Conduction mechanisms in porous Si LEDs

Diode-like structures were prepared from p- and n-type Si, in which porous Si layers were sandwiched between the crystalline Si and the evaporated Al top contact. The current-voltage characteristics were investigated in that bias polarity, at which electroluminescence occurs. It was found that the characteristics follow the Fowler-Nordheim tunneling process for both type of devices. The tunneling occurs through the heterojunction barrier at the crystalline-porous interface. The leakage current experienced at low biases in the p-type structure is attributed to trap-assisted tunneling; its saturation character was pointed out by low-frequency noise measurements.