Surface roughness

Electrical engineering

Subthreshold conduction

Transistor

Organic chemistry

Subthreshold slope

Electron mobility

Field-effect transistor

Engineering

Voltage

Composite material

Chemistry

Materials science

Amorphous solid

Field effect

Optoelectronics

IEEE Transactions on Electron Devices

Amorphous indium&#x2013;gallium&#x2013;zinc oxide (a-IGZO) is a promising channel material for an upper transistor in monolithic three-dimensional devices. Although the field-effect transistors (FETs) with a rather thick channel thickness &#x003E;10 nm have been intensively examined, less information is available for the IGZO FETs with an ultra-thin body (&#x003C; 10 nm). In this study, the FETs with the IGZO channel layer ranging from 2 to 20 nm were investigated in detail. As the channel thickness decreased from 20 to 7 nm, the mobility and subthreshold swing (SS) values were improved. In contrast, the deterioration in mobility and SS occurred when the IGZO thickness was less than 7 nm. The physical rationale for the strong IGZO thickness dependence on performance of the resultant FETs was discussed based on subgap density-of-state distribution and mobility models such as percolation and surface-roughness scattering mechanisms using a technological computer-aided design simulation with a quantum mechanical model. IGZO FET with an IGZO thickness of 7 nm exhibited the best performance, which was attributed to the synergic balance by percolation efficiency and reduction in effective subgap defect density of IGZO.

Effect of Channel Thickness on Performance of Ultra-Thin Body IGZO Field-Effect Transistors