In this paper, we describe a three-layer-stacked color image sensor comprising two organic photoconductive films (OPFs) with thin-film transistor-based readout circuits and a complementary metal–oxide–semiconductor (CMOS) image sensor. In this three-layer-stacked sensor, a blue-sensitive OPF selectively absorbs blue light, a green-sensitive OPF selectively absorbs green light, and a CMOS image sensor (CIS) receives red light. Color video imaging operation at 60 frames per second was confirmed for a prototype sensor having 320 × 240 pixels with a pixel pitch of 20 μm without a color filter array, and good color separation and a linear response of the sensor were achieved owing to the combination of the CIS and color-selective OPFs.

Amorphous GaN films were deposited using compound source MBE. GaN powder was used as the source material and no additional nitrogen sources were supplied. Although the N/Ga ratio in the layers deposited at temperatures lower than 400 °C was low, an increase of the substrate temperature improved the N/Ga ratio. The emission peaks of their photoluminescence spectra originated around the band edge of hexagonal GaN. Electroluminescent devices based on amorphous GaN were fabricated and were found to show UV emission. Amorphous GaN is one of the candidate materials for light‐emitting devices operating in the UV to the blue spectral regions.

The recent improvements of complementary metal–oxide–semiconductor (CMOS) image sensors are playing an essential role in emerging high-definition video cameras, which provide viewers with a stronger sensation of reality. However, the devices suffer from decreasing sensitivity due to the shrinkage of pixels. We herein address this problem by introducing a hybrid structure comprising crystalline-selenium (c-Se)-based photoconversion layers and 8 K resolution (7472 × 4320 pixels) CMOS field-effect transistors (FETs) to amplify signals using the avalanche multiplication of photogenerated carriers. Using low-defect-level NiO as an electric field buffer and an electron blocking layer, we confirmed signal amplification by a factor of approximately 1.4 while the dark current remained low at 2.6 nA/cm2 at a reverse bias voltage of 22.6 V. Furthermore, we successfully obtained a brighter image based on the amplified signals without any notable noise degradation.

No abstract

Amorphous GaN films were deposited using a compound-source molecular beam epitaxy technique. Electroluminescent devices were also fabricated using the deposited films. The devices were operated using sine wave voltage at room temperature. One of the emission peaks was located in the UV spectral region. The deposition rate was increased by introducing a small ammonia flow.

In this study, we describe an active pixel sensor (APS) readout circuit using indium–tin–zinc-oxide (ITZO) thin-film transistors (TFTs). The APS readout circuit with a pixel size of 90 μm was fabricated using ITZO TFTs with a channel length of 2 μm, and its performance was experimentally evaluated. The ITZO TFTs were found to have good low-frequency noise performance with an extracted Hooge’s parameter (α H) of 3.5 × 10−3, and the APS exhibits a high DC voltage gain of ∼0.81 with satisfactory linearity in a wide output voltage range of ∼6.4 V as well as manageable response times of less than 15 μs. The obtained results show the potential of our APS circuits to be applied to TFT-based image sensors with enhanced image quality.

No abstract

No abstract