Self-Align Formation of Si Quantum Dots

Abstract

One-dimensionally aligned Si quantum dots (Si-QDs) on ultrathin SiO2 have been prepared by controlling the selective growth conditions of low-pressure chemical vapor deposition (LPCVD) using pure SiH4 or 5% GeH4 diluted with He, the oxidation of the dots and the selective etching. Atomic force microscopy (AFM) observations and X-ray photoelectron spectroscopy (XPS) measurements confirm the selective etching of Ge oxide on pre-grown Si-QDs by annealing under vacuum condition and the subsequent selective growth of 2nd Si-QDs on the 1st Si-QDs. The temporal change in surface potential of the self-aligned Si-QDs after one electron injection from the tip to the dots changed in a stepwise manner with time due to electron transfer from the 2nd-dot to the 1st-dot. For the semitransparent Au-gate diodes, when carriers were injected to self-aligned Si-QDs from n-Si(100) substrate for electrons and from Au top electrode for holes, electroluminescence (EL) in the near-infrared region at room temperature becomes observable with an increase in the current at positive gate biases over the thresholds. It should be noted that the self-aligned Si-QDs enhance the emission intensity by a factor of ~2 compared with Si-QDs stacked structure under the same current density. This result indicates that self-aligned structure is suitable for an increase in recombination efficiency for EL.