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Thermoelectric signals from Si/SiGe superlattices

Zhou Xiaofang1,2,3, Jiang Zuimin3, Lin Jianhui3, Tang Xiaodong4, Chen Qingming1, Zhang Hui1 and Zhang Pengxiang1,5

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p-Si/Si0.5Ge0.5 superlattices (SLs) grown on a vicinal-cut p-type silicon single crystalline substrate by molecular beam epitaxy (MBE) were irradiated by a KrF excimer laser. Two types of transient laser induced voltage (LIV) signals were observed, among which the signals of 0.3 V in amplitude with time response ~40 ns showed up along the tilted directions, while voltage signals of ~10 mV with a time response of tens of microseconds presented along the untilted directions which were perpendicular to the tilted direction. The results demonstrate that the observed photoelectric signals of 0.3V amplitude are laser induced thermoelectric voltages (LITV) due to the tilting angle relation. The observed LIV signals implied that these SLs exhibited anisotropic Seebeck components. It was also found that the LIV signals increased with the p-type doping level in the Si layer, which was coincident with the expectation of the laser induced thermoelectric effect. According to the measured signals and the theoretical formula, one can calculate the physical parameters of the SLs. The calculated effective Seebeck anisotropy coefficients (SabSc) for samples with 1018 cm−3 and 1020 cm−3 are approximately 11.2 µV K−1 and 18.2 µV K−1, respectively.


PACS

73.63.-b Electronic transport in nanoscale materials and structures

68.65.Cd Superlattices

81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

72.20.Pa Thermoelectric and thermomagnetic effects

72.40.+w Photoconduction and photovoltaic effects

Subjects

Condensed matter: electrical, magnetic and optical

Semiconductors

Surfaces, interfaces and thin films

Nanoscale science and low-D systems

Dates

Issue 22 (21 November 2009)

Received 27 March 2009, in final form 6 September 2009

Published 27 October 2009



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