Si- and SiGe-Based LEDs
Single crystal Si, Si0.948Ge0.052 and Si0.66Ge0.34 diodes as well as Ge transistor structures with high electroluminescence (EL) intensities in the region of interband transitions at room temperature were fabricated by different techniques and their luminescence properties were studied. By varying the Ge content in the solid solution, one can control the wavelength at the emission maximum in the range of 1.1 - 1.8 μm. The integrated EL intensity varies by a factor of less than two in the temperature ranges of 80 - 500 and 80 - 300 K for Si and SiGe LEDs, respectively. Si LEDs can effectively operate, at least, up to ~200°C. The data analysis shows that recombination involving excitons is the dominant mechanism of near-band-edge radiative recombination in all the light-emitting structures at room temperature. Some of the structures have record values of EL intensity and/or quantum efficiency, so they can be used as effective light emitters in Si optoelectronics. In particular, Si LEDs were designed with a small p-n junction area of 8x10-3 mm2 and a radiation power of 0.3 mW. The record total emission power of 46 mW was achieved in solar cell LEDs with an emitting surface area of 3 сm2. The internal quantum efficiencies of 0.5% and 0.3% were recorded in Si0.948Ge0.052 and Si0.66Ge0.34 LEDs at the wavelengths of 1.15 and 1.3 μm, respectively. Room temperature near-band-edge EL was first observed in Ge structures.
Bo Monemar, Martin Kittler, Hermann Grimmeiss
N.A. Sobolev "Si- and SiGe-Based LEDs", Materials Science Forum, Vol. 590, pp. 79-100, 2008