C. J. Chiu

High-Performance a-IGZO Thin-Film Transistor Using

In this letter, we report the fabrication of an amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor with a high-k dielectric layer on a glass substrate. The room-temperature-deposited a-IGZO channel with Ta2O5 exhibits the following operating characteristics: a threshold voltage of 0.25 V, a drain-source current on/off ratio of 105, a subthreshold gate voltage swing of 0.61 V/decade, and a high field-effect mobility of 61.5 cm2/V·s; these characteristics make it suitable for use as a switching transistor and in low-power applications.

\hbox{Ta}_{2}\hbox{O}_{5}

This study investigates the electrical performance of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with a Ta2O5 gate dielectric under monochromatic illumination. The relationship between the phototransistor performance and oxygen partial pressure is determined. The oxygen content of the a-IGZO channel significantly affects the electrical and optical characteristics of a-IGZO TFTs. At applied gate biases of 0, 0, and 0.25 V, oxygen partial pressures of 0%, 0.1%, and 0.2% yielded measured device responsivities of 0.23, 0.44, and 4.75 A/W, respectively. Oxygen content can be used to control the mobility of TFTs, which can amplify photocurrent and enhance the responsivity of a-IGZO TFTs with a Ta2O5 gate dielectric.

Gate Dielectric

This study investigates the electrical performance of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors with Ga2O3 gate dielectric and applied on deep-ultraviolet phototransistors. To reduce the leakage current, we introduce the SiO2 interlayer dielectric, which effectively reduces the off-current. Under the illumination of 250 nm, the measured responsivity of the device was 3.2 A/W at an applied gate bias of 0 V. The photo-generated carriers were injected into the channel by the applied electric field and Fowler-Nordheim tunneling. A large photocurrent and responsivity can be obtained which is attributed to the high mobility of the a-IGZO channel.

High responsivity of amorphous indium gallium zinc oxide phototransistor with Ta2O5 gate dielectric

The authors report the fabrication of a deep-ultraviolet sensitive a-ZITO thin-film-transistor (TFT) with a Ta₂O₅ gate dielectric. It is found that carrier mobility, threshold voltage, and sub-threshold swing are 106.2 cm²/Vs, 0.75 V, and 0.45 V/decade, respectively, measured in the dark. It is also found that measured current increased from 2.3 × 10^-9 A to 7.97 × 10^-5 A, as we illuminated the sample with λ = 250-nm UV light when V<i>G</i> is biased at 0 V. Furthermore, it is found that deep-UV-to-visible rejection ratio could reach 2.3 × 10⁵ for the fabricated Ta₂O₅/a-ZITO TFT.

Amorphous InGaZnO ultraviolet phototransistors with double-stack Ga2O3/SiO2 dielectric

InGaN/GaN multiquantum-well (MQW) metal-semiconductor-metal photodetectors with a beta-Ga₂O₃ cap layer formed by the furnace oxidation of a GaN epitaxial layer are fabricated and characterized. The beta-Ga₂O₃ cap layer is found to suppress the reverse leakage current by at least about two orders of magnitude with a 5-V applied bias because it creates a thicker and higher potential barrier. The reverse leakage current can be further reduced and a 90-fold larger ultraviolet-to-visible rejection ratio can be achieved by using InGaN/GaN MQW layers, which confine the electron-hole pairs generated by lower-energy photons. In addition, the noise level is reduced and detectivity is increased. With a 5-V applied bias, the noise-equivalent power and normalized detectivity are 8.4 × 10^-13 W and 7.9 × 10¹² Hz^0.5 W^-1, respectively.

Deep UV

β-Ga2O3/AlGaN/GaN heterostructure three-band photodetectors (PDs) are fabricated and operated in ultraviolet (UV)-A, UV-B, and UV-C regions. The operation mode of the device can be switched by changing the applied bias and the thickness of the thin films. The UV-C to UV-B and UV-B to UV-A contrast ratios of the PD with a -1 V applied bias are 14.4 and 2157.9, respectively. The UV-A to visible contrast ratio of the PD with a -10 V applied bias is 247.9.

{\rm Ta}_{2}{\rm O}_{5}

The authors report the fabrication of a deep-ultraviolet (deep-UV) sensitive a-IGZO thin-film-transistor (TFT) with a Ta₂O₅ gate dielectric. It was found that carrier mobility, threshold voltage and subthreshold swing were 48.5 cm²/Vs, 1.25 V and 0.49 V/decade, respectively, when measured in dark. It was also found that measured current increased from 1.5×10^-9 A to 5.56×10^-5 A , as we illuminated the sample with λ = 250 nm UV light when V_G was biased at 0 V. Furthermore, it was found that deep-UV-to-visible rejection ratio could reach 1.0×10⁶ for the fabricated Ta₂O₅/a-IGZO TFT.

/Zinc-Indium-Tin-Oxide Thin Film Photo-Transistor

The authors report the fabrication of Ta2O5 solar-blind photodetectors. It was found that one can transformation amorphous Ta2O5 to crystalline β-Ta2O5 through high-temperature (i.e., >; 700°C) annealing. It was also found that ultraviolet-to-visible rejection ratio of the 900°C-annealed sample was around 9.2 ×102 when biased at 10 V.

InGaN/GaN Multiquantum-Well Metal-Semiconductor-Metal Photodetectors With Beta-

The electrical performance of amorphous indium gallium oxide (a-IGO) thin-film transistors applied as deep-ultraviolet (DUV) phototransistors is investigated. It was found that the bandgap of a-IGO can be engineered by altering its chemical composition. The performance of the phototransistors depended strongly on In2O3 content in the IGO film. When the indium content increases from 21% to 31%, the phototransistor cutoff red-shifted from 280 to 320 nm. The DUV-to-visible rejection ratio and photoresponsivity of the fabricated phototransistors were ~105 and 0.18 A/W.

{\rm Ga}_{2}{\rm O}_{3}

The authors report the growth of TiO₂ nanowires by heating the Ti/glass template and the fabrication of a TiO₂ nanowire metal-insulator-semiconductor (MIS) photodetector (PD). Compared with a TiO₂ nanowire metal-semiconductor- metal PD, it was found that we could achieve a photocurrent 29 times larger. It was also found that the dynamic response of the TiO₂ nanowire MIS PD was stable and reproducible with an on/off current contrast ratio of around 180. With an incident light wavelength of 390 nm and an applied bias of 5 V, it was found that the measured responsivity of the PD was 2.46 × 10^-3 A/W. Furthermore, the noise equivalent power and the detectivity of the fabricated TiO₂ nanowire MIS PD were 7.49 × 10^-12 W and 8.86 × 10¹¹ cm · Hz^0.5 · W^-1, respectively.