Electrical transport through array of electrochemically etched silicon nanorods

Abstract

2668 2916 ** These authors contributed equally to this work.Random arrays of oxide-passivated silicon nanorods have been obtained by natural oxidation of electrochemically etched porous silicon in air. The charge transport through these nanorods exhibits intriguing characteristics. The I-V characteristics are non-linear, asymmetric, hysteretic, and exhibit resistive switching. Three different charge transport mechanisms dominate in three different ranges of bias and temperature. At high bias, the Fowler-Nordheim tunneling through the oxide barrier is the dominant conduction mechanism. The Pool-Frenkel emission takes over at moderate bias, while at low bias, trap controlled space-charge-limited conduction is the governing mode of charge transport. The bias voltage for cross-over from one transport mechanism to another is sensitively dependent on temperaturethe increase of temperature lowers the cross-over voltage. The observed phenomena can be explained in the framework of lateral transport through a disordered assembly of interconnected semiconducting nanorods. Such multiple transport mechanisms along with tunable cross-over from one mechanism to another simply by changing the bias or temperature, render these nanostructures amenable for a variety of applications. Additionally, the observed resistive switching makes them extremely promising candidates for low power-consuming resistive random access memory devices.

Origin of photo-enhanced hysteretic electrical conductance in nanostructured silicon-based heterojunction

“…Silicon (Si), the building block of microelectronic industries in its nanocrystalline form, became the area of attractive research for the last three decades [1][2][3][4][5]. It is an indirect band gap material in its bulk form but behaves like a direct one when its dimension is reduced to nano-regime due to broadening of uncertainty in k-space leading to relaxation in k-selection rule.…”

“…However, efficiency of electroluminescence from these devices were not high enough for commercial applications. This is mainly due to the growth of a wide band gap non-stoichiometric native silicon oxide layer as a shell material around the nanocrystalline core [3,8,9]. Due to the wider band gap of the oxide shell around the Si nanocrystalline core, stronger confinement of photogenerated carriers favours efficient radiative recombination leading to brighter PL [8,10].…”

“…Whereas, this oxide layer becomes detrimental to electroluminescent and photovoltaic devices by hindering the injection and extraction of charge carriers from nanocrystalline core respectively [6,11]. The exact transport mechanism through SiNCs is still elusive as the nonstoichiometric oxide layer and the oxide related traps play a crucial role during charge transport through it [3,9,[12][13][14]. There are few mechanisms reported in literature revealing the bulk as well as interface/surface states dominated transport process but none of them is conclusive [15][16][17].…”

“…In previously reported studies on charge transport in Si nanostructures, defect/traps states have been found to play a crucial role [3,4,9,26]. Hence, we have tried to explain the transport of charge carriers using a microscopic description of the trapping and detrapping of the photo-excited carriers.…”

“…In the device studied here, the defect/surface states play dominant role in transport, the movement of an injected or photogenerated charge carrier has been considered to have two options. Either the carrier gets trapped in a trap/defect state present in the core-shell interface in Si nanostructure [3,9,26], or it knocks out another trapped charge in its one step movement [4,26]. Hence the transport has been modelled on the basis of trapping and detrapping of charges where the trapping-detrapping resembles to random walk problem adopting Einstein-Smoluchowski's approach [27].…”