Al2O3∕InGaZnO4 Heterojunction Band Offsets by X-Ray Photoelectron Spectroscopy

The use of Al 2 O 3 as a gate dielectric has been shown to improve the performance and electrical stability of α-InGaZnO 4 (IGZO) thin film transistors. X-ray photoelectron spectroscopy (XPS) was used to measure the energy discontinuity in the valence band (Δ E v ) of Al 2 O 3 /IGZO heterostructures deposited by sputtering at <50°C, respectively. A value of Δ E v = 0.95 ± 0.17 eV was obtained by using the In 2p3/2, Zn 2p3/2 and 3d5/2 energy levels as references. Given the experimental bandgap of 3.2 eV for the IGZO, this would indicate a conduction band offset of 2.35 eV in this system.