Charge transport and electroluminescence of silicon nanocrystals/SiO2 superlattices

Abstract

Charge transport and electroluminescence mechanisms in Si-rich Si oxynitride/silicon oxide (SRON/SiO2) superlattices deposited on p-type Si substrate are reported. The superlattice structures were deposited by plasma-enhanced chemical-vapor deposition and subsequently annealed at 1150 °C to precipitate and crystallize the Si excess into Si nanocrystals. The dependence of the electrical conduction on the applied voltage and temperature was found to be well described by a Poole-Frenkel transport mechanism over a wide voltage range. On the other hand, the observed dependence of the electroluminescence on the SRON layer thickness is a clear proof of quantum confinement and was attributed to an excitonic radiative recombination taking place in the confined states within the Si quantum dots. A model is proposed based on thermal hopping of electrons between the quantum dots acting as trap states (Poole-Frenkel). A correlation between carrier transport and electroluminescence has been established considering impact ionization of high-kinetic energy electrons on the Si quantum dots

Structural parameters effect on the electrical and electroluminescence properties of silicon nanocrystals/SiO2 superlattices

“…In all samples, the SRON layer thickness, t SRON , was held constant at 3.5 nm, observed in a previous work to be close to the optimum EL performance [20]. The fabricated samples are summarized in table 1.…”

“…The employed top-electrode circular area was ∼2 × 10 −3 cm 2 . Further information on the material deposition and the device processing has been reported in previous works [7,18,20].…”

“…The former effect, attributed to a capacitorrelated displacement current, suggests that charge is being trapped within the material in this regime. Instead, high voltages provide a conduction zone, associated to a PooleFrenkel (bulk-limited) mechanism through NC allowed energy levels, demonstrated in a previous work on similar structures to be the dominant transport mechanism [20].…”

“…across the layers) is commonly ascribed to trapassisted-or tunnel-like mechanisms, depending on the structure parameters and the fabrication technique [17,18]. The electroluminescence (EL) properties of this material structure have also been investigated and correlated to the vertical transport mechanisms [19,20]. However, the influence of the different structural parameters involved in the fabrication of NCs (i.e.…”

Luminescent Devices Based on Silicon-Rich Dielectric Materials

“…Red or near infrared emission has been observed in these structures and has been related to both excitonic recombination taking place in conined states within Si-nps or relaxation of hot electrons [25,26].…”