Si/SiGe modulation doped field-effect transistor with two electron channels

Si/SiGe modulation doped field-effect transistors with a two-dimensional electron gas in a cap and in a regular channel, 10 nm and 40 nm underneath the gate, were realised. The bias dependent population of the channels is explained by means of the bandstructure. High extrinsic transconductances of 155 mS/mm for the upper channel and 80 mS/mm for the deeper channel were obtained. Significant device improvements due to source/drain contact implantation are demonstrated by comparison with simultaneously processed devices with alloyed contacts.