One of the most common approaches for quenching single-photon avalanche diodes is to use a passive resistor in series with it. A drawback of this approach has been the limited recovery speed of the ...single-photon avalanche diodes. High resistance is needed to quench the avalanche, leading to slower recharging of the single-photon avalanche diodes depletion capacitor. We address this issue by replacing a fixed quenching resistor with a bias-dependent adaptive resistive switch. Reversible generation of metallic conduction enables switching between low and high resistance states under unipolar bias. As an example, using a Pt/Al
O
/Ag resistor with a commercial silicon single-photon avalanche diodes, we demonstrate avalanche pulse widths as small as ~30 ns, 10× smaller than a passively quenched approach, thus significantly improving the single-photon avalanche diodes frequency response. The experimental results are consistent with a model where the adaptive resistor dynamically changes its resistance during discharging and recharging the single-photon avalanche diodes.
We report InGaAs/InP based p-i-n photodiodes with an external quantum efficiency (EQE) above 98% from 1510 nm to 1575 nm. For surface normal photodiodes with a diameter of 80 µm, the measured 3-dB ...bandwidth is 3 GHz. The saturation current is 30.5 mA, with an RF output power of 9.3 dBm at a bias of -17 V at 3 GHz.
This paper reports the design, fabrication, and test of a 3-D integrated uncooled focal plane array (FPA) using monocrystalline silicon diodes as thermosensitive devices. The diode array is ...fabricated from the silicon device layer of a silicon-on-insulator wafer, and the readout integrated circuits (ROICs) are fabricated on a bulk wafer using the CMOS technology. The silicon diode array is vertically integrated with the ROIC using the 3-D integration technology. Electroless nickel (Ni) plating is developed for fabricating substantial Ni posts to mechanically support the diode pixels to suspension and electrically connect the diode pixels to the ROIC. It allows the integration of monocrystalline device arrays with CMOS circuits fabricated using separate technologies and wafers in vertically suspended configuration. It also improves the filling factors of the FPA chips, shortens the wires between the diodes and the ROIC, and facilitates the releasing process to suspend the diode array. A 160×120 small-scale FPA has been developed as a test vehicle for concept verification. The test results and successful thermal imaging demonstrate the feasibility of the 3-D integration technology and verify the application of 3-D integration in the development of integrated FPAs using monocrystalline thermosensitive devices.
This paper presents a method for fabrication of flexible silicon sensor chips using temporary bonding, backside thinning, debonding, and flexible packaging. Flexibility of silicon chips requires ...ultrathin thickness, which imposes a challenge to debonding of thinned silicon chips from carrier wafers because of the fragility of silicon. To address this problem, temporary bonding using polypropylene carbonate (PPC), a heat-depolymerizable polymer material, as bonding adhesive is developed. PPC allows damage-free detachment of ultrathin silicon chips from carrier wafers by heating after backside thinning. The method is demonstrated and applied to the fabrication of silicon stress sensor chips with thickness down to 30~\mu \text{m} . The measurement results show that the ultrathin silicon chips have good flexibility and function well. The processes are optimized, and the detailed parameters are reported. The preliminary results demonstrate the feasibility of the method, and show its potential application in the fabrication of flexible ultrathin silicon sensors.
A technical challenge in fabrication of ultra-thin sensor chip (UTSC) is to keep chip integrity in debonding the ultra-thin chips from grinding facilities. This paper presents a new debonding method ...by utilizing a thermally decomposable polypropylene carbonate (PPC), as the temporary bonding adhesive. Because PPC can readily decompose at relatively low temperature, this method can maintain the chip integrity even the chips have a thickness of tens of microns. UTSCs with thickness of 30μm have been achieved using this method, and stress sensors have been developed to verify the performance of UTSC. The experimental results show that the proposed method is able to fabricate UTSC with good flexibility and characterizations, demonstrating the newly proposed method an enabling technology for fabrication of sensors for flexible and wearable applications.
Abstract
The fast development of mid-wave infrared photonics has increased the demand for high-performance photodetectors that operate in this spectral range. However, the signal-to-noise ratio, ...regarded as a primary figure of merit for mid-wave infrared detection, is strongly limited by the high dark current in narrow-bandgap materials. Therefore, conventional mid-wave infrared photodetectors such as HgCdTe require cryogenic temperatures to avoid excessively high dark current. To address this challenge, we report an avalanche photodiode design using photon-trapping structures to enhance the quantum efficiency and minimize the absorber thickness to suppress the dark current. The device exhibits high quantum efficiency and dark current density that is nearly three orders of magnitude lower than that of the state-of-the-art HgCdTe avalanche photodiodes and nearly two orders lower than that of previously reported AlInAsSb avalanche photodiodes that operate at 2 µm. Additionally, the bandwidth of these avalanche photodiodes reaches ~7 GHz, and the gain–bandwidth product is over 200 GHz; both are more than four times those of previously reported 2 µm avalanche photodiodes.
This paper reports reactive ion etching (RIE) of poly (cyclohexene carbonate) (PCC), a thermal decomposable polymer that can be used as a sacrificial material for fabrication of embedded micro ...cavities and channels. The dependence of etching rate and anisotropy on RF power, chamber pressure, and O2 flow rate has been investigated. Experimental results show that all these parameters have influences on etching rate and anisotropy, and RF power and chamber pressure are, respectively, the two dominant factors that affect etching rate and anisotropy. Etching rate can be increased at high RF power, optimal chamber pressure and optimal O2 flow rate. Etching anisotropy can be improved by using high RF power, low chamber pressure, and low O2 flow rate.
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•RIE etching of heat-depolymerizable poly (cyclohexene carbonate) (PCC) has been investigated.•The dependence of etching rate and anisotropy on RF power, chamber pressure, and O2 flow rate are reported.•Etching rate of 360 nm/min and a sidewall angle about 85° have been obtained.
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