Si∕SiGe n-channel modulation-doped field effect transistor on air

Si/SiGe n-channel modulation-doped field effect transistors (MODFETs) have been fabricated on a 10 /spl mu/m-thick membrane by removal of the Si substrate and SiGe virtual substrate under the device layers. The membrane devices, surrounded by air, were characterised after thinning and compared to the unthinned characteristics. A large reduction of the off-currents of the MODFETs on air, due to an increase in substrate resistance, has been measured, making them more suitable for low-power applications.