SiGe quantum wells on (110) Si grown by molecular beam epitaxy

SiGe quantum wells are grown pseudomorphically onto (110) Si substrates and the layers are characterized by photoluminescence. The optical quality of the samples is comparable to layers grown onto Si(001). It has been found that in our molecular beam epitaxy chamber the growth temperature for fabricating (110) quantum wells with strong excitonic luminescence is about 785°C, which is roughly 65°C higher than the temperature needed to obtain optimized SiGe quantum wells on Si(001). A pronounced red shift of the luminescence energies of the SiGe related signals is observed when compared to quantum wells on (001) surfaces. A reduction of the heterostructure bandgap of 23 meV is estimated for a Ge content of 16.5% as evaluated from the luminescence energies of samples with different well widths. The relative intensity of the no-phonon transition with respect to the TO phonon replica is enhanced by about a factor of two for quantum wells grown onto Si(110). A decrease of the integral SiGe related luminescence intensity is observed when increasing the well width.