity DE V of 0.4 6 0.2 eV at HfO 2 /AlN interface was determined by taking AlN surface band bending into account. By taking the band gap of HfO 2 and AlN as 5.8 eV and 6.2 eV, respectively, a type-II band line-up was found between HfO 2 and AlN.

Polarization-Charge Inversion at Al2O3/GaN Interfaces through Post-Deposition Annealing

“…The interface charge densities at the Al2O3/GaN interfaces with PDA are also determined to be 1.73 × 10 13 cm −2 , 2.73 × 10 14 cm −2 , and 3.19 × 10 13 cm −2 for the samples B1, C1, and D1, individually, and 1.71 × 10 13 cm −2 , 8.38 × 10 14 cm −2 , and 4.81 × 10 13 cm −2 for the samples B3, C3, and D3, separately. The decrease in the interface charge density of D1 and D3 annealed at 900 °C, compared to that obtained at 700 °C, is possibly due to clean up effect of PDA to suppress the formation of Ga-O bonds [34][35][36]. In case of the reference GaN with no Al2O3, the interface charge density is determined to be 1.72 × 10 13 cm −2 according to the…”

“…The increased Ga-O/Ga-N ratio with the PDA at 500 °C and 700 °C is attributed to the diffusion of O atoms of Al2O3 into GaN. While, the reduction in Ga-O bonds of D3 annealed at 900 °C with respect to that of C3 at 700 °C could be ascribed to clean up effect of PDA to passivate Ga-O bonds, based on the difference in the magnitudes of negative Gibb's free energy of Al2O3 (-1582.3 kJ/mol) and Ga-O (-998.3 kJ/mol) [34][35][36]. The net area charge densities (σnet) at the Al2O3/GaN interfaces are calculated by the following Equation [8]:…”

Surface band bending in semimetal Td-WTe2

“…33 The principle and calculation method have been speci ed previously. [33][34][35][36] Brie y, a measured apparent core level spectrum is actually an integration of photoelectrons emitting from a depth of d 0 , and can be given by Declarations Figures Figure 1 (a) Ball model of Td-WTe2 with surface oxidation. (b) ADXPS measurement with TOA of θ on surface oxide layer containing WTex, WOx, TeOx.…”