16:15 〜 16:30
▼ [19p-W834-11] Drastic improvement of effective carrier lifetimes in Si nanowires embedded with anodic aluminum oxide by post-deposition anneal
キーワード：nanowires,characterization of nano-material properties,characterization methods
We report on drastic increase of effective carrier lifetimes in Si nanowires (Si NW) embedded with anodic aluminum oxide (AAO) by thermal treatment. The Si NW were grown using selective growth technique assisted with AAO template, which offers the vertically epitaxial structures with controlled diameter, good mechanical stability supported by AAO template, availability of cheap passivation material and absence of metallic contamination. Growth conditions were strictly considered to avoid the non-selective deposition of Si grains on AAO template, which prevented the incoming laser from penetrating into Si NW for generating excess carriers inside Si NW. The optimized growth conditions comprising growth temperature of 800 oC, Si2H6 flow rate of 0.5 sccm and a growth time of 90 min were utilized. To reduce the recombination effect on top of Si NW, the as-grown samples were passivated by alumina thin film using thermal atomic layer deposition (ALD). The carrier lifetime measurement was carried out by microwave photo-conductivity decay (μPCD) method employing the wavelength of incident source of 349 nm and 10 GHz. It was found that the effective carrier lifetime increases from 25.2 to 49.6 μs under injection level of 5x1013 cm-2 upon postdeposition anneal of 400 oC. It was turned out that efficiency of thermal treatment of around 400oC can be relevant with satisfactory low interface defect density presumably thanks to field-effect passivation as well as chemical passivation. Furthermore, thermal treatment at 600 oC yielded an increase of effective carrier lifetime of 83.2 μs at the same injection level thanks to possible diffusion of carriers inside Si substrate.