NEGATIVE-RESISTANCE EFFECTS IN LIGHT-EMITTING POROUS SILICON DIODES

Definite negative-resistance (NR) effects in electroluminescence(EL)-e missive porous silicon (PS) diodes have been investigated in relation to the EL characteristics. The PS diode is composed of a semitranspare nt thin Au film, a relatively thin PS layer, a n(+)- or p-type Si subs trate and an ohmic back contact. When the forward bias voltage is appl ied to the diode, a reversible NR behavior is observed in the current- voltage (I-V) characteristics at room temperature. At a low temperatur e of 10 K, the peak-to-valley current ratio in the n(+)-type substrate case extends to about 10(4). It is shown that the EL emission is swit ched on at the onset of the NR effect. For the p-type substrate diode, the NR effects can be activated by photoillumination. The mechanism o f the observed NR effects is also discussed from the viewpoint of elec tron injection into the silicon nanocrystallites in PS. The NR effects can be regarded as one of the field-induced functions of PS as a quan tum-sized crystalline system.