Compositional dependence of the absorption edge and dark currents in Ge_(1-x-γ)Si_xSn_γ/Ge(100) photodetectors grown via ultra-low-temperature epitaxy of Ge_4H_(10), Si_4H_(10), and SnD_4

摘要

Lattice-matched Ge_(1-x-y)Si_xSn_y (x≤0.2, y≤0.05) alloys were deposited defect-free on Ge(001) substrates via low-temperature (330-290 ℃) reactions of Ge_4H_(10), Si_4H_(10) and SnD_4 hydrides, and used to fabricate pin photodetectors. The growth is carried out undet-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.