UBC Theses and Dissertations
An investigation of defects in gallium arsenide using the DLTS technique Shi, Yi
A well-known technique—Deep level Transient Spectroscopy (DLTS)—was used for investigating deep levels in Gallium Arsenide (GaAs) semiconductor material. Eight deep levels, among them the most important deep level EL2, were found in Liquid-Encapsulated Czochralski (LEC) grown semi-insulating GaAs substrates. Two of these deep levels, one electron deep level and one hole deep level, were observed for the first time in DLTS studies. Both have large thermal activation energy. A study in understanding the formation of deep levels in the GaAs substrate was actively undertaken. The cause of four deep levels present in the LEC-grown GaAs substrate were identified. The chief effects on electronic devices and integrated circuits due to the presence of these deep levels in the GaAs substrate were partially characterized. Other contributions include: firstly, a computer-assisted method was used to profile the spatial distribution of deep traps. Deep traps act as free carrier traps when deep levels are present in semiconductor bulk material. Secondly, the author, through experiments, made clear that the increasing capacitance of a Schottky diode increasing with temperature was due to the Schottky diode's barrier height decreasing with rising temperature. Thirdly, the author, by experimental results, supported the point that shallow donor with very high concentration in the bulk material is the major cause of annihilation of EL2 deep traps.
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