OPTIMIZATION OF SI1-XGEX SI WAVE-GUIDE PHOTODETECTORS OPERATING AT LAMBDA=1.3-MU-M/

This paper analyzes the influence of various design parameters in the external quantum efficiency (QE) of waveguide detectors based on Si/Si 1-xGex strained-layer superlattices (SLS's), for use in optical commun ications at lambda = 1.3 mu m. The study presents an algorithm that au tomatically generates structurally stable SLS's. This generation is co mpleted by intensive simulation of the generated SLS's to calculate th e external QE. The simulation embraces optical waveguiding, absorption , quantum size effect, as well as thermodynamics of the strained layer s. Two sets of data were created using two different models for the Si Ge layer critical thickness, h(c)(x). A conservative model for h(c), c orresponding to the equilibrium regime, yielded discrete maximum value s for QE (around 12%) that were mainly dependent on the alloy absorpti on. A second model for h(c), corresponding to the metastable regime, p roduced considerably higher QE's (around 60%), and shows the great imp ortance of fiber-to-waveguide coupling efficiency. The importance of t he passive-waveguide coupler geometry is investigated using the beam p ropagation method.