Si Nanocrystal SiOx Based Light Emitting Diodes and Amplifiers

Abstract
Plasma power controlled PECVD growth of SiOx under SiH4/N2O gas mixture with manipulated Si quantum dot (Si-QD) size for tailoring photoluminescent (PL) wavelength is demonstrated. The incomplete decomposition of N2O at high plasma power facilitates the Si-rich SiOx deposition to enlarge O/Si composition ratio and to shrink Si-QD size. As RF plasma power increases from 20 to 70 W, the O/Si ratio is increased from 1 to 1.6 and the average Si-QD size is reduced from 4.5 to 1.7 nm, which increases Si-QD density from 3.2×1017 to 3.0×1018 cm-3 and blue-shifts PL wavelength from 780 to 380 nm. The multi-color metal-oxide-semiconductor lighting emitting diodes (MOSLEDs) made on Si-rich SiOx are demonstrated. For the red-, green- and blue-color MOSLEDs, the turn-on voltages are 70, 90 and 99 V and their maximum electroluminescence (EL) power are 2.3, 8.6 and 18.2 W/cm2, respectively. The maximum power-current slope and power conversion ratio are determined as 54 mW/A and 2.5×10-4. In addition, the amplification of 785-nm laser signal and saturated small-signal gain of Si QDs embedded in SiO2/SiOx/SiO2 strip-loaded waveguide amplifier made on Quartz and Si is demonstrated. The waveguide with buried Si QDs is optically pumped to provide amplified spontaneous emission centered at 805 nm with a spectral linewidth of 140 nm. By top-pumping the 350 nm-thick SiOx with He-Cd laser of 40 mW at 325 nm, the optical gain of 65 cm-1 and loss coefficient of 5 cm-1 are determined. Under a 785-nm small-signal injection diagnosis, the power-dependent gain curve fitting with gain-saturated amplifier model reveals a peak gain of 27 dB (not including waveguide loss) and a net power gain of 9.6 dB for the Si-rich SiOx waveguide amplifier.