SIGE QUANTUM-WELLS ON (110)SI GROWN BY MOLECULAR-BEAM EPITAXY

SiGe quantum wells are grown pseudomorphically onto (110) Si substrate s and the layers are characterized by photoluminescence. The optical q uality of the samples is comparable to layers grown onto Si(001). It h as been found that in our molecular beam epitaxy chamber the growth te mperature for fabricating (110) quantum wells with strong excitonic lu minescence is about 785 degrees C, which is roughly 65 degrees C highe r than the temperature needed to obtain optimized SiGe quantum wells o n Si(001). A pronounced red shift of the luminescence energies of the SiGe related signals is observed when compared to quantum wells on (00 1) surfaces. A reduction of the heterostructure bandgap of 23 meV is e stimated 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 ob served when increasing the well width.