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All astronomical missions use charge-coupled devices (CCDs) as vital organs. Usually, silicon (Si) is preferred to build them, which does not perform well without enhancements such as anti-reflection (AR) coatings. Such devices exhibit poor performance in the large (> 800 nm) and small (< 500 nm) wavelength ranges, even with AR coatings. We present studies that signify gallium nitride (GaN) as a potential replacement for Si in astronomical CCDs that operate in a wide wavelength range. For this purpose, SILVACO TCAD software has been used for simulating and comparing the electronic and optical properties of a GaN CCD pixel with a Gaia astrometric field (AF) CCD pixel. Our observations demonstrate that the electronic and optical performance of the GaN-based CCD pixel is significantly better than the Si-based AF CCD pixel. These findings can prove to be the bedrock of future astronomical exploration and broadband astronomical CCDs, as the simulated GaN CCD pixel exhibits a high quantum efficiency even without any reinforcements. [ABSTRACT FROM AUTHOR]

The demand for charge‐coupled device (CCD) imagers has surged exponentially during the last decade owing to their exceptionally high quality and low noise imaging. However, they are still confronting the performance constraints of high operation power, low speed, and limited charge integration. Here, the electric‐dipole gated phototransistor operation without external gate bias is reported by using high‐k HfO2 dielectric material. The electrostatic coupling of photogenerated charges from the Si with the graphene channel through a 10 nm HfO2 layer is demonstrated. The device exhibits remarkable performance in the broadband spectrum (266–1342 nm) at low drain bias voltage. The high values of responsivity, external quantum efficiency, and detectivity of 3.7 × 103 A W−1, 0.72 × 104, and 6.20 × 1013 cmHz½ W−1, respectively, for 800 nm wavelength and 3.3 × 103 A W−1, 1.31 × 104, and 5.61 × 1013 cmHz½ W−1, respectively, for 400 nm wavelength without gate are achieved. This discovery may potentially eliminate the requirement for gate terminals from commercial CCD devices. The power efficient features of this gateless image sensor can be fabricated at the industrial scale for the future machine vision market. [ABSTRACT FROM AUTHOR]

A 256-channel readout application specific integrated circuit (ASIC) called the very low-noise analog sampling engine (VASE) intended for the readout of column-parallel charge-coupled devices (CP-CCDs), is presented. Each channel uses a charge-sensitive amplifier and a first-order dual-gain sigma-delta analog-to-digital converter (ADC) that act as the front end of an extended counting ADC. The extended counting ADC directly implements correlated multiple-sampling as part of its operation. To reduce the noise due to input capacitance and to ensure a compact camera, the VASE input bonding pads are pitch matched to the CP-CCD to allow chip-to-chip bonding with minimal parasitic capacitance. The chip is designed in a modular way with each 16 input channels sharing a single differential analog output and digital serializer. VASE, with a die area of 38.1 mm2 and fabricated in 180-nm CMOS technology, achieves 22 e- equivalent noise charge (ENC) and a dynamic range of 190 ke- (78.7 dB) at a 4-MHz pixel rate (corresponding to a frame rate of 32 kfps when a 256 × 256 pixel sensor is read out on both sides) while dissipating 10.1 mW per channel. The prototype has been used to successfully image X-ray diffraction at a soft X-ray synchrotron.

Photodetector arrays are key component in image sensors. Charge‐coupled devices (CCD) based photodetection is widely used due to their high resolution, large sensitivity, and low noise. However, the complex device structure, destructive and sequential readout method are primary concerns in expanding its application scenarios. Here, a charge sampling photodetector (CSP) based on fully 2D absorption/dielectric/readout van der Waals heterostructures (vdWs) is reported. Photo‐charges generated in the absorption layer are stored in a potential well of the vdWs, which enables weak signal detection and imaging after the charge integration process. A stacked transistor in the readout layer then nondestructively maps out the collected charges in a random‐access manner with high fill factor. With a properly engineered absorption layer, CSP can realize broadband detection from visible to mid‐IR range at room temperature and low operation voltage. Our device combines the advantages of CCD and complementary metal‐oxide‐semiconductor image technology, which exemplifies a promising candidate for next‐generation photodetectors. [ABSTRACT FROM AUTHOR]

Charge-coupled devices (CCD) allow imaging by photodetection, charge integration, and serial transfer of the stored charge packets from multiple pixels to the readout node. The functionality of CCD can be extended to the non-destructive and in-situ readout of the integrated charges by replacing metallic electrodes with graphene in the metal-oxide-semiconductors (MOS) structure of a CCD pixel. The electrostatic capacitive coupling of graphene with the substrate allows the Fermi level tuning that reflects the integrated charge density in the depletion well. This work demonstrates the in-situ monitoring of the serial charge transfer and interpixel transfer losses in a reciprocating manner between two adjacent Gr-Si CCD pixels by benefitting the electrostatic and gate-to-gate couplings. We achieved the maximum charge transfer efficiency (CTE) of 92.4 % , which is mainly decided by the inter-pixel distance, phase clock amplitudes, switching slopes, and density of surface defects. The discussion on overcoming transfer losses and improving CTE by realizing a graphene-electron multiplication CCD is also presented. The proof of the concept of the in-situ readout of the out-of-plane avalanche in a single Gr-Si CCD pixel is also demonstrated, which can amplify the photo packet in a pre-transfer manner. [ABSTRACT FROM AUTHOR]

Abstract The compensation for non‐uniformity correction of multi‐channel time delay integration charge coupled device (TDI CCD) under variable gain is presented. The mathematical model of photoelectric conversion is established first, and, then, a two‐step non‐uniformity correction method for multi‐channel TDI CCD is proposed. Based on this method, a compensation algorithm for non‐uniformity correction under variable gain is elaborated in detail. The experimental results show that the proposed algorithm can always maintain the photo response non‐uniformity (PRNU) of the corrected images better than 1.14% when the programmable gain amplification (PGA) gain varies within the range of 1–3, compared to the conventional method of degrading to 2.91%. Meanwhile, a compression method for correction coefficients under multiple integral stages is proposed, which can reduce the storage space requirement by 50% at the cost of the PRNU being degraded by a maximum of 0.19% at all integral stages.

Charge-coupled devices (CCD) allow imaging by photodetection, charge integration, and serial transfer of the stored charge packets from multiple pixels to the readout node. The functionality of CCD can be extended to the non-destructive and in-situ readout of the integrated charges by replacing metallic electrodes with graphene in the metal-oxide-semiconductors (MOS) structure of a CCD pixel. The electrostatic capacitive coupling of graphene with the substrate allows the Fermi level tuning that reflects the integrated charge density in the depletion well. This work demonstrates the in-situ monitoring of the serial charge transfer and interpixel transfer losses in a reciprocating manner between two adjacent Gr-Si CCD pixels by benefitting the electrostatic and gate-to-gate couplings. We achieved the maximum charge transfer efficiency (CTE) of 92.4%, which is mainly decided by the inter-pixel distance, phase clock amplitudes, switching slopes, and density of surface defects. The discussion on overcoming transfer losses and improving CTE by realizing a graphene-electron multiplication CCD is also presented. The proof of the concept of the in-situ readout of the out-of-plane avalanche in a single Gr-Si CCD pixel is also demonstrated, which can amplify the photo packet in a pre-transfer manner.