Graphene Klein tunnel transistors for high speed analog RF applications

• Published in: Scientific reports Vol. 7; no. 1; pp. 9714 - 9
• Main Authors: Tan, Yaohua, Elahi, Mirza M., Tsao, Han-Yu, Habib, K. M. Masum, Barker, N. Scott, Ghosh, Avik W.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29-08-2017; Nature Publishing Group
• Subjects: 119/118; 639/301/357/918/1052; 639/925/918/1052; Humanities and Social Sciences; multidisciplinary; Radio frequency; Science; Science (multidisciplinary); Transistors
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-10248-7

We propose Graphene Klein tunnel transistors (GKTFET) as a way to enforce current saturation while maintaining large mobility for high speed radio frequency (RF) applications. The GKTFET consists of a sequence of angled graphene p-n junctions (GPNJs). Klein tunneling creates a collimation of electrons across each GPNJ, so that the lack of substantial overlap between transmission lobes across successive junctions creates a gate-tunable transport gap without significantly compromising the on-current. Electron scattering at the device edge tends to bleed parasitic states into the gap, but the resulting pseudogap is still sufficient to create a saturated output (
I
D
–
V
D
) characteristic and a high output resistance. The modulated density of states generates a higher transconductance (
g
m
) and unity current gain cut-off frequency (
f
T
) than GFETs. More significantly the high output resistance makes the unity power gain cut-off frequency (
f
max
) of GKTFETs considerably larger than GFETs, making analog GKTFET potentially useful for RF electronics. Our estimation shows the
f
T
/f
max
of a GKTFET with 1
μ
m channel reaches 33 GHz/17 GHz, and scale up to 350 GHz/53 GHz for 100 nm channel (assuming a single, scalable trapezoidal gate). The
f
max
of a GKTFET is 10 times higher than a GFET with the same channel length.