Growth and characterization of Ge1-xSix (x≤10at%) single crystals

GeSi single crystals in the range Si less than or equal to 10 at% have been grown on Ge [1 1 1]-seed crystals by the vertical Bridgman method in a radiation heated mirror furnace. The diameter of the crystals was 9 mm, their length about 30-40 mm. Axial and radial macrosegregation have been measured by energy dispersive analysis by X-ray (EDAX), microsegregation was investigated using interference contrast microscopy. The average EPD is in the range 6 x 10(4)-1 x 10(5) cm(-2) and is enhanced at the seed/crystal interface and in the part grown in the vicinity of the container wall. Measurements with a Bartels five crystal diffractometer of the [1 1 1] peak resulted in FWHM (full-width at half-maximum) values of 20 to 40 arcsec, compared to the theoretical value of 17 arcsec. The FWHM values of the bound excitons, determined by photoluminescence, are in the range 2.5-4.5 meV, which are the best values reported hitherto, and show a linear enlargement with increasing silicon concentration. The segregation coefficients of Ga, In, P, As, and Sb fit well to a linear interpolation between the Ge and Si values. (C) 1998 Elsevier Science B.V. All rights reserved.