Wafer Level High-Speed Germanium Photodiode Array Integration

In this work, a strategy of constructing a back-to-back heterojunction is proposed to fabricate Si-based photovoltaic photodetectors with high deep ultraviolet (DUV) spectral selectivity. By combining Pt with a thickness of 4 nm with a ZnGa2O4/Si heterojunction, a back-to-back heterojunction is successfully constructed. Based on that, a Pt/ZnGa2O4/p-Si DUV photovoltaic detector with a low dark current density (∼9.6 × 10-5 μA/cm2), a large photo-to-dark current ratio (PDCR, >105), and a fast response speed (decay time <50 ms) is fabricated. At 0 V bias, this device displays a photoresponsivity of about 1.36 mA/W and a high deep ultraviolet-visible (DUV-vis) rejection ratio (R258nm/R420nm) of ∼1.1 × 105, which are 1-2 orders of magnitude higher than those of most photovoltaic DUV detectors reported currently. Even at a working temperature of 470 K, the detectivity of this device can still reach ∼1.23 × 1010 Jones. In addition, compared with Au/ZnGa2O4/Si devices, the dark current and PDCR of this Pt/ZnGa2O4/Si device decrease by 2 orders of magnitude and increase by 1 order of magnitude, respectively. The enhanced performance of this ZnGa2O4/Si device can be attributed to the higher Schottky barrier established between Pt with a higher work function and ZnGa2O4. This strategy of adopting a back-to-back heterojunction device structure to hinder the visible light photoresponse of Si-based photodetectors and thus to reduce the dark current of a device can provide a reference for preparing photovoltaic DUV detectors with excellent performance.

There is a lot of interest in developing low noise avalanche photodiodes (APDs) in the short wave infrared (1.5-3 microns) and mid-wave infrared (3-5 microns). State of the art APDs are are based on based on interband transitions in mercury cadmium telluride (MCT, HgCdTe) with large multiplication gains and low excess noise factors due to the favorable bandstructure that promotes single carrier impact ionization. However, their dark currents are high (3-5e-4A/cm2 at a gain of 10 at 125K) that requires cryogenic cooling. We have investigated the multiplication characteristics of three different multipliers on InP substrate (AlGaInAs (M1), AlGaAsSb (M2) and AlInAsSb (M3)). We have demonstrated decrease in the excess noise factors using ternary superlattices and extremely low excess noise factors (k~0.01) and low dark current density (~10 A/cm2) at 300K. We will discuss the research challenges associated with the design, growth, fabrication and radiometric characterization of these APDs

Influence of shallow versus deep etching on dark current and quantum efficiency in InAs/GaSb superlattice photodetectors and focal plane arrays for long wavelength infrared detection

AlInAs/InGaAs metal-semiconductor-metal (MSM) photodetectors with a low dark current density are fabricated using a surface modification process with phosphine (PH3) plasma. Phosphidization of the AlInAs cap layer reduces the surface state density and allows formation of high Schottky barrier with a tunnel metal-insulator-semiconductor (MIS) structure. A dark current density as low as 0.021 pA/µm2 at 10 V is obtained.

Optimizing dot-in-a-well infrared detector architecture for achieving high optical and device efficiency corroborated with theoretically simulated model

Low dark current density plays a key role in determining the overall performance of perovskite photodetectors (PPDs). To achieve this goal, a hole transport layer (HTL) on the ITO side and a hole blocking layer (HBL) on the metal electrode side are commonly introduced in PPDs. Unlike traditional approaches, we realized a high-performance solution-processed broadband PPD using metal oxide (MO) nanoparticles (NPs) as the HBL on the ITO electrode and PC61BM as another HBL on the metal electrode side to reduce the device dark current. The PPDs based on TiO2 and SnO2 NP-modified layers show similar device performances at −0.5 V: a greater than 105 on/off ratio; over 100 dB linear dynamic range (LDR) under different visible light illumination; around 0.2 A W−1 responsivity (R); greater than 1012 jones detectivity (D*); and ∼20 μs rise time of the device. The MO NP interfacial layer can significantly suppress charge injection in the dark, while the accumulated photogenerated charges at the interface between the MO layer and the perovskite layer introduce band bending, leading to dramatically increased current under illumination. Therefore, the dark current density of the devices is significantly reduced and the optical gain is drastically enhanced. However, after UV illumination, the dark current of the TiO2 device dramatically increases while the dark current of the SnO2 device can stay the same as before since the UV illumination-induced conductivity and barrier height changes in the TiO2 layer cannot recover after removing the UV irradiation. These results indicate that the TiO2 NP layer is suitable for making a vis-NIR photodetector, while the SnO2 NP layer is a good candidate for UV-vis-NIR photodetectors. The facile solution-processed high-performance perovskite photodetector using MO NP-modified ITO is highly compatible with low cost, flexible, and large-area electronics.

