Epitaxial Growth and Luminescence Characterization of Si-based Double Heterostructures Light-emitting Diodes with Iron D
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0958-L01-05
Epitaxial Growth and Luminescence Characterization of Si-Based Double Heterostructures Light-Emitting Diodes with Iron Disilicide Active Region Takashi Suemasu1, Cheng Li2, Tsuyoshi Sunohara1, Yuta Ugajin1, Ken'ichi Kobayashi1, Shigemitsu Murase1, and Fumio Hasegawa3 1 Institute of Applied Physics, University of Tsukuba, Ibaraki, 305-8573, Japan 2 Department of Physics, Xiamen University, Xiamen, 361005, China, People's Republic of 3 Kogakuin University, Tokyo, 163-8677, Japan
ABSTRACT We have epitaxially grown Si/β-FeSi2/Si (SFS) structures with β-FeSi2 particles or βFeSi2 continuous films on Si substrates by molecular beam epitaxy (MBE), and observed a 1.6 µm electroluminescence (EL) at room temperature (RT). The EL intensity increases with increasing the number of β-FeSi2 layers. The origin of the luminescence was discussed using time-resolved photoluminescence (PL) measurements. It was found that the luminescence originated from two sources, one with a short decay time (τ~10 ns) and the other with a long decay time (τ~100 ns). The short decay time was due to carrier recombination in β-FeSi2, whereas the long decay time was due presumably to a defect-related D1 line in Si. INTRODUCTION Semiconducting iron disilicide (β-FeSi2) has been attracting significant interest as a Sibased light emitter since the demonstration of EL from β-FeSi2 precipitates embedded in Si pn diodes on Si(001) substrates [1,2]. The emission wavelength of 1.6 µm at RT corresponds to a low loss window of the Si/SiO2 photonic wire waveguide [3,4]. We therefore think that β-FeSi2 is a promising material as a light emitter for optical interconnect in Si integrated circuits. There have been several reports to date on the EL of β-FeSi2 at RT [5-12]. Further efforts have been paid to enhance the luminescence intensity of β-FeSi2 [13,14]. One way to enhance the luminescence intensity of β-FeSi2 is to increase the volume of β-FeSi2 particles in Si without introducing defects. Two- and three-layered β-FeSi2-particles/Si structures with β-FeSi2 size kept constant enhanced the luminescence intensity of β-FeSi2 [10]. Another way is to embed a βFeSi2 continuous film in Si instead of β-FeSi2 particles, and to form Si/β-FeSi2/Si (SFS) double heterostructures (DH). Recently, an SFS DH was realized on Si(111) substrates in spite of the larger lattice mismatch of approximately 5% [15,16], and the EL of β-FeSi2 was also realized at RT [9]. However, there has been no report on the formation of SFS DH on Si(001). This is probably because the epitaxial β-FeSi2 film on Si(001) easily agglomerates into isolated islands when it was annealed or embedded in Si by MBE at high temperatures for improving the crystallinity of β-FeSi2 [17]. As-grown β-FeSi2 films usually show a large hole concentration of approximately 1018cm-3 and low mobility of several tens of cm2/Vs at RT. High-temperature annealing significantly improves these electrical properties and thereby high-temperature process has been considered to be inevitable for obtaining strong luminescence
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