In this study, with the aim of achieving a high signal-to-noise ratio (SNR) in an electron-bombarded complementary metal-oxide semiconductor (EBCMOS) imaging chip, we analyzed the sources of noise using principles from low-light-level imaging and semiconductor theory, and established a physical computational model that relates the electron-multiplication layer to the noise characteristics of an EBCMOS chip in a uniformly doped structure with a P-type substrate. We conducted theoretical calculations to analyze the effects on noise characteristics of the passivation layer material and thickness, P-substrate doping concentration, P-substrate thickness, incident electron energy, and substrate temperature. By comparing the characteristics of pixel noise, dark current, multiplication electron numbers, and SNR under various structures, we simulated optimized structural parameters of the device. Our simulation results showed that the noise characteristics of the device could be optimized using an Al2O3 passivation thickness of 15 nm and substrate temperature of 260 K, and by decreasing the doping concentration and thickness of the P-type substrate and increasing the incident electron energy. The optimized SNR were 252 e/e. And the substantial impact of dark current noise, primarily governed by interfacial defects, on the overall noise characteristics of the device. This research offers theoretical support to develop EBCMOS imaging chips with high gain and SNR.
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A high-sensitivity, low-noise single photon avalanche diode (SPAD) detector was presented based on a 180 nm BCD process. The proposed device utilizes a p-implant layer/high-voltage n-well (HVNW) junction to form a deep avalanche multiplication region for near-infrared (NIR) sensitivity enhancement. By optimizing the device size and electric field of the guard ring, the fill factor (FF) is significantly improved, further increasing photon detection efficiency (PDE). To solve the dark noise caused by the increasing active diameter, a field polysilicon gate structure connected to the p+ anode was investigated, effectively suppressing dark count noise by 76.6%. It is experimentally shown that when the active diameter increases from 5 to 10 μm, the FF is significantly improved from 20.7% to 39.1%, and thus the peak PDE also rises from 13.3% to 25.8%. At an excess bias voltage of 5 V, a NIR photon detection probability (PDP) of 6.8% at 905 nm, a dark count rate (DCR) of 2.12 cps/μm2, an afterpulsing probability (AP) of 1.2%, and a timing jitter of 216 ps are achieved, demonstrating excellent single photon detection performance.
CZTS (Cu2ZnSnS4) is a quaternary semiconductor that is environmentally friendly, less expensive. In this paper, we report on the optimization and fabrication of CZTS-based heterojunction nanodevices for bifunctional applications such as solar cells and photodetectors. CZTS thin films were deposited on top of (Molybdenum) Mo-coated glass substrates via RF sputtering at 100 and 200 Watt. Rapid thermal processing (RTP) was used at 300, 400, and 500°C temperatures. CdS (Cadmium sulphide) was deposited on CZTS using a chemical bath deposition system with 3- and 5-minute (min) deposition times. ZnO (Zinc Oxide) and AZO (Aluminium doped Zinc Oxide) layers were deposited using RF (Radio Frequency) sputtering to create the solar device. XRD confirms the formation of a tetragonal structure with increased crystallinity due to the use of RTP. Raman reveals the characteristic Raman shift peak associated with CZTS at 336 and 335 cm−1. The FESEM shows a relationship with RTP temperature. Surface features, including grain size, vary with RTP temperature. The ideality factor is nearly 2, indicating imperfection in the Mo/CZTS interface. Schottky barrier height estimates range from 0.6 to 0.7 eV. Absorbance and transmittance show a predictable fluctuation with RTP temperature. Photovoltaic device was built using the higher crystalline feature of CZTS in conjunction with CdS deposited at 3 and 5 min. The efficiency of CdS deposited after 3 and 5 min was 1.15 and 0.97 percent, respectively. Fabricated devices were used for wavelength-dependent photodetection. This work demonstrated self-powered photodetection.
A monolithic integrated full-wave bridge rectifier consisted of horizontal Schottky-barrier diodes (SBD) is prepared based on 100 nm ultra-thin β-Ga2O3 and demonstrated the solar-blind UV (SUV) light-modulated characteristics. Under SUV light illumination, the rectifier has the excellent full-wave rectification characteristics for the AC input signals of 5 V, 12 V and 24 V with different frequencies. Further, experimental results confirmed the feasibility of continuously tuning the rectified output through SUV light-encoding. This work provides valuable insights for the development of optically programmable Ga2O3 AC-DC converters.
