Light Emission from Three-Dimensional Silicon-Germanium Nanostructures
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1145-MM02-01
Light Emission from Three-Dimensional Silicon-Germanium Nanostructures D.J. Lockwood1, J.-M. Baribeau1, E-K. Lee2, H-Y. Chang2, and L. Tsybeskov2 1 Institute for Microstructural Sciences, National Research Council Canada, Ottawa, ON K1A 0R6, Canada 2 Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA ABSTRACT Three-dimensional SiGe nanostructures grown on Si using molecular beam epitaxy exhibit photoluminescence (PL) in the important spectral range of 1.3–1.6 µm. At a higher level of photo-excitation, thermal quenching of the PL intensity is suppressed and the previously accepted type II energy band alignment at Si/SiGe cluster hetero-interfaces no longer controls radiative carrier recombination. Instead, a dynamic type I energy band alignment governs the strong decrease in carrier radiative lifetime and further increase in the luminescence quantum efficiency. In contrast to the strongly temperature dependent and slow radiative carrier recombination found in bulk Si, Auger mediated PL emanating from the nanometer-thick Si layers is found to be nearly temperature independent with a radiative lifetime approaching 10-8 s, which is comparable to that found in direct band gap III-V semiconductors. Such nanostructures are thus potentially useful as CMOS compatible light emitters and in optical interconnects. INTRODUCTION Optical interconnects in the form of fiber optics have been used for many years in different long-distance communication applications [1,2]. With the microprocessor clock speed approaching 10 Gbps, optical interconnects are now being considered for board-to-board and onchip technology as an alternative to metal wires with their unavoidable RC delay, significant signal degradation, problems with power dissipation, and electromagnetic interference [2-5]. Two major avenues toward optical interconnects on a chip comprise the hybrid approach with group-III-V optoelectronic components densely packaged into complementary metal-oxide semiconductor (CMOS) architecture [6-9] and the all group-IV (e.g., Si, SiGe, SiGeC, etc.) approach with the all major components, e.g., light emitters, modulators, waveguides and photodetectors, monolithically integrated into the CMOS environment [10]. There have been great efforts over the past several decades to obtain technologically viable and efficient light emission from group-IV materials. In the visible spectral region, the main emphasis has been on porous Si [11-13] and other Si nanostructured systems such as Si/SiO2 superlattices [14-17] and Si nanoprecipitates in SiO2 [18,19]. In the near infrared spectral region, materials and systems such as erbium doped silicon [10,20], Si/Ge quantum wells [21,22], and, more recently, iron disilicide [23] offer potentially useful routes. However, no approach has so far been applied commercially. The reasons for this are: the lack of a genuine or perceived compatibility with conventional CMOS technology; the long carrier radiative lifetime in Si-based nanostructures
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