Si Nano-Dots and Nano-Pyramids Dependent Light Emission and Charge Accumulation in ITO/SiO $_{\rm x}$ /p-Si MOS Diode

The current blocking and charge accumulation effects of an ITO/Si-rich SiO_x/p-Si MOS diode with buried Si nano-dots and SiO_x/Si interfacial Si nano-pyramids are characterized. The ITO/Si-rich SiO_x/p-Si MOS diodes exhibits the 3.5 ± 0.2 nm large Si nano-dots with volume density of 4-5×10¹⁸ cm^-3. At the SiO_x/p-Si interface, the area density of Si nano-pyramids is increasing from 1.3×10⁹ to 1.6×10¹¹ cm^-2, which greatly decreases turn-on voltage of the MOS diode from 182 to 52 V, thus enhancing the electro-luminescent power from 17.5 to 50.4 nW. The current blocking phenomenon of such a MOS diode become serious with lengthening step-voltage delay, indicating that a significant charge accumulation associated with a strong screening field is generated within Si-rich SiO_x layer. It was observed that the turn-on voltage with Si nano-pyramids evidently decreases to 31.6 V under reverse biased conditions for tunneling holes. Counter-clockwise C-V hysteresis analysis reveals a flat-band voltage shift of 8.5 V for electron and -12.9 V for hole, showing nonlinear function with either Si nano-dot volume or density. The C-t retention shows higher charge loss rate for electrons (7.6%) than for holes (1.5%) within 0.5 hr due to low SiO_x/Si nano-dot barrier.