How the application of commercial (thin film) flat panel display technology, used in the production of flexible displays and flexible digital X-ray detectors, can also be applied to reduce the ...manufacturing cost of wearable biomedical devices, as well as potentially improve their diagnostic functionality, is explored. As a technology platform to evaluate the presented new concept, a prototype photoplethysmograph biosensor using a flexible organic light-emitting diode display and pin photodiode (thin film) sensor technology for optical heart rate monitoring is developed.
This letter describes a method to identify the channel region of hydrogenated amorphous silicon thin film transistors (a-Si:H TFTs) in which threshold voltage(V th ) degradation occurs. The TFTs are ...subjected to gate bias stress under different operating conditions. Asymmetry in the measured TFT drain current in the forward direction (same source and drain during stress and measurement) and reverse direction (interchanging the source and drain terminals) shows localization of the gate-voltage dependent V th shift mechanism. Based on the observations, a charge-based expression for V th shift is derived.
Amorphous oxide semiconductor thin-film transistors on flexible plastic substrates typically suffer from performance and stability issues related to the maximum processing temperature limitation of ...the polymer. A novel device architecture based on a dual active layer enables significant improvements in both performance and stability. Device fabrication occurs below 200°C on a polyethylene naphthalate (PEN) substrate using mixed metal oxides of either zinc indium oxide (ZIO) or indium gallium zinc oxide (IGZO) as the active semiconductor. The dual-active-layer architecture allows for adjustment in the saturation mobility and threshold voltage stability without the requirement of high-temperature annealing, which is not compatible with flexible plastic substrates. The device performance and stability is strongly dependent on the composition of the mixed metal oxide; this dependence provides a simple route to independently adjust the threshold voltage stability and drive performance. By switching from a single to a dual active layer, the saturation mobility increases from 1.2 to 18.0 cm 2 /V·s , whereas the rate of the threshold voltage shift decreases by an order of magnitude. This approach could assist in enabling the production of devices on flexible substrates using amorphous oxide semiconductors in the near future.
This paper reviews amorphous silicon thin-film-transistor (TFT) degradation with electrical stress, examining the implications for various types of circuitry. Experimental measurements on ...active-matrix backplanes, integrated a-Si:H column drivers, and a-Si:H digital circuitry are performed. Circuit modeling that enables the prediction of complex-circuit degradation is described. The similarity of degradation in amorphous silicon to negative bias temperature instability in crystalline PMOS FETs is discussed as well as approaches in reducing the TFT degradation effects. Experimental electrical-stress-induced degradation results in controlled humidity environments are also presented.
Mixed-oxide thin-film transistors (TFTs) have been extensively researched due to their improved stability under electrical bias stress compared to amorphous-silicon TFTs. However, there are many ...challenges before they can reach the manufacturing stage. At the Flexible Display Center (FDC), Arizona State University, Tempe, we are developing a low temperature indium-zinc-oxide (IZO) TFT process suitable for flexible substrates such as polyethylene naphthalate (PEN). We report the effect of bias stress on the performance of these IZO TFTs and compare it with a-Si:H TFTs. We also report the design and fabrication of a 3.8-in QVGA electrophoretic display on PEN substrate using IZO TFT backplane.
Future flexible OLED displays for army applications Forsythe, E.W.; Shi, J.; Liu, S. ...
2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum electronics and Laser Science Conference
Conference Proceeding
Organic light emitting diodes have been fabricated on an active matrix backplane from an 180C processed amorphous Si thin film transistors on polyethylene naphthalate (PEN) substrates. Organic light ...emitting diodes have been fabricated on the active matrix backplane. The presentation will include organic material development from ARL in the context of future Army applications.
This brief presents a novel approach to modeling gate bias-induced threshold-voltage (V@@dth@) degradation in hydrogenated amorphous silicon thin-film transistors (TFTs). The V@@dth@ degradation ...model is added to the SPICE 3.0 TFT device model to obtain a composite model and is verified by comparing the simulated V@@dth@ shift with measured data in a TFT latch circuit.
This brief presents a novel approach to modeling gate bias-induced threshold-voltage (V th ) degradation in hydrogenated amorphous silicon thin-film transistors (TFTs). The V th degradation model is ...added to the SPICE 3.0 TFT device model to obtain a composite model and is verified by comparing the simulated V th shift with measured data in a TFT latch circuit.
This brief presents a novel approach to modeling gate bias-induced threshold-voltage (V sub(th)) degradation in hydrogenated amorphous silicon thin-film transistors (TFTs). The V sub(th) degradation ...model is added to the SPICE 3.0 TFT device model to obtain a composite model and is verified by comparing the simulated V sub(th) shift with measured data in a TFT latch circuit.
