Electrical and optical properties of Ge-implanted 4H-SiC

The structural, electronic, and optical properties of single crystalline n- type 4H-SiC implanted with Ge atoms have been investigated through x-ray di ffraction (XRD), Rutherford backscattering spectroscopy (RBS), Raman spectr oscopy, and sheet resistivity measurements. Ge atoms are implanted under th e conditions of a 300 keV ion beam energy with a dose of 2 x 10(16) cm(-2). X-ray diffraction of the Ge-implanted sample showed broadening of the Brag g peaks. A shoulder on the (0004) reflection indicated an increase in the l attice constant corresponding to substitutional Ge and implantation induced lattice damage, which was repaired through thermal annealing at 1000 degre es C. The diffraction pattern after annealing indicated improved crystal st ructure and a peak shift to a lower reflection angle of 35.2 degrees. The c omposition of Ge detected through XRD was reasonably consistent with RBS me asurements that indicated 1.2% Ge in a 1600-Angstrom-thick layer near the S iC surface. Raman spectroscopy also showed fundamental differences in the s pectra obtained for the Ge-implanted SiC (SiC:Ge) compared to a pure sample of SiC. Sheet resistivity measurements indicate a higher conductivity in t he Ge implant by a factor of 1.94 compared to unimplanted SiC. These result s have demonstrated the possibility of substitutional implantation of Ge at oms into the crystalline lattice of 4H-SiC substrates. The change in compos ition and properties may have numerous electronic device applications inclu ding high power, high temperature, optoelectronic, as well as high frequenc y device structures. (C) 1999 American Institute of Physics. [S0003-6951(99 )02504-8].