The growing demand for TFT backplanes on rigid and flexible substrates necessitates compact, yet accurate, models of TFT operation and corresponding parameter extraction techniques to expedite the design of new pixel circuits. Here, the impact of non-idealities such as contact resistance and interface properties must be considered so as to establish a meaningful relation between the device characteristics and material properties. This is particularly true for circuits on flexible substrates, where knowledge of the strain modulation of the TFT characteristics is invaluable in the design of mechanically immune circuits.

This thesis addresses these challenges. Speciflcally, it presents compact modelling of the static and dynamic characteristics of TFTs. The model is physically based and involves a minimal set of parameters. The associated techniques for parameter extraction, which turn out to be more complex than those of the crystalline silicon fleld-effect transistors are also presented. Here, non-idealities such as the contact resistance are systematically examined, since they can change by orders of magnitude due to process variations that strongly influence the extracted parameters. A new definition of device mobility figff is presented, which takes into account both the free and trapped carriers and holds for disordered semiconductors with an exponential band tail such as a-Si:​H. Moreover, the new definition is able to account for the voltage and temperature dependence of conductivity. A good agreement between the modelling and measurement results is obtained with a discrepancy of less than 2%.

Using experimental results and physical modelling, we examine the sensitivity of the TFT parameters to strain to obtain insight into the physics of a-Si;​H and its elastoresistance properties. Subsequently, the eflPects of strain are incorporated into the TFT model for the analysis and design of the circuits with a reduced strain sensitivity. Here, we illustrate that the current mirror circuit, which exhibits a sufficient immunity to mechanical strain, clearly demonstrates how the material shortcomings and environmental disturbances can be compensated for by circuit techniques.