Novel Field-Effect Schottky Barrier Transistors Based on Graphene-MoS2 Heterojunctions

Abstract

Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5–20 cm2/V·s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 105) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm2/V·s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

Electrolytic phototransistor based on graphene-MoS2 van der Waals p-n heterojunction with tunable photoresponse

“…Nevertheless, such small subthreshold slope is typically one order of magnitude smaller than the value obtained with the conventional back gating method 2 . We observe that the shape of the I-V curve (drain current as a function of drain source bias) is strongly dependent on the gate bias 19 .…”

“…The dependence of the current with respect to irradiance is also linear (inset of Figure 1(d)). As the spot area of the laser is 1 mm 2 and the size of our MoS 2 of about 1400 μm 2 we can therefore estimate a minimum value of the responsivity R of our p-n heterojunction using the formula R = I PC /P light where I PC is the photogenerated current and P light is the incident light on the active photosensor. In our case we obtain responsivity as high as 14 mA/W 13,19 .…”

“…Two-dimensional (2D) materials such as graphene and transition-metal dichalcogendides(TMDC) MX 2 have great potential in next-generation nano-electronic [1][2][3][4] and nano-photonic applications [5][6][7][8][9][10] owing to their extraordinary fundamental physical properties 11 .For example, the field-effect transistors based on monolayer or few-layer MoS 2 have been reported to exhibit an excellent on/off ratio and room-temperature mobility 12 .The layered TMDCbased photodetectors can achieve high responsivity and fast photoresponse 9,13 . The recent studies of growth concerning various 2D materials [14][15][16][17] has opened the possibility to design van der Waals (vdW) heterostructures using graphene as an underlayer, which provides more opportunities for achieving desired electronic or optoelectronic properties 3,[18][19][20][21][22][23][24] .…”

Inhomogeneity in barrier height at graphene/Si (GaAs) Schottky junctions

“…junction, the graphene variant offers the unique advantage of a tunable Fermi level [3][4][5] , and thus Schottky barrier height (SBH) 5,6 , which enables novel device applications such as three terminal transistors with up to 10 6 on/off ratio 5,7 and tunable reverse biased sensors 8 .…”

“…Large variations in SBH, however, have been reported 2,6,9,12 . For example, SBH between 0.25 and 0.92 eV has been observed for Gr/Si Schottky junction 2,6,9,12 .…”