Instability studies in amorphous silicon based alloys

Özdemir, Orhan
The pixel element which is an integrated combination of a p-i-n diode with a thin film transistor (TFT) is used to produce image sensor arrays in scanning and displays technologies, necessitating the deposition of hydrogenated silicon based semiconducting and insulating thin films such as a-Si:H, a-SiNx:H over large area. The widely used techniques to achieve this goal is the plasma enhanced chemical vapor deposition (PECVD) due to its large area and low temperature (? 300 ?C) abilities. In particular, PECVD has proved to be able to deposit both high quality insulator (a-SiNx:H) and active layer of p-i-n diode (intrinsic hydrogenated amorphous silicon carbide, a-SiCx:H) and by sequential deposition, it is possible to minimize the interface related problems, which play an important role in metal insulator semiconductor (MIS) and TFT structures. PECVD deposited a-SiCx:H films over p-type crystal Si and metal substrates (MIS and MIM) were investigated by both admittance spectroscopy (Capacitance or conductance vs. voltage, temperature or frequency measurements) and Deep Level Transient spectroscopy (DLTS) to investigate the interface related problems. In this respect, instability phenomena (due to the creation of metastable states and charge injection into the gate electrode) were studied via the c-Si/a-SiCx:H (and/or a-SiNx:H) heterojunction. Specially, capacitance voltage kinetics were worked out and then the enrolled trap energies were identified with temperature mode DLTS. The expertise gathered as a result of these studies were used in the fabrication and characterization of TFT2s. In this respect, inverted gate staggered type Thin Film Transistor produced and characterized for the first time after Combo-251 Pattern Generator was implemented.


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Citation Formats
O. Özdemir, “Instability studies in amorphous silicon based alloys,” Ph.D. - Doctoral Program, Middle East Technical University, 2004.