Polycrystalline perovskites have attracted extensive interest in the field of X-ray detection/imaging due to their excellent compatibility with scalable processing. However, despite recent advances, polycrystalline perovskite X-ray direct detectors are plagued by the relatively high dark currents in imaging applications. Herein, we experimentally demonstrate that the dark current of polycrystalline perovskite X-ray detectors can be controlled by tuning the composition of perovskites. In particular, the incorporation of bromine (Br) into methylammonium lead iodide (MAPbI3) modifies the bandgap, increases electrical resistance, reduces the defects, improves the crystallinity, and suppresses the nonradiative recombination, thereby comprehensively causing the reduction of dark currents. At a doping concentration of 15%, the bulk resistivity of MAPb(I1-xBrx)3 layer increases to 1.3 × 108 Ω·cm, leading to a low dark current density down to 0.801 nA·cm-2. Consequently, the X-ray detector shows a low detection limit of 118.4 nGyair s-1 and a sensitivity to noise-current ratio of 7.27 × 1011 μC Gyair-1 A-1. By integrating the Br-doped MAPbI3 X-ray detector into a readout integrated circuit, the X-ray imager exhibits high-quality imaging capability. The results reveal a simple and effective strategy to minimize dark currents in perovskite X-ray detectors, and the detector has high potential in high-performance X-ray flat-panel imagers for industrial and medical applications.

Organic-inorganic hybrid perovskites are ideal materials for photodetection owing to their high charge carrier mobility, long charge carrier diffusion length, low dark current density and sharp absorption edge. However, a relatively small band gap (1.6 eV) limits their photon-harvesting efficiency in the near-infrared region. In the present work, we demonstrate a hybrid methylamine iodide and Pb-Sn binary perovskite as the light absorption layer in photodetectors. Experimentally, the wavelength of photoresponse onset for the photodetectors can be extended to as great as 1,000 nm when the Sn content of the hybrid perovskite is increased to 30 mol%. In addition, the photodetectors exhibit a photoresponsivity of 0.39 A W−1, a specific detectivity of 7×1012 Jones, a fast photoresponse with rise and decay time constants and an external quantum efficiency greater than 50% in the wavelength range of 350–900 nm, with a maximum value of about 80% at 550 nm.

In0.5Ga0.5As Bilayer Quantum Dot Heterostructure for mid-infrared photodetection

A bulk-heterojunction (BHJ) blend is commonly used as the photoactive layer in organic photodetectors (OPDs) to utilize the donor (D)/acceptor (A) interfacial energetic offset for exciton dissociation. However, this strategy often complicates optimization procedures, raising serious concerns over device processability, reproducibility and stability. Herein, we demonstrate highly efficient OPDs fabricated with single-component organic semiconductors via solution-processing. The non-fullerene acceptors (NFAs) with strong intrinsic D/A character are used as the photoactive layer, where the emissive intermolecular charge transfer excitonic (CTE) states are formed within <1ps, and efficient photocurrent generation is achieved via strong quenching of these CTE states by reverse bias. Y6 and IT-4F based OPDs show excellent OPD performances; low dark current density (∼10-9 A cm-2 ), high responsivity (≥ 0.15 A W-1 ), high specific detectivity (> 1012 Jones) and fast photo-response time (< 10 µs), comparable to the state-of-the-art BHJ OPDs. Together with strong CTE state quenching by electric field, these excellent OPD performances are also attributed to the high quadrupole moments of NFA molecules, which can lead to large interfacial energetic offset for efficient CTE dissociation. Our work opens a new way to realize efficient OPDs using single-component systems via solution-processing and provides important molecular design rules. This article is protected by copyright. All rights reserved.

