The influence of ion beam-synthesized InSb nanocrystals on current-voltage characteristics of SiO2 layers in MOS structures

Current density ( J ) as a function of electric field ( E ) at different temperatures ( T ) is studied in Al/SiO 2 <InSb> /Si/Al metal-oxide-semiconductor (MOS) structures fabricated using silicon-on-insulator and ion-beam synthesis technologies. The MOS structures containing SiO 2 layers implanted with Sb + and In + ions are investigated both before and after annealing at 800 and 1100 ℃. Annealing leads to the formation of InSb nanocrystals (5 – 25 nm in diameter) to result in a unique charge distribution within SiO 2 . Three distinct types of J ( E , T ) behavior are observed in the temperature range 2 < T < 300 K and at electric fields up to ±6.7 × 10 5 V/cm. At E < 4 × 10 4 V/cm, all samples exhibit ohmic conduction, whereas at higher fields ( E > 2 ×10 5 V/cm) the J ( E , T ) dependences follow the space charge-limited current (SCLC) models: Below 40 K, the Mott-Gurney law applies, indicating monoenergetic traps near the SiO 2 midgap. Above 40 K, the J ( E , T ) behavior is consistent with the Mark-Helfrich SCLC model, revealing an exponential energy distribution of traps in the “tails” of localized states in SiO 2 . These localized states are associated with an implantation-induced structural disorder. An energy band diagram of the annealed MOS structures has been developed to directly correlate the Fermi-level shifts and the evolution of trap states with the formation of InSb nanocrystals. This correlation provides a benchmark insight into the redistribution of free and localized charges in modified SiO 2 <InSb> layers and explains their influence on the observed J ( E , T ) characteristics. The contribution of this work lies in establishing a direct link between the nanocrystal-induced disorder and the charge redistribution in modified oxide layers subjected to annealing. • InSb nanocrystals in SiO 2 were obtained using SOI and ion-beam synthesis technology. • J - E curves follow two types of space charge-limited current models. • Two types of traps (monoenergetic, exponential) were detected based on J-E analysis. • J - E laws change when Fermi level crosses energy regions of different traps types. • An energy band structure and evolution of DOS diagrams are developed schematically.