A study of impurity state and its implication in inorganic and organic semiconductors

• Main Authors: Chi-Ken Lu, 陸紀亙
• Other Authors: Hsin-Fei Meng
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/92544263798589797212

博士 === 國立交通大學 === 物理研究所 === 95 === This dissertation is divided into two parts which both relate to the impurity in semiconductors. The first part deals with a solid state system which is able to generate THz radiation by the concept of resonant state. Such state is a hybrid state of a localized impurity state and a continuum. By numerically solving the Boltzmann kinetic equation, we are able to show that a population inversion is possible in a practical condition. The second part deals with the sensitive electronic properties of organic semiconductors to the presence of adsorbed oxygen molecules. There are mainly two questions in this part. One is the huge mobility imbalance among electron and hole carriers. We found that once an oxygen molecule adsorbed onto a defect site, the binding energies for trapped electron will increase while that for trapped hole remains. The asymmetric binding energies are the essence of such mobility imbalance. The other interesting effect by oxygen molecule is the p-doping which cause a undesired off-current in polymer field-effect transistors. Such doping is not able to reconcile with the low electron affinity of oxygen molecules. By calculating the band structure of an oxygenated polythiophene, we are able to clarify the dependence of doping on the ionization potential of host material and the conditional illumination.