Gallium oxide/indium gallium zinc oxide heterojunction Schottky barrier thin-film transistors with ultrahigh 2D electron density over 6 × 1013/cm2

To enhance the current driving capability of oxide semiconductor thin-film transistors (TFTs) is a key challenge in emerging display applications that request high resolution and brightness, such as micro-light-emitting diode. In general, increasing the indium content in indium gallium zinc oxide (IGZO) to achieve high mobility is the most common method, but indium-rich IGZO TFTs suffer from negative threshold voltage (VTH) and poor stability. In this work, a novel high on-current enhancement-mode Schottky barrier TFT is fabricated through the Ga2O3/IGZO heterojunction and Ni/IGZO Schottky junction. A high-density two-dimensional electron gas with sheet carrier density over 6 × 1013/cm2 is achieved, by introducing an oxygen-vacancy-rich Ga2O3/IGZO interface. The sheet carrier density is beyond the gate control limitation, leading to a low channel resistance. The source/drain Schottky junction is achieved through defect engineering by Ga2O3 growth and etching at the Ni/IGZO interface. The Schottky barrier can be modulated by gate voltage so that the device can be turned off with a large VTH of ∼1 V. The proposed Ga2O3/IGZO Schottky barrier heterojunction TFT enables a new approach to enhance the current driving capability of oxide TFTs beyond conventional material engineering for high mobility.