Limits...
High Electron Mobility Thin ‐ Film Transistors Based on Solution ‐ Processed Semiconducting Metal Oxide Heterojunctions and Quasi ‐ Superlattices

View Article: PubMed Central - PubMed

ABSTRACT

High mobility thin‐film transistor technologies that can be implemented using simple and inexpensive fabrication methods are in great demand because of their applicability in a wide range of emerging optoelectronics. Here, a novel concept of thin‐film transistors is reported that exploits the enhanced electron transport properties of low‐dimensional polycrystalline heterojunctions and quasi‐superlattices (QSLs) consisting of alternating layers of In2O3, Ga2O3, and ZnO grown by sequential spin casting of different precursors in air at low temperatures (180–200 °C). Optimized prototype QSL transistors exhibit band‐like transport with electron mobilities approximately a tenfold greater (25–45 cm2 V−1 s−1) than single oxide devices (typically 2–5 cm2 V−1 s−1). Based on temperature‐dependent electron transport and capacitance‐voltage measurements, it is argued that the enhanced performance arises from the presence of quasi 2D electron gas‐like systems formed at the carefully engineered oxide heterointerfaces. The QSL transistor concept proposed here can in principle extend to a range of other oxide material systems and deposition methods (sputtering, atomic layer deposition, spray pyrolysis, roll‐to‐roll, etc.) and can be seen as an extremely promising technology for application in next‐generation large area optoelectronics such as ultrahigh definition optical displays and large‐area microelectronics where high performance is a key requirement.

No MeSH data available.


Low operating voltage transistors based on metal oxide quasi‐superlattices. a) Representative sets of transfer characteristics measured from transistors based on QSL‐I and QSL‐III channels. b) Histogram plots of the saturation mobility (μSAT) calculated for a number of low‐voltage QSL‐I‐ and QSL‐III‐based transistors fabricated on the same substrates. The Gaussian fitting curves are guides to the eye.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5016782&req=5

advs201500058-fig-0007: Low operating voltage transistors based on metal oxide quasi‐superlattices. a) Representative sets of transfer characteristics measured from transistors based on QSL‐I and QSL‐III channels. b) Histogram plots of the saturation mobility (μSAT) calculated for a number of low‐voltage QSL‐I‐ and QSL‐III‐based transistors fabricated on the same substrates. The Gaussian fitting curves are guides to the eye.

Mentions: The ability to grow ultrathin layers of oxide dielectrics (e.g., ZrO2) and semiconducting QSLs at low temperatures enables the creation of transistors with state‐of‐the‐art electron mobility values and low‐voltage operation on arbitrary substrates. To further demonstrate the opportunities that the QSL transistor technology has to offer, we fabricated bottom‐gate, top‐­contact transistors on glass and plastic substrates employing the AlOX/ZrO2 as the gate dielectric (see Experimental Section). The bottom‐gate‐staggered device geometry used was similar to that used for transistors made on Si/SiO2 with only exceptions being the gate electrode and gate dielectric materials employed. Because of the thin (≈25 nm) and high‐k (≈9) nature of the bilayer AlOX/ZrO2 gate dielectric (Ci ≈235 nF cm−2),31 ­as‐prepared QSL‐I/III transistors operate at significantly reduced voltages (Figure7a). QSL‐I transistors are found to exhibit consistently slightly lower mobility than QSL‐III devices with a mean value (μSAT(mean)) of ≈37 cm2 V−1 s−1 as compared to the record value of ≈40 cm2 V−1 s−1 for QSL‐III devices (Figure 7b). We note that both mobility values are higher than those obtained for SiO2‐based transistors (Figure 5c). This ­difference is most likely attributed to improved microstructure of the semiconducting layers due to the epitaxial‐like growth on the top of the polycrystalline dielectric.31, 47, 62, 63, 64 The low operating voltage transistors also exhibit respectable on/off current ratios (≈104) and mean subthreshold swings (SS = dVG/d[log(ID)]) of ≈275 mV dec−1 and ≈160 mV dec−1 for QSL‐I and QSL‐III devices (Figure S18, Supporting Information), respectively.


