Conductance measurements on P-b centers at the (111)Si:SiO2 interface

The electrical properties of the P-b center have been measured using the conductance technique over the temperature range 130-290 K. A high concentration of P-b centers was created by vacuum annealing of 28-nm-thick thermal oxides on (111) silicon surfaces. Fitting the conductance data allowed the contribution of the (0/-) P-b level to be separated from the U-shaped background states. The (0/-) peak in the density of states was found to be asymmetrical with a broad shoulder on the conduction band side. The P-b levels were found to show a capture cross section which fell toward the band edges and which could be fitted by assuming an activated cross section with an activation energy which increased toward the band edges. By contrast, the background states showed a cross section which was temperature and band bending independent.