Self-heating effects on strained Si/SiGe n-HFETs

We report an investigation on self heating effects on SiGe based HFET for the first time. Si/SiGe n-HFETs exhibit excellent high frequency performance with f/sub T/ of 90 GHz (105 GHz), f/sub MAX/ of 188 GHz (225 GHz) at 300 K (50 K), low noise figure NF/sub MIN/ of 0.3 dB at 2.5GHz at 300 K. These figures of merit reflect the superior transport properties of the SiGe based heterosystem as compared with bulk Si devices. However some detrimental effects such as parasitic resistances or electrostatic parasitic capacitances as well as self heating effects can mask their strained enhanced intrinsic transport properties. In this communication the last point is addressed through experimental data and 2-D numeric simulations results. Self-heating influence on device performance is pointed out and alternatives to overwhelm them are presented in terms of a device performance comparison between SiGe HFETs prepared on thin and thick virtual substrates (VS).