Electrical and photoelectric characteristics of n-Si/porous silicon/Pd diode structures and the effect of gaseous hydrogen on them

The current-voltage characteristics and the photovoltage of Pd/por-Si/n-Si diode structures in the temperature interval 106-300 K are investigated. The forward branch of the I-V characteristic at room temperature is exponential, with a nonideality factor n greater than or similar to 12. The dependence of the current on the voltage at a low temperature and a high injection level is a power function with an exponent equal to 4.1. Amplification of the photocurrent is detected as the reverse bias increases; the gain reaches 10(3) at 106 K when the bias was more than 10 V. It is concluded that a double charge-carrier injection mechanism predominates during charge transfer through the porous layer. When gaseous hydrogen acts on the structure, the photovoltage decreases by three orders of magnitude, while the dark current decreases by an order of magnitude. The structures studied here are characterized by significant relaxation times of the increase of the currents and the recovery of the currents and the photovoltage after the action of hydrogen. The effect of hydrogen on the photoelectric characteristics is associated with the formation of an additional dipole layer at the Pd/por-Si boundary, which lowers the Schottky barrier. (C) 1999 American Institute of Physics. [S1063-7826(99)01803-7].