Study on electroluminescence from multiply-stacking valency controlled Si quantum dots

• We have fabricated two-tiered heterostructures consisting of δ-doped Si-quantum-dots.
• The PN junction-like Si-quantum-dots stack is effective to realize high efficient EL.
• A simple stacking of B-doped Si-quantum-dots is better suited to low power operation.

We have fabricated two-tiered hetero-structures consisting of B δ-doped and P δ-doped Si quantum dots (QDs) embedded in SiO2 on p- and n-Si(100) by repeating Si-QDs formation by low pressure chemical vapor deposition (LPCVD) using pure SiH4 and subsequent surface oxidation and modification by remote plasma, and characterized their electroluminescence (EL) in near-infrared region under DC and AC bias applications to semitransparent Au top-electrodes. The observed EL spectra can be deconvoluted into mainly two components peaked at ~ 1.07 and ~ 1.11 eV, which involve recombination processes through impurity levels. The input power dependence of EL intensities shows that two-tiered structure of P-doped and B-doped Si-QDs is effective to improve EL efficiency while a simple stacking of B-doped Si-QDs is suited to low power operation. This indicates that energy relaxation to lowest quantized levels in charge transfer among valency controlled Si-QDs by impurity doping plays a role on recombination of injected electrons and holes.