Luminescence of black silicon Ali Serpengüzel, 1 Adnan Kurt, 1 Ibrahim Inanç, 2 James E. Cary, 3 and Eric Mazur 4 1 Koç University, Department of Physics, Microphotonics Research Laboratory, Rumelifeneri Yolu, Sariyer, Istanbul 34450 Turkey 2 Sabancı University, Material Science and Engineering Department, Orhanlı, Tuzla, Istanbul 34956 Turkey 3 SiOnyx Inc., 100 Cummings Center, Beverly, Massachusetts 01915 USA 4 Harvard University, Department of Physics and Division of Engineering and Applied Sciences, 29 Oxford Street, Cambridge, Massachusetts 02138 USA aserpenguzel@ku.edu.tr Abstract. Room temperature visible and near-infrared photoluminescence from black silicon has been observed. The black silicon is manufactured by shining femtosecond laser pulses on silicon wafers in air, which were later annealed in vacuum. The photoluminescence is quenched above 120 K due to thermalization and competing nonradiative recombination of the carriers. The photoluminescence intensity at 10K depends sublinearly on the excitation laser intensity confirming band tail recombination at the defect sites. Keywords: band tail recombination, black silicon, laser spectroscopy, luminescence, optical communication, photoluminescence, quenching, recombination, silicon photonics. 1 INTRODUCTION Silicon is the most widely available semiconducting material, since it is the second most abundant material on earth after oxygen. Silicon has been the material of choice for the microelectronics industry for more than half-a-century [1] since it is a relatively inexpensive, and well understood material for producing microelectronic devices [2]. Silicon based electro- photonic integrated circuit (EPIC), i.e., optoelectronic IC (OEIC) [3] is the natural evolution of the microelectronic IC with the added benefit of photonic capabilities. Although silicon photonics is less well developed as compared to the direct bandgap III-V semiconductor photonics; silicon is poised to make a serious impact on the optical communications [4]. Silicon, with a near-infrared indirect bandgap of 1.1 eV is transparent in the optical communication wavelengths greater than 1.1 µm, and is a suitable high refractive index optoelectronic group IV material. Therefore, silicon photonics [5] is experiencing a rapid growth, [6] which is in part driven by the need for low cost photonic devices [7] and the need for high speed intrachip communication [8,9]. Recent progress in silicon photonics is being heralded by the observation of first the Raman gain [10,11] then stimulated Raman scattering (SRS) [12] in a crystalline silicon waveguide, SRS “lasing” first in pulse [13,14] modulated [15] and later in CW [16] silicon Raman “lasers,” and finally the hybrid silicon Raman “laser” [17]. Additionally, silicon modulators [18,19] have been developed first using a metal-oxide-semiconductor (MOS) capacitor [20], a Mach-Zehnder [21] configuration, SRS [22], and a microring [23] configuration. Recently, a silicon microring based wavelength converter has been realized [24]. Racetracks [25], microrings [26], waveguides with feedback [27, 28], and microspheres [29] are some of the resonator geometries pursued for silicon lightwave circuits (SLC's). With well established CMOS processing techniques, it will be possible to integrate lasers, waveguides, modulators, switches, wavelength converters, and photodetectors into silicon motherboards [30] for long haul, metro, local area, interchip, and even intrachip optical communication applications [31]. Journal of Nanophotonics, Vol. 2, 021770 (21 February 2008) ©2008 Society of Photo-Optical Instrumentation Engineers [DOI: 10.1117/1.2896069] Received 15 Jul 2007; accepted 20 Feb 2008; published 21 Feb 2008 [CCC: 19342608/2008/$25.00] Journal of Nanophotonics, Vol. 2, 021770 (2008) Page 1