Samir Chatbouri

Traps contribution on detection time of single electron photodetector (Photo-SET)

In this paper we report charge trapping effect in a few number of nanocrystals silicon (2–4 nc-Si) embedded in SiO2 layer tunnel oxide of small area single electron photodetector (Photo-SET or nanopixel). The device detection time which estimated using capacitance versus time (C–t) measurements gives us a detection time about 350 s at T = 280 K. Capacitance versus voltage (C–V–T) measurements as a function of temperature confirm the presence of thermally activated trap centers localized at the tunnel oxide layer (trap activation energy: Ea ~ 0.41 eV and capture section: σ ~ 1.72 × 10−17 cm2). It is found that traps contribute to determine the detection process state where a threshold voltage shift of 60 mV at T = 280 K which corresponds to the trapping of one electron in the nc-Si dot. This process is probably due to the dominance of tunneling of electrons from traps level to the poly-Si/SiO x = 1.5 interface via the nc-Si. The Photo-SET estimated detection time is influenced by oxide traps.

Direct exchange between silicon nanocrystals and tunnel oxide traps under illumination on single electron photodetector

In this paper we present the trapping of photogenerated charge carriers for 300 s resulted by their direct exchange under illumination between a few silicon nanocrystals (ncs-Si) embedded in an oxide tunnel layer (SiOx = 1.5) and the tunnel oxide traps levels for a single electron photodetector (photo-SET or nanopixel). At first place, the presence of a photocurrent limited in the inversion zone under illumination in the I–V curves confirms the creation of a pair electron/hole (e–h) at high energy. This photogenerated charge carriers can be trapped in the oxide. Using the capacitance-voltage under illumination (the photo-CV measurements) we show a hysteresis chargement limited in the inversion area, indicating that the photo-generated charge carriers are stored at traps levels at the interface and within ncs-Si. The direct exchange of the photogenerated charge carriers between the interface traps levels and the ncs-Si contributed on the photomemory effect for 300 s for our nanopixel at room temperature.

Design of a Single-Electron Memory Operating at Room Temperature

Single-electronic transistors (SETs) are considered as the attractive component for the next generation of transistors due to their ultrasmall size and low power consumption. Because SETs with single island cannot work at high temperature normally, more researchers begin to carry out research on the SETs with N-dimension multi-islands. In this paper, we introduce a new architecture of single-electron memory; ideally the memory should operate in combination of SETs with a nanowire of two-dimensional regular array of multiple tunnel junctions (MTJs). This structure is analyzed and studied with Monte Carlo simulator, SIMON. The Coulomb blockade effect and thermionic effect play an important role in carrier conduction in the system at room temperature. Nanowire MTJs are used as an electrometer to sense the memory-node charge. The well-defined parameter in tunnel junction circuits helps to obtain the charging of single electrons in these circuits at room temperature.

Theoretical Analysis and Characterization of Multi-Islands Single-Electron Devices with Applications

A two- (2D) and three-dimensional (3D) multiple-tunnel junctions array is investigated. Device structure and electrical characteristics are described. We present a comparison of carriers transport through devices based on polymetallic grains based on master equation and the orthodox theory. The Coulomb blockade effect of 2D and 3D arrays is observed at low and high temperatures. The conduction mechanism is handled by the tunnel effect, and we adopt in addition the thermionic and Fowler-Nordheim emissions. Numerical simulation results focused on flash-memory and photodetector applications. Memory characteristics such as program/erase select gate operation are demonstrated in 2D devices. Also 3D array scheme is discussed for the high-density NCs scalable for photodetector application.

Effect of illumination on the electron transport mechanisms in Silicon nanocrystal-based nanopixels

In this paper, we present an analysis of conduction in silicon nanocrystals (nc-Si) of small area nanopixels in dark conditions and under illumination. The photosensitive layer of the analyzed devices is mad up a small number of (nc-Si) embedded in SiO2. The interface between the oxide and the silicon substrate is shown to play a significant role in the conduction process: we observed that the presence of (nc-Si) situated inside the oxide, at some angstroms from the interface with the active region, induced discrete variations in the current. In dark conditions the transport of electrons is dominated by trap-assisted mechanisms (Poole-Frenkel, Hopping) at low electric fields and a Fowler-Nordheim mechanism at high electric fields. Under illumination, a new generation-recombination contribution is observed. This mechanism has been carefully studied by Random Telegraph Signal (RTS) measurements. This work shows that the photo-induced current fluctuations (RTS) could be related to the interaction between single photogenerated charges.