Modulating Thin Film Transistor Characteristics by Texturing the Gate Metal

Abstract

The development of reliable, high performance integrated circuits based on thin film transistors (TFTs) is of interest for the development of flexible electronic circuits. In this work we illustrate the modulation of TFT transconductance via the texturing of the gate metal created by the addition of a conductive pattern on top of a planar gate. Texturing results in the semiconductor-insulator interface acquiring a non-planar geometry with local variations in the radius of curvature. This influences various TFT parameters such as the subthreshold slope, gate voltage at the onset of conduction, contact resistance and gate capacitance. Specific studies are performed on textures based on periodic striations oriented along different directions. Textured TFTs showed upto ±40% variation in transconductance depending on the texture orientation as compared to conventional planar gate TFTs. Analytical models are developed and compared with experiments. Gain boosting in common source amplifiers based on textured TFTs as compared to conventional TFTs is demonstrated.

Geometric influence of cylindrical surface curvature on the electrostatics of thin film transistors

“…Upto ±40% variation in transconductance was observed depending on the texture orientation as compared to conventional planar gate TFTs in a-Si:H technology. Demonstrations of high gain common-source amplifiers using textured TFTs have also been reported [35]. Patterning the gate with dimples in organic (P3HT) TFTs showed almost 400% improvement in current [34].…”

“…Thin film transistors (TFTs) on flexible substrates promise applications such as bendable sensors and actuators [1][2][3][4][5][6][7][8][9][10][11], flexible energy harvesters [12][13][14][15] and wearable devices for health diagnostics [16][17][18][19][20][21]. In the recent past, there has been a drive towards developing TFTs on rough surfaces such as textiles [22][23][24], threads and fibers [17,25], paper [26][27][28][29][30][31][32][33] and artificially corrugated surfaces [34][35][36][37]. In such cases, the metalinsulator-semiconductor (MIS) stack of the TFT may experience significant geometric curvature.…”

“…High curvature geometry of the MIS stack results in changing the gate electric field distribution from nearly uniform to non-uniform. The importance of geometry on the performance of TFTs is seen from experiments performed on TFTs deposited on artificially engineered rough surfaces [34][35][36][37]. In these experiments, the gate metal of the TFT was undulated in both convex and concave fashions by the use of corrugations or dimples.…”

Wire-Based Core Field Effect Transistor (CoreFET)

“…Thin film transistors (TFTs) are generally made up of a geometry with a bottom gate and a top drain/source. Studies on modulating TFTs by changing gate texture [9] and curvature [10] have also been reported. Most of the existing FETs are fabricated using micromanufacturing processes that are time-consuming and expensive.…”