We report the growth, fabrication and characterization of Al/sub 0.4/Ga/sub 0.6/N-Al/sub 0.6/Ga/sub 0.4/N back-illuminated, solar-blind p-i-n photodiodes. The peak responsivity of the photodiodes is 27 and 79 mA/W at /spl lambda//spl ap/280 nm for bias voltages of 0 V and -60 V, respectively, with a UV-to-visible rejection ratio of more than three decades (at 400 nm). These devices exhibit very low dark current densities (/spl sim/5 nA/cm/sup 2/ at -10 V). At low frequencies, the noise exhibits a 1/f-type behavior. The noise power density is S/sub 0//spl ap/5/spl times/10/sup -25/ A/sup 2//Hz at -12.7 V and the detectivity (D*) at 0 V is estimated to be in the range of 4/spl times/10/sup 11/-5/spl times/10/sup 13/ cm/spl middot/Hz/sup 1/2//W. Time-domain pulse response measurements in a front-illumination configuration indicate that the devices are RC-time limited and show a strong spatial dependence with respect to the position of the incident excitation, which is mainly due to the high resistivity of the p-type Al/sub 0.4/Ga/sub 0.6/ N layer.

A metal–semiconductor–metal (MSM) detector for low energy backscattered electrons has been developed and tested. The effects of detector symmetry, finger spacing, and detection area on signal to dark current ratio were studied in order to determine an optimized detector geometry. The detector assembly consisting of Ni-GaAs MSM structures with low dark current densities was mounted in a scanning electron microscope on a special sample holder which enabled the test of the detector under conditions which can be expected in electron beam microcolumn applications. With this experimental setup, backscattered electron images of alignment marks of 50-nm-thick Au on a Si substrate were obtained. The signal to noise performance of the device has been compared to a commercial Everhart–Thornley detector. It is demonstrated that MSM detectors can be used as backscattered electron detectors in microcolumns.

Lateral InGaAs p-n and p-n-p photodiodes were fabricated by area-selective diffusion of Zn through Al/sub 2/O/sub 3/ masks. Low dark current densities and a carrier transit-time limited frequency behavior were found. P-n diodes show a 3 dB bandwidth of 19 GHz for an electrode separation of 4 /spl mu/m. High optical gain was obtained with the lateral p-n-p structure leading to a responsivity of 6-8 A/W in the wavelength range between 1.0 and 1.6 /spl mu/m, which is considerably more than with the p-n device and conventional MSM detectors.

Initial results on the MWIR e-APD detector arrays with 30 μm pitch fabricated on LPE grown compositionally graded p-HgCdTe epilayers are presented. High dynamic resistance times active area (R0A) product 2 × 106 Ω-cm2, low dark current density 4 nA/cm2 and high gain 5500 at -8 V were achieved in the n+-υ-p+ HgCdTe e-APD at 80 K. LPE based HgCdTe e-APD development makes this technology amenable for adoption in the foundries established for the conventional HgCdTe photovoltaic detector arrays without any additional investment.

Infrared photodetectors and technology have experienced half a century of development. Two generation detectors have appeared: the first generation is mechanical scanning unit or linear array detectors, the second-generation is staring focal plane array detectors. It has formed a huge family of infrared detectors. Recent years, people gradually raised to the technical concept of third-generation infrared detectors which have high detecivity, large formate, low-cost,and multi-spectral response. Antimonide based type-Ⅱ InAs/GaSb superlattice has several fundamental properties that make it suitable for third-generation infrared detection technology: high quantum efficiency, low dark current density, tunable bandgap, high uniformity, and low cost. In this paper, we review the recent domestic and international research in third-generation infrared detector material and devices. and we focus on clarifying advantages of antimonide based type Ⅱ superlattice material and the development status at home and abroad. By analyzing the technology development process in a number of key research institutions, we hope to clarify the challenges and research trends of antimonide material in the next few years.