Transparent Zinc Oxide Gate Metal–Oxide–Semiconductor Field-Effect Transistor for High-Responsivity Photodetector

Abstract

Abstract-We report a new structure of high-responsivity photodetectors that utilizes the transparent and metallic zinc oxide (ZnO) gate in bulk silicon metal-oxide-semiconductor field-effecttransistor photodetectors. The device has a small optical window only in the channel region, and all other regions (depletion) are protected from external light. Whereas the amplification of photocurrent by external light was not significant at the floated or positively biased substrate, the photocurrent was enhanced at the grounded or negatively biased substrate due to the decrement of the recombination rate in the n-channel MOSFET. Responsivity was in excess of 1500 A/W under white-light illumination, which is higher than that of conventional photodetectors with the semitransparent polycrystalline-silicon gate.Index Terms-Field-effect phototransistor, photodetector, transparent gate.

Solution-processed dye-sensitized ZnO phototransistors with extremely high photoresponsivity

“…According to the gradual channel approximation model, the threshold voltage of the transistor is directly proportional to the surface charge density and will hence be shifted accordingly, in excellent agreement with the current observation. One important feature in our devices is that they can still be turned off and hence retain high on/off channel current ratio unlike previously reported phototransistors [22][23][24][25][26][27][28][29]35,36 which showed significantly increased channel off-current due to photogenerated holes and electrons.…”

“…This is an extremely high photoresponsivity, being an order of magnitude higher than values reported previously for any other types of phototransistors. [35][36][37][38] It might be argued that if we were to convert the photoresponsivity into the external quantum efficiency (EQE), then the high R value would mean that EQE ) 100%. We speculate that the gain mechanism primarily arises from the extreme sensitivity of the carrier transport at the dielectric/ZnO interface, which improves upon illumination as manifested in the increasing electron mobility with increasing incident light intensity (see Figure 4(a)).…”

Photo sensing analysis of T-shape TFET sensor under visible range of spectrum

“…It is due to the fact that T-shape TFET sensor provides larger vertical tunneling, which further provide excess modulation in drain current under optical operation. Further, analysis states that sensitivity increases in case of ZnO gate whose transmittance of light over 80% [20] in the whole visible range of spectrum, whereas, the polycrystalline-silicon gate oxide absorbs a limited portion of incident photons.…”

“…Furthermore, the channel region is intrinsically doped with concentration of 10 15 cm −3 , whereas, the drain region is heavily doped N + with concentration of 10 18 cm −3 . The Si channel is used and ZnO is act as gate oxide [19,20]. The light is incident over the metal/gate oxide region is shown in figure 1 and the photon is incident over the oxide material to modulate the channel conductivity of T-TFET.…”

Effects of Substrate Temperature on the Electrical and the Optical Properties of N-Type ZnO/P-Type 4H-SiC

“…Among the wide band gap semiconductor materials that have drawn a lot of attention recently, ZnO and SiC are seriously considered as materials for emerging electronics applications. ZnO films have received attention for its application to UV light-emitters, transparent high power electronics, sensor, piezoelectric transducers, and solar cells, because of its high chemical stability, non-toxicity, low cost and high optical band gap of 3.37 eV [6]. In addition, its useful properties include the availability of large area substrate, and a high electron saturation velocity.…”