Normal-incidence SiGe/Si photodetectors with different buffer layers

Abstract

Normal-incidence SiGe/Si p–i–n photodetectors with relaxed GeSi alloy layers grown on Si buffer layers at low temperature and fraction-graded Si1−xGex buffers were fabricated by rapid thermal process/very-low-pressure chemical-vapor deposition. The response wavelength of these detectors ranges from 0.7 to 1.55 μm. The peak wavelengths are 0.98 and 1.06 μm, at which the responsivities are 2.7 and 1.8 A/W (−2 V), respectively. The responsivities at 1.3 μm are 0.15 and 0.07 A/W (−5 V), and the dark current densities are 0.05 and 0.03 μA/mm2 (−2 V), respectively. The influences of the Ge fraction, epilayer thickness, and bias voltage on the detectors are discussed.