Thermal stability of undoped strained Si channel SiGe heterostructures

We have investigated the thermal stability of Si/SiGe n-channel heterostructures. To eliminate the complication of dopant diffusion, we have fabricated undoped Si/SiGe heterostructure Hall effect devices. With no modulation doping used in our structures, the electron concentration in the strained Si channel is controlled from a back gate. Our devices show high electron mobility of up to 19500 cm2/Vs at 77 K and are stable with negligible 77 K mobility reduction after anneals at 800°C for 30 min and at 950°C for 3 min. These results conform well with a simulation of the diffusion of Ge into the Si channel.