Determination of the Band Alignment of a‐IGZO/a‐IGMO Heterojunction for High‐Electron Mobility Transistor Application

Abstract

In the past decade, amorphous InGaZnO thin film transistors (a‐IGZO TFTs) have become a very promising candidate for application in flat panel displays (FPDs). However, it is difficult to break through the mobility bottleneck of a‐IGZO TFTs to obtain mobilities higher than 100 cm2 V−1 s−1, thus limiting their use in more advanced applications. Construction of a high‐electron mobility transistor (HEMT) based on a heterojunction structure could provide a solution for this problem. In this work, the band alignment of a‐IGZO and amorphous InGaMgO (a‐IGMO) heterojunction has been investigated using X‐ray photoelectron spectroscopy (XPS) and transmission spectra measurements. The valence band (ΔEV) and conduction band offsets (ΔEC) were determined as 0.09 and 0.83 eV, respectively. The ΔEC was large enough to construct a potential well that could favor the appearance of a two‐dimensional electron gas (2DEG). Hence, the achievement of an HEMT based on a‐IGZO/a‐IGMO heterojunction can be expected. Moreover, band bending contributed greatly to such a large ΔEC, and thus to the formation of electrical confinement structure. Our findings suggest that a‐IGZO/a‐IGMO heterojunction is a potential candidate for constructing a HEMT and thus breaking through the mobility bottleneck of a‐IGZO‐based TFTs for the applications in next‐generation electronic products.