A homojunction-structured amorphous indium gallium zinc oxide (a-IGZO) phototransistor that can detect visible light is reported. The key element of this technology is an absorption layer composed of hydrogen-doped a-IGZO. This absorption layer is fabricated by simple hydrogen plasma doping, and subgap states are induced by increasing the amount of hydrogen impurities. These subgap states, which lead to a higher number of photoexcited carriers and aggravate the instability under negative bias illumination stress, enabled the detection of a wide range of visible light (400-700 nm). The optimal condition of the hydrogen-doped absorption layer (HAL) is fabricated at a hydrogen partial pressure ratio of 2%. As a result, the optimized a-IGZO phototransistor with the HAL exhibits a high photoresponsivity of 1932.6 A/W, a photosensitivity of 3.85 × 10, and a detectivity of 6.93 × 10 Jones under 635 nm light illumination.
We present a solution-processed
oxide absorption layer (SAL) for detecting visible light of long wavelengths
(635 and 532 nm) for indium–gallium–zinc oxide (IGZO)
phototransistors. The SALs were deposited onto sputtered IGZO using
precursor solutions composed of IGZO, which have the same atomic configuration
as that of the channel layer, resulting in superior interface characteristics.
We artificially generated subgap states in the SAL using a low annealing
temperature (200 °C), minimizing the degradation of the electrical
characteristics of thin-film transistor. These subgap states improved
the photoelectron generation in SALs under visible light of long wavelength
despite the wide band gap of IGZO (∼3.7 eV). As a result, IGZO
phototransistors with SALs have both high optical transparency and
superior optoelectronic characteristics such as a high photoresponsivity
of 206 A/W and photosensitivity of ∼106 under the
influence of a green (532 nm) laser. Furthermore, endurance tests
proved that the IGZO phototransistor with SALs can operate stably
under red laser illumination switched on and off at 0.05 Hz for 7200
s.
We proposed a simple method, a thermally purified solution (TPS) process, to lower the fabrication temperature of solution-processed hafnium oxide (HfOx) gate insulator films.
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