Silicon Nanocrystallite Light Emitting Devices Fabricated by Full Pulsed-Laser-Ablation Process
- PDF / 353,753 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 117 Downloads / 166 Views
Silicon Nanocrystallite Light Emitting Devices Fabricated by Full Pulsed-Laser-Ablation Process Yuka Yamada, Toshiharu Makino, Nobuyasu Suzuki, Takehito Yoshida Advanced Technology Research Laboratories, Matsushita Electric Industrial Co., Ltd., 3-10-1 Higashimita, Tama-ku, Kawasaki 214-8501, Japan
ABSTRACT We have developed silicon (Si) nanocrystallite light-emitting devices synthesized by a novel integrated process in which a size-controlling unit of differential mobility analyzer (DMA) is combined to a nanocrystallite formation unit of pulsed laser ablation (PLA). The size-controlled Si nanocrystallites as active layers have been deposited on Si substrates, and have been covered with stoichiometric indium oxide (In2O3) thin films synthesized also by the PLA process. The electroluminescence (EL) spectra had a narrow bandwidth of 0.15 eV peaked at slightly higher energy region (1.17 eV) than the bulk Si energy gap (1.10 eV), at room temperature.
INTRODUCTION It is well known that group IV elements (Si, Ge) are capable of emitting strong visible light at room temperature when they undergo size reduction to the nanometer region [1]. Recently, various methods of forming nanostructured Si have been studied. However, it has been difficult to develop nanoparticles into advanced functional devices because they have a large percentage of surface-exposed atoms, and are extremely sensitive to impurities and/or damage. Light-emitting properties of the nanoparticles, particularly light-emitting wavelength and efficiency, strongly depend on their mean sizes and size distributions [2]. Therefore, the necessities for the Si nanocrystallite synthesis are formation in clean process without impurities and precise size controllability in less than 5 nm. Furthermore, to develop Si nanocrystallites into light-emitting diodes (LEDs), Si nanocrystallites should be surrounded by wide bandgap materials and electrons should be efficiently injected to Si cores. As wide bandgap surrounding materials of Si nanocrystallte LEDs, transparent conducting oxide films are suitable. However, oxygen (O2) gas introduction and substrate heating are required for oxygen compensation or crystallization when the transparent conducting oxide films are formed by physical vapor deposition method [3,4], which are exclusive with Si nanocrystallites. Pulsed laser processing is cold-walled processing which excites only beam-focused areas, which enables a clean ambient, and is thus highly suitable for nanoparticle synthesis [5]. In particular, pulsed laser ablation in inert background gas (PLA-IBG) is one of the promising methods of synthesizing functional Si nanoparticles [6,7]. Furthermore, the background gas pressure can be varied freely in the PLA process. The transitions of structures of deposited species occur by varying the background gas pressure, from thin films to nanoparticles [8,9]. In this work, we develop full PLA-IBG process, integrated for synthesizing both size-controlled Si nanocrystallites and transparent conducting oxide thin films. Size contro
Data Loading...
