THERMAL-STABILITY OF UNDOPED STRAINED SI CHANNEL SIGE HETEROSTRUCTURES

We have investigated the thermal stability of Si/SiGe n-channel hetero structures. 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 concentratio n in the strained Si channel is controlled from a back gate. Our devic es show high electron mobility of up to 19 500 cm(2)/V s at 77 K and a re stable with negligible 77 K mobility reduction after anneals at 800 degrees C for 30 min and at 950 degrees C for 3 min. These results co nform well with a simulation of the diffusion of Ge into the Si channe l. (C) 1996 American Institute of Physics.