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.