Effect of Defect Sites in Charge Carrier Mobility Enhancement of Hopping Model

Charge carrier mobility in disorder materials was described by hopping model and the increasing in the mobility value of existing defect or impurity sites was investigated by Monte Carlo simulation of the rectangular hopping site. In the case of equal tunneling rate, the mobility value increases when the defect sites have higher energy and becomes saturate at the site energy about 1.04 times of the host energy. It found that the maximum mobility occurs when there are defect sites about 40 percents. When the tunneling rate to the defect site is reduced the maximum mobility occurs at higher percent of defect sites. In addition the other type of mobility enhancement appears when the defect site has energy lower than 0.92 times of the host site energy and this occurs only at small amount of the defect sites (less than 10 percents). This type of the enhancement exhibits much higher value of the carrier mobility and the result indicates the mobility value up to about three times of the host value.