Design and Simulation of a Novel Graded-Channel Heterojunction Tunnel FET With High ${I} _{\scriptscriptstyle\text {ON}}/{I} _{\scriptscriptstyle\text {OFF}}$ Ratio and Steep Swing

In this letter, a novel graded-channel heterojunction tunnel field-effect transistor (GCH-TFET) is proposed and studied by simulation. The novel TFET adopts a near broken-gap heterojunction at the source/channel interface to enhance the tunnel efficiency. Besides, it employs a graded component channel which works as an electron barrier to block up the leakage current at the OFF-state and can be removed with the increased gate voltage at the ON-state for high ON/OFF-current (I
_ON
/I
_OFF
) ratio. Such graded channel also allows a sudden turn-on of band-to-band tunneling, resulting in a reduced sub-threshold swing (SS) compared with conventional heterojunction TFETs. The GCH-TFET demonstrates an I
_ON
/I
_OFF
ratio of more than seven decades with I
_ON
up to 225 μA/μm at V
_DD
= 0.3 V, I
_OFF
more than two decades lower than a near broken-gap heterojunction TFET and SS lower than 30 mV/decade for more than five decades, exhibiting excellent potential for ultra-low power applications.