Strong Two‐Dimensional Electron Gas at Crystalline and Amorphous InGaSnO Stack Interface for High Performance Transistors with High Temperature Stability

Abstract The self‐aligned, coplanar thin‐film transistors (TFTs) with dual‐channel, oxide semiconductors are reported for advanced integrated circuits (ICs) and displays. A Ga‐rich indium gallium tin oxide (IGTO) layer is deposited on In‐rich IGTO thin film to achieve high‐performance and stability TFT. The dual‐channel IGTO TFTs exhibit a threshold voltage of −0.20 V, field‐effect mobility of 56.75 cm ² V ⁻¹ s ⁻¹ , and subthreshold swing of 0.14 V dec ⁻¹ with negligible hysteresis. The stable performance under positive and negative bias temperature stress, as well as the negligible variation in electrical characteristics up to 200 °C, is attributed to the formation of strong 2D electron gas (2DEG) at the interface of two oxide semiconductors. A significant conduction band bending at the heterointerface between crystalline In‐rich IGTO and amorphous Ga‐rich IGTO is confirmed by TCAD simulation. This supports the formation of strong 2DEG. A 19‐stage pseudo‐CMOS ring oscillator is demonstrated with dual‐channel IGTO TFTs with the oscillation frequency of 9.03 MHz and a propagation delay of 2.91 ns at the applied voltage (V _DD ) of 10 V. The device performance changes very small at 200 °C, confirming that the proposed TFT is very suitable for application requiring high mobility with high temperature stability.