Engineers and scientists are increasingly looking to materials engineering or bandgap engineering as an additional method to deliver increased device performance or new functionality as group IV epitaxy has gained acceptance in CMOS platforms. Heterojunction Tunnel Transistor (HETT) resembles a conventional planar Si n-MOSFET geometry, except that the source contact is replaced by a heavily-doped p-type SiGe region. This device design has the advantage over other tunneling FET designs that it utilizes doped epitaxy to form the source injection contact, and maximizes gate control of the tunneling current by positioning the injection contact directly underneath the gate dielectric. Pure germanium epitaxy is attracting increased attention for a broad range of applications for bandgap engineering. Once a feasible Ge on Si process is developed, it can serve as a platform to enable the growth of III-V materials. This enables a wide variety opportunities to extend silicon devices and circuits via the integration of high performance III-V elements.
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We gratefully acknowledge support from Mike Fritze and DARPA (AFRL contract FA8650-08-C-7806).