&[mu]-Watt Enhanced Electroluminescent Power of Silicon Nanocrystal Light-Emitting Diodes Made on Nano-Scale Silicon
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0989-A10-05
µ-Watt Enhanced Electroluminescent Power of Silicon Nanocrystal Light-Emitting Diodes Made on Nano-Scale Silicon-Tip-Array Substrate Gong-Ru Lin1, and Chun-Jung Lin2 1 Graduate Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, No. 1, Roosevelt Road, Sec. 4, Taipei, 106, Taiwan 2 Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, No. 1001, Ta Hsueh Road, Hsinchu, 300, Taiwan ABSTRACT A Si nanocrystal based metal-oxide-semiconductor light-emitting diode (MOSLED) on Si nanopillar array is preliminarily demonstrated. Rapid self-aggregation of Ni nanodots on Si substrate covered with a thin SiO2 buffered layer is employed as the etching mask for obtaining Si nanopillar array. Dense Ni nanodots with size and density of 30 nm and 2.8◊1010 cm−2, respectively, can be formatted after rapid thermal annealing at 850∞C for 22 s. The nano-roughened Si surface contributes to both the relaxation of total-internal reflection at device-air interface and the Fowler-Nordheim tunneling enhanced turn-on characteristics, providing the MOSLED a maximum optical power of 0.7 µW obtained at biased current of 375 µA. The optical intensity, turn-on current, maximum power slope and external quantum efficiency of the MOSLED are 140 µW/cm2, 5 µA, 2±0.8 mW/A and 1×10-3, respectively, which is almost one order of magnitude larger than that of a same device made on smooth Si substrate. INTRODUCTION Silicon nanocrystal (nc-Si) based metal-oxide-semiconductor light emitting diodes (MOSLEDs) represent potential candidates for the next generation of optoelectronic applications such as optical interconnect and optical communication. [1-6] The advantages of nc-Si based MOSLEDs include full-color emission, complementary metal oxide semiconductor compatibility, system feasibility, and low cost of fabrication. Electroluminescence (EL) from nc-Si in Si-rich SiO2 (SiOx) film grown by plasma enhanced chemical vapor deposition (PECVD) has previously been observed, [6] however, the EL intensity and external quantum efficiency is still very low since the nature of indirect recombination, the insulating property of the host oxide, and the tunneling dependent carrier injection. Several methods were used to improve the efficiency of carrier injection into nc-Si including the increasing the density of nc-Si embedded in the SiOx film, the decreasing thickness of nc-Si layer and the engineering of the tunneling barrier between contact metal and oxide. However, an approach to improve the carrier injection into nc-Si via Si nano-pillars has never reported. Typically, the fabrication of Si nanopillars mainly relies on the electron-beam (E-beam) lithography and inductively couple-plasma reactive ion etching (ICP-RIE) process. [7] The
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