High Electron Mobility Thin ‐ Film Transistors Based on Solution ‐ Processed Semiconducting Metal Oxide Heterojunctions and Quasi ‐ Superlattices
Low operating voltage transistors based on metal oxide quasi‐superlattices. a) Representative sets of transfer characteristics measured from transistors based on QSL‐I and QSL‐III channels. b) Histogram plots of the saturation mobility (μSAT) calculated for a number of low‐voltage QSL‐I‐ and QSL‐III‐based transistors fabricated on the same substrates. The Gaussian fitting curves are guides to the eye.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016782&req=5

advs201500058-fig-0007: Low operating voltage transistors based on metal oxide quasi‐superlattices. a) Representative sets of transfer characteristics measured from transistors based on QSL‐I and QSL‐III channels. b) Histogram plots of the saturation mobility (μSAT) calculated for a number of low‐voltage QSL‐I‐ and QSL‐III‐based transistors fabricated on the same substrates. The Gaussian fitting curves are guides to the eye.
Mentions: The ability to grow ultrathin layers of oxide dielectrics (e.g., ZrO2) and semiconducting QSLs at low temperatures enables the creation of transistors with state‐of‐the‐art electron mobility values and low‐voltage operation on arbitrary substrates. To further demonstrate the opportunities that the QSL transistor technology has to offer, we fabricated bottom‐gate, top‐­contact transistors on glass and plastic substrates employing the AlOX/ZrO2 as the gate dielectric (see Experimental Section). The bottom‐gate‐staggered device geometry used was similar to that used for transistors made on Si/SiO2 with only exceptions being the gate electrode and gate dielectric materials employed. Because of the thin (≈25 nm) and high‐k (≈9) nature of the bilayer AlOX/ZrO2 gate dielectric (Ci ≈235 nF cm−2),31 ­as‐prepared QSL‐I/III transistors operate at significantly reduced voltages (Figure7a). QSL‐I transistors are found to exhibit consistently slightly lower mobility than QSL‐III devices with a mean value (μSAT(mean)) of ≈37 cm2 V−1 s−1 as compared to the record value of ≈40 cm2 V−1 s−1 for QSL‐III devices (Figure 7b). We note that both mobility values are higher than those obtained for SiO2‐based transistors (Figure 5c). This ­difference is most likely attributed to improved microstructure of the semiconducting layers due to the epitaxial‐like growth on the top of the polycrystalline dielectric.31, 47, 62, 63, 64 The low operating voltage transistors also exhibit respectable on/off current ratios (≈104) and mean subthreshold swings (SS = dVG/d[log(ID)]) of ≈275 mV dec−1 and ≈160 mV dec−1 for QSL‐I and QSL‐III devices (Figure S18, Supporting Information), respectively.

View Article: PubMed Central - PubMed

ABSTRACT

High mobility thin‐film transistor technologies that can be implemented using simple and inexpensive fabrication methods are in great demand because of their applicability in a wide range of emerging optoelectronics. Here, a novel concept of thin‐film transistors is reported that exploits the enhanced electron transport properties of low‐dimensional polycrystalline heterojunctions and quasi‐superlattices (QSLs) consisting of alternating layers of In2O3, Ga2O3, and ZnO grown by sequential spin casting of different precursors in air at low temperatures (180–200 °C). Optimized prototype QSL transistors exhibit band‐like transport with electron mobilities approximately a tenfold greater (25–45 cm2 V−1 s−1) than single oxide devices (typically 2–5 cm2 V−1 s−1). Based on temperature‐dependent electron transport and capacitance‐voltage measurements, it is argued that the enhanced performance arises from the presence of quasi 2D electron gas‐like systems formed at the carefully engineered oxide heterointerfaces. The QSL transistor concept proposed here can in principle extend to a range of other oxide material systems and deposition methods (sputtering, atomic layer deposition, spray pyrolysis, roll‐to‐roll, etc.) and can be seen as an extremely promising technology for application in next‐generation large area optoelectronics such as ultrahigh definition optical displays and large‐area microelectronics where high performance is a key requirement.

No MeSH data available.