From Event: SPIE Organic Photonics + Electronics, 2016
Organic field-effect transistors (OFET) are important elements in thin-film electronics, being considered for
flat-panel or flexible displays, radio frequency identification systems, and sensor arrays. To optimize the
devices for high-frequency operation, the channel length, defined as the horizontal distance between the
source and the drain contact, can be scaled down. Here, an architecture with a vertical current flow, in particular the
Organic Permeable-Base Transistors (OPBT), opens up new opportunities, because the effective transit
length in vertical direction is precisely tunable in the nanometer range by the thickness of the semiconductor
layer. We present an advanced OPBT, competing with best OFETs while a low-cost, OLED-like fabrication
with low-resolution shadow masks is used (Klinger et al., Adv. Mater. 27, 2015). Its design consists of a stack
of three parallel electrodes separated by two semiconductor layers of C60 . The vertical current flow is
controlled by the middle base electrode with nano-sized openings passivated by an native oxide.
Using insulated layers to structure the active area, devices show an on/off ratio of 10⁶ , drive 11 A/cm² at an
operation voltage of 1 V, and have a low subthreshold slope of 102 mV/decade. These OPBTs show a unity
current-gain transit frequency of 2.2 MHz and off-state break-down fields above 1 MV/cm. Thus, our
optimized setup does not only set a benchmark for vertical organic transistors, but also outperforms best
lateral OFETs using similar low-cost structuring techniques in terms of power efficiency at high frequencies.
Markus P. Klinger, Axel Fischer, Felix Kaschura, Reinhard Scholz, Björn Lüssem, Bahman Kheradmand-Boroujeni, Frank Ellinger, Daniel Kasemann, and Karl Leo, "Organic permeable-base transistors - superb power efficiency at highest frequencies
(Conference Presentation)," Proc. SPIE 9943, Organic Field-Effect Transistors XV, 99430I (Presented at SPIE Organic Photonics + Electronics: August 30, 2016; Published: 2 November 2016); https://doi.org/10.1117/12.2237719.5168997894001.
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