Study of Electrical and Optical Stability of GSZO THin Film Transisitors.

摘要

The growing need for large area display for home entertainment and the crossover to digital broadcasting has pushed the active matrix flat panel display industry to thrive over the past few years. The ability to make electronic devices that are transparent to visible and near infrared wavelengths with materials posing a high carrier mobility and high visual transparency is currently being researched. There has been a great interest in amorphous indium gallium zinc oxide (a-IGZO) as the active channel layer due to its promising electrical and photosensitive performance for thin film transistors with a high field-effect mobility, low drain off current and good uniformity that is compatible with the state-of-the-art Gen-8 substrate size. However, as indium resources are becoming scarce and expensive, replacing the a- IGZO TFT with a less expensive material such as gallium tin zinc oxide (GSZO) has shown a potential to have similar electrical behavior. One of the issues of the oxide TFT, in general, is the optical and electrical instability. Hence, we have carried out a systematic and detailed study on the electrical and optical stability of these TFTs as a function of annealing temperature, deposition pressure, film thickness and oxide thickness to gain better insight into the degradation mechanism of these transistors as well as to correlate to the initial performance of the device. The analysis of stability measurements indicated that the post deposition annealing temperature of 350 deg C has the dominant effect on the reduction of the deep and shallow states, thereby making the device more stable. This also explains the superior performance of the initial device. The low temperature annealed device at 140 C appears to be influenced by the deposition pressure. Thus, this work shows that there is considerable room for improvement in both the TFT performance as well as its stability by tailoring the deposition parameters.