Experimental study of the effect of junction curvature on breakdown voltage in Si

Speeney, D. V.; Carey, Glen P.

doi:10.1016/0038-1101(67)90071-8

Cited by 20 publications

(6 citation statements)

References 3 publications

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“…For such a small radius of curvature of the p-n junction, the electric field becomes significantly enhanced due