Hot electron spectroscopy for intrinsic Schottky barrier determination at metal–InGaZnO interfaces

In this Letter, a three-terminal hot electron transistor is developed to explore the energy alignment between metal and amorphous indium–gallium–zinc oxide (a-IGZO). Utilizing detailed analysis of the hot electron current as a function of the applied bias voltage, the intrinsic Schottky barrier height is precisely determined at 1.2 eV between metal contact (Au) and a-IGZO. Systematic reduction of the sputtering oxygen flow rate during a-IGZO film deposition from 6 to 4.5 sccm and subsequently to 3 sccm resulted in a progressive decrease in the Schottky barrier height to 0.94 and 0.85 eV, respectively. This could be attributed to the increased concentration of oxygen vacancies in a-IGZO, which induces changes in bandwidth as confirmed by further ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy characterizations. Compared to the methods of traditional thermionic emission theory and Fowler–Nordheim tunneling model to extract Schottky barrier height, this study provides a more feasible approach for evaluating the barriers at the metal–semiconductor interface.