Electron mobility enhancement in solution-processed low-voltage In2O3 transistors via channel interface planarization

Abstract

The quality of the gate dielectric/semiconductor interface in thin-film transistors (TFTs) is known to determine the optimum operating characteristics attainable. As a result in recent years the development of methodologies that aim to improve the channel interface quality has become a priority. Herein, we study the impact of the surface morphology of three solution-processed high-k metal oxide dielectrics, namely AlOx, HfOx, and ZrOx, on the operating characteristics of In2O3 TFTs. Six different dielectric configurations were produced via single or double-step spin-casting of the various precursor formulations. All layers exhibited high areal capacitance in the range of 200 to 575 nF/cm2, hence proving suitable, for application in low-voltage n-channel In2O3 TFTs. Study of the surface topography of the various layers indicates that double spin-cast dielectrics exhibit consistently smoother layer surfaces and yield TFTs with improved operating characteristics manifested, primarily, as an increase in the electron mobility (µ). To this end, µ is found to increase from 1 to 2 cm2/Vs for AlOx, 1.8 to 6.4 cm2/Vs for HfOx, and 2.8 to 18.7 cm2/Vs for ZrOx-based In2O3 TFTs utilizing single and double-layer dielectric, respectively. The proposed method is simple and potentially applicable to other metal oxide dielectrics and semiconductors.

Low‐Voltage Heterojunction Metal Oxide Transistors via Rapid Photonic Processing

“…A simple approach to overcome this issue is by using multilayer dielectrics. [ 22,33,34 ] Figure a shows a set of current–voltage ( J – V ) characteristics for metal–insulator–metal (MIM) devices based on photonically converted Al 2 O 3 /ZrO 2 bilayer as the dielectric. All devices show similar J – V characteristics with low leakage currents (<10 −5 A cm −2 ) and breakdown fields in the range 0.8‐1 MV cm −1 .…”

“…Bare aluminum (Figure 4a) exhibits a relatively rough surface with a root mean square roughness (σ RMS ) of 1.81 nm, which is common for thermally evaporated Al. [ 22 ] The surface of the photonically converted Al 2 O 3 layer appears amorphous and retains a relatively high surface roughness of σ RMS = 1.6 nm (Figure 4b). Subsequently deposited ZrO 2 , on the other hand (Figure 4c), exhibits significantly smoother surface with a drastically reduced σ RMS of 0.43 nm.…”

“…Subsequently deposited ZrO 2 , on the other hand (Figure 4c), exhibits significantly smoother surface with a drastically reduced σ RMS of 0.43 nm. The positive effect of channel interface planarization was investigated in our previous study [ 22 ] and is critical for the formation of a well‐defined transistor channel. Figures 4d,e shows the topography AFM images for the photonically processed In 2 O 3 and ZnO layers, respectively, atop the bilayer dielectric.…”

“…[ 20 ] To mitigate this problem and simultaneously achieve a high capacitance, the usage of homo‐ or heterojunction bilayer dielectric layers was suggested. [ 21,22 ] We adopted a similar approach and explored the use of Al 2 O 3 /ZrO 2 bilayer dielectric layers. The bilayer gate dielectric of Al 2 O 3 /ZrO 2 was first grown on aluminum (Al) gate electrodes via sequential spin coating and flash annealing (for a duration of 16 s).…”

Enhanced Electrical Performance and Stability of La‐Doped Indium Oxide‐Based Thin‐Film Transistors and Application Explorations

“…[ 2,3 ] Among these oxides, In 2 O 3 has become the potential candidate due to its high carrier mobility, excellent optical transmittance, and large bandgap value. In spite of the improved electrical properties of In 2 O 3 ‐based TFTs, [ 4–6 ] the issue of instability is still outstanding. Therefore, it is particularly important to find ways to improve the stability and thus reduce the impact of the resulting threshold voltage shift on the practical application of TFTs.…”