Trapping levels in nanocrystalline porous silicon

Abstract

Trapping levels in fresh (one month) and naturally aged (one year) nanocrystalline porous silicon have been investigated using the optical charging spectroscopy method. Four significant maxima and/or shoulders were observed for fresh samples and five for aged ones. They have been attributed to five and six trapping levels, respectively. The trapping centers corresponding to the most shallow four levels are situated at or nearby the internal surface of the porous silicon films.

Trapping phenomena in silicon-based nanocrystalline semiconductors

“…and that the horizontal trap distribution can be considered as homogeneous [13,15]. The samples were studied by TSDC and OCS methods.…”

“…The OCS measurements performed on nc-PS are presented in Fig. 3 [13]. 1 In this figure, it is shown the discharge currents measured on a fresh sample for (a) weakly (k = 1.0 lm) and (b) strongly (k = 0.5 lm) absorbed light charging.…”

“…This sign changes if the level following the discharging one correspond to opposite sign carriers. Then it is possible that a supplementary (''false'') maximum with opposite sign appears [13,15]. This kind of maximum can easily be identified by the fact that its apparent activation energy is bigger than that of the following maximum.…”

“…Our group thoroughly studied the traps in nanocrystalline porous silicon (nc-PS) by optical charging spectroscopy (OCS) and thermally stimulated depolarization currents (TSDC) methods [13][14][15][16]. We have also made some OCS and TSDC measurements on multi-quantum well (MQW) structures formed by a set of q = 50 bilayers of nc-Si and CaF 2 deposited on silicon substrate (nc-Si/ CaF 2 ) 50 [17,18].…”

Silicon nano-crystalline structures fabricated by a sequential plasma hydrogenation and annealing technique

“…After the initial observation of photoluminescence from porous silicon layers by Canham [16], a considerable number of studies have been carried out on the properties of porous silicon materials including their structure, temperature dependence and electroluminescence properties [17][18][19][20][21]. Based on these investigations, several mechanisms have been suggested for the PL behavior of porous silicon layers.…”