Si/Si1-xGex photodetectors using three-dimensional growth modes to enhancephotoresponse at lambda=1550 nm

This article explores the use of Si1-xGex quantum-well layers with a cohere nt-wave or island-growth morphology in Si1-xGex based telecommunications ph otodetectors, The structural properties of such heterostructures have been determined by transmission electron microscopy, atomic force microscopy, x- ray diffraction, and Raman scattering. Photoluminescence and photocurrent s pectroscopy measurements establish that strained, dislocation free Si0.5Ge0 .5/Si superlattices were produced with band gaps as low as 0.745 eV, corres ponding to an absorption edge near lambda = 1650 nm. These anomalously low band gaps result from a combination of reduced quantum confinement and high er local Ge concentration at the quantum-well thickness maxims. Waveguide p hotodetectors based on a coherent-wave Si/Si0.50Ge0.50 superlattice have ac hieved a photoresponse of 0.16 A/W at 1550 nm. (C) 2000 American Vacuum Soc iety. [S0734-2101(00)06202-3].