SiGe low loss waveguides for 1.3 μm grown by selective epitaxy

Abstract

The realisation of 2D SiGe-Si strained layer low loss waveguides (1.7 dB/cm) for the 1.3 /spl mu/m wavelength is reported. The waveguide geometry is grown by selective epitaxy. It ensures loose cut-off and critical thickness conditions. Recently, room-temperature operation of vertical emitting SiGe-Si LEDs made by selective epitaxy has been demonstrated and integration with SiGe-Si waveguides and photodetectors open the opportunity towards OEICs. The main design parameter for these devices is the confinement factor in the active SiGe layer. Recent advances in selective epitaxy allowed us to increase the Si/sub 1-x/Ge/sub x/ guiding film thickness by 4 times over the plastic relaxation limit on large areas. Therefore, higher confinement factors could be achieved. The main difference from other methods is the local deposition of the SiGe in a finite stripe region while in the conventional rib or ridge geometry, the SiGe layer is deposited on an entire wafer and then patterned by reactive ion etching. The increased amount of Ge (19%) incorporated in these waveguides, and a reduced Si cap layer are improvements from previous reported SiGe-Si waveguides, where thick Si cap layers and reduced Ge concentrations (<10%) are used.