Fabrication and Modeling of Ambipolar Hydrogenated Amorphous Silicon Thin Film Transistors.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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The hydrogenated amorphous silicon a-SiH thin film transistor TFT has been studied extensively for several years. Its application as a switching element in large area liquid crystal display arrays has been demonstrated. Modeling studies have been performed to quantify and explain the performance of the a-SiH TFT. However, throughout these investigations little has been reported concerning the ambipolar nature of the a-SiH TFT that is, the ability of the device to operate alternatively as an n-channel or a p-channel device. The work described in this thesis extends the previous by specifically addressing the ambipolar behavior of the a-SiH TFT. In particular, a process sequence has been developed to fabricate high quality ambipolar a-SiH TFTs with emphasis on ohmic sourcedrain contacts. Using experimental data from these devices and TFT theory, a model has been developed for obtaining the output drain current vs. drain voltage of ambipolar a-SiH TFTs. The model involves the numerical integration of an interpolated sheet conductance function. By using the appropriate flat-band voltage, the model accurately predicts the experimental output drain current characteristics for both n- and p-type operation over many orders of magnitude.
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- Solid State Physics