Enhanced relaxation of SiGe layers by He implantation supported by in situ ultrasonic treatments

Helium implantation-enhanced strain relaxation of SiGe layers grown pseudomorphically on Si substrates is an interesting alternative for the creation of strained Si CMOS structures. Here we demonstrate the application of additional in situ ultrasonic treatment (UST) during He ion implantation for the formation of relaxed Si0.8Ge0.2 buffer layers. By Raman spectroscopy and X-ray diffraction we show increased relaxation of the SiGe layers under the influence of UST. A rectangular dislocation network with a high dislocation density of about 109-1010 cm−2 concentrated near the interface between the SiGe layer and the Si substrate is shown by TEM for 100 nm SiGe/Si heterostructures after heat treatment at 750 °C, 60 s. Application of ultrasonic waves during He implantation keeps a low surface roughness of about 0.5 nm.