DETERMINATION OF MIDGAP DENSITY OF STATES IN a-Si : H USING SPACE-CHARGE-LIMITED CURRENT MEASUREMENTS

Abstract

The density of states in glow discharge deposited amorphous silicon has been deduced from space-charge-limited (SCL) current measurements on samples with an n+-i-n+ sandwich configuration. The temperature and filmthickness dependence of the SCL current are found to be consistent with the theory of one-carrier steady-state SCL current flow. The resulting midgap density of states is 1016-4.1016 cm-3 eV-1 in the energy region 0.75 to 0.6 eV below the conduction band edge. This figure is lower than that usually found by the field-effect technique (~1017 cm-3 eV-1), probably due to the inclusion of interface states in field-effect measurements