Ge 1-x C x /Si heterojunction photodiode

Abstract

We report on the fabrication and characterization of a photodiode made from a heterojunction of epitaxial p-type Ge1-xCx on an n-type Si substrate. Epitaxial Ge1-xCx layers with carbon percentages of 0.2, 0.8, 1.4 and 2% were grown on (100) Si substrates by solid source molecular beam epitaxy. The p-GeC/n-Si junction exhibits diode rectification with low reverse saturation current (<EQ 89 pA/micrometers 2 at -1 volt) and high reverse breakdown voltage in excess of -40 volts. Despite the large number of dislocations and defects at the heterojunction, photoresponsivity was observed from the p- Ge1-xCx/n-Si diodes using laser excitation at a wavelength of 1.3 micrometers . External quantum efficiency was measured between 1.2 and 2.3%.