Si-based Photodiodes Research Articles

Optical Modeling-Assisted Characterization of Polymer:Fullerene Photodiodes

In this paper, the practical viability of an organic bulk heterojunction (BHJ)-based photodiode is studied, including the analysis of dark current density ( $J_{d}$ in $hbox{A/cm}^{2}$), external quantum efficiency (EQE in percent), responsivity (R in A/W), noise-equivalent power (in $hbox{W/Hz}^{1/2}$), and specific detectivity (Jones in $hbox{cmHz}^{1/2}/hbox{W}$). The dark current was minimized down to 90 $hbox{pA/cm}^{2}$ in ${rm P}3{rm HT}:{rm PC}_{60}hbox{BM}$ BHJ photodiodes by increasing the thickness, whereas the EQE maintained high values. The measured noise current was $2.20times 10^{-13}$, $1.13times 10^{-13}$, and $1.94times 10^{-14} hbox{A/Hz}^{1/2}$ for 45-, 55-, and 65-nm BHJ photodiodes, respectively. With those values, the calculated detectivity obtained, given light of a 550 nm wavelength, was $2.55times 10^{11}$, $5.93times 10^{11}$, and $4.16times 10^{12}$ Jones, respectively. The results demonstrated a performance of polymer:fullerence photodiode near equivalent to that of Si-based photodiodes.

Multi-Layer Organic Squaraine-Based Photodiode for Indirect X-Ray Detection

The paper presents an organic-based photodiode coupled to a CsI(Tl) scintillator to realize an X-ray detector. A suitable blend of an indolic squaraine derivative and of fullerene derivative has been used for the photodiode, thus allowing external quantum efficiency in excess of 10% at a wavelength of 570 nm, well matching the scintillator output spectrum. Thanks to the additional deposition of a 15 nm thin layer of a suitable low electron affinity polymer, carriers injection from the metal into the organic semiconductor has been suppressed, and dark current density as low as has been obtained, which is comparable to standard Si-based photodiodes. By using a collimated X-ray beam impinging onto the scintillator mounted over the photodiode we have been able to measure current variations in the order of 150 pA on a dark current floor of less than 50 pA when operating the X-ray tube in switching mode, thus proving the feasibility of indirect X-ray detection by means of organic semiconductors.

Far-infrared electroluminescence characteristics of an Si-based photodiode under a forward DC bias current

At room temperature, the bias dependence of a far-infrared electroluminescence image of a photodiode is investigated in the dark condition. The results show that the electroluminescence image can be used to detect defects in the photodiode. Additionally, it is found that the electroluminescence intensity has a power law dependence on the dc bias current. The photodiode ideality factor could be obtained by a fitting a relationship between the electroluminescence intensity and the bias current. The device defect levels will be easily determined according to the infrared image and the extracted ideality factor value. This work is of guiding significance for current solar cell testing and research.

Nitride-based photodiode at 510-nm wavelength for plastic optical fiber communication

We demonstrate a GaN-based waveguide photodiode at a wavelength of around 510 nm for plastic optical fiber communication. Compared with the performance of an Si-based photodiode in the same wavelength regime, our device can achieve better external efficiency. It also enjoys the unique advantage of monolithic integration with the GaN-based green-amber light-emitting-diode (LED). Our demonstrated photodiode exhibits high external efficiency (73%) and a 600-MHz electrical bandwidth. Under forward bias, this device can also serve as a transmitter (LED), and the measured optical center wavelength is around 515 nm with a 70-MHz electrical bandwidth.

All Si-based optical interconnect for interchip signal transmission

Barriers to the commercial implementation of optical interconnects between integrated circuits (ICs) center around the fabrication of optical elements on wafers through conventional Si processes. Most other approaches for optical interconnects use direct bandgap emitters that require drastic changes in conventional fabrication processes. In this work, we demonstrate the ability to transmit electrical signals using Si-based components, i.e., the light was generated by biasing a p-n junction at avalanche breakdown voltage, light was coupled through a fiber cable made of SiO/sub 2/, and detected by an Si-based avalanche photodiode. Results presented demonstrate the switching behavior of the light emitter, transmission of the signal across the fiber, and measurement of the signal limited by the bandwidth of the receiver amplifier.

N-ZnO/p-Si photodiodes fabricated using ion-beam induced isolation technique

We report on the fabrication of a new Si-based photodiode that has both insulating ZnO and n-ZnO overlayers. Thin n-ZnO layer was deposited on p-Si at 480 °C by RF magnetron sputtering and an insulating ZnO film was subsequently deposited at room temperature using the same deposition method. Silicon ions at 100 keV with doses of 5 × 10 13, 5 × 10 14 and 5 × 10 15 cm −2 were implanted into n-ZnO area, that was in the outside of an active device window, for inter-device isolation. The dark leakage current of the implanted photodiode clearly decreases with the dose. As measured under red laser illumination of 670 nm, photoresponsivity of 0.28 A/W and quantum efficiency of about 50% were obtained from our new n-ZnO/p-Si photodiode.

Si/SiO2 resonant cavity photodetector

It has been shown earlier that GeSi/Si resonant-cavity photodiodes can achieve high speed without sacrificing quantum efficiency. In this letter, we report a Si-based resonant-cavity photodiode that utilizes a Si/SiO2 Bragg reflector. This structure is more compatible with standard Si processing technology than the GeSi/Si resonant-cavity photodiodes. The absorbing region is a 1-μm-thick polysilicon layer that has been annealed to enhance secondary grain growth and the bottom mirror consists of three quarter-wavelength pairs of Si and SiO2. After annealing the dark current was 9 μA at 1 V, the peak quantum efficiency was 44%, and the bandwidth was ≳1.4 GHz.