ZrSiOx/IGZO heterojunctions band offsets determined by X-ray photoelectron spectroscopy

• We measured the valence band offsets for ZrSiOx on amorphous InGaZnO4.
• A value of −0.12 eV was determined from XPS measurements, with a staggered Type II alignment.
• The conduction band offset can then be derived as 2.86 eV.
• These values are compared with those of other dielectrics on InGaZnO4.

We measured the valence band offset of sputtered ZrSiOx (bandgap 5.9 eV) on InGaZnO4 (IGZO) using X-ray photoelectron spectroscopy and the bandgaps of these materials using either absorption or reflection electron energy loss spectroscopy. This enabled us to additionally derive the conduction band offsets. We examined the effect of venting the samples prior to dielectric deposition on the band offsets compared to keeping them in vacuum. The ZrSiOx/IGZO system has a staggered, type II alignment, with a valence band offset of −0.12 eV ± 0.04 eV for samples in which all the layers were kept in vacuum or −0.05 eV for samples exposed to atmosphere prior to the measurement. The conduction band offset for ZrSiOx/IGZO was derived as 2.86 eV for the vacuum samples from the measured bandgap of the IGZO (3.16 eV) and 2.93 eV for vented samples. The small valence band offsets in this system are consistent with past reports that ZrO2/IGZO has essentially no valence band offset.