Leveraging Contact Effects for Field-Effect Transistor Technologies with Reduced Complexity and Superior Current Uniformity

Abstract

In order to achieve high performance, the design of devices for large-area electronics needs to be optimized despite material or fabrication shortcomings. In numerous emerging technologies thin-film transistor (TFT) performance is hindered by contact effects. Here, we show that contact effects can be used constructively to create devices with performance characteristics unachievable by conventional transistor designs. Source-gated transistors (SGTs) are not designed with increasing transistor speed, mobility or sub-threshold slope in mind, but rather with improving certain aspects critical for real-world large area electronics such as stability, uniformity, power efficiency and gain. SGTs can achieve considerably lower saturation voltage and power dissipation compared to conventional devices driven at the same current; higher output impedance for over two orders of magnitude higher intrinsic gain; improved bias stress stability in amorphous materials; higher resilience to processing variations; current virtually independent of source-drain gap, source-gate overlap and semiconductor thickness variations. Applications such as amplifiers and drivers for sensors and actuators, low cost large area analog or digital circuits could greatly benefit from incorporating the SGT architecture.

Source-gated transistors for order-of-magnitude performance improvements in thin-film digital circuits

“…This device concept is now being studied in a multitude of material systems25272829303132333435 after first being identified as having different operation to conventional, and indeed Schottky-barrier, field-effect transistors by Shannon and Gerstner19. In reality, as SGT structure is very similar to a conventional FET and in many technologies it is easier to obtain a SGT than a FET, SGTs have been observed36 without explanation37 much earlier.…”

“…The source-gated transistor (SGT) 18 19 20 21 , a device suitable for LAE, allows improved energy efficiency 22 , bias stress stability 23 , tolerance to process variations 24 and gain 22 25 26 to be achieved in analog circuits with minimal changes to standard fabrication processes. This device concept is now being studied in a multitude of material systems 25 27 28 29 30 31 32 33 34 35 after first being identified as having different operation to conventional, and indeed Schottky-barrier, field-effect transistors by Shannon and Gerstner 19 . In reality, as SGT structure is very similar to a conventional FET and in many technologies it is easier to obtain a SGT than a FET, SGTs have been observed 36 without explanation 37 much earlier.…”

Temperature dependence of the current in Schottky-barrier source-gated transistors

“…Both digital 15 and analog applications 14,[16][17][18][19] could benefit from using these devices, in terms of amplification, energy efficiency, uniformity of electrical performance, and reliability. Figure 1 b and c…”