Compositional dependence of the absorption edge and dark currents in Ge1-x-ySixSny/Ge(100) photodetectors grown via ultra-low-temperature epitaxy of Ge4H10, Si4H10, and SnD4

Lattice-matched Ge1-x-ySixSny (x <= 0.2, y <= 0.05) alloys were deposited defect-free on Ge(001) substrates via low-temperature (330-290 degrees C) reactions of Ge4H10, Si4H10 and SnD4 hydrides, and used to fabricate pin photodetectors. The growth is carried out under gas-source molecular beam epitaxy conditions in a specially designed single-wafer reactor. Optical responsivity measurements reveal absorption edges between 0.88 eV and 0.98 eV, which are used to determine the compositional dependence of the direct band gap. A study of the I-V characteristics of the diodes shows that the dark current is very weakly correlated with the number of Si-Sn bonds in the alloy. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768217]