Transient photocurrent behavior in amorphous thin film heterostructures

The characteristics of transient photocurrent in amorphous heterostructures Al-As0.40S0.30Se0.30/Ge0.09As0.09Se0.82/Ge0.30As0.04S0.66–Al in the case of the positive polarity of the applied voltage at the top illuminated Al electrode are presented and discussed in this paper. The complex structure of the spectral distribution of the stationary (Fig. 1) and the transient (Fig. 3) photocurrent characteristics can be assigned to the different values of the optical band gap Eg of the involved amorphous layers (about Eg ~ 2.0 eV for As0.40S0.30Se0.30 and Ge0.09As0.09Se0.82; about Eg ~ 3.0 eV for Ge0.30As0.04S0.66). It is found that the dependence of photocurrent on light intensity has a power-law behavior Ipc ~ Fα(1.0 ≤ α ≤ 0.5), which is characteristic of amorphous semiconductors with an exponential distribution of localized states in the band gap.