Carrier conduction in heterojunction of hydrogenated nanocrystalline silicon with crystal silicon

Abstract

Phosphorus-doped hydrogenated nanocrystalline silicon (n-type nc-Si:H) film was deposited by plasma enhanced chemical vapor deposition technique on heavy doped p-type crystalline silicon ((p +)c-Si) substrate to form heterojunction of (n)nc-Si:H/(p +)c-Si. In electrical experiments, both negative resistance in forward current–voltage ( I–V) measurements and current staircases in reverse I–V experimental data were observed from this structure of (n)nc-Si:H/(p +)c-Si at 77 K, which reveals it as a semiconductor heterojunction tunnel diode. The forward current is assigned to interband tunneling, excess and thermionic emission component, respectively. Within reverse bias voltage range from 0 to around − 13 V, the reverse current can be ascribed to minority carriers instead of majority carriers tunneling across the depletion layer in heterojunction. Cross reverse applied voltage range from − 13 to about − 37 V, the reverse current can be attributed to injection of electrons via sequent resonant tunneling through Si nanocrystals into substrate. As further increasing reverse applied voltage, the reverse current can be allocated to carrier avalanche multiplication within amorphous buffer layer region to enhance electron resonant tunneling in nc-Si:H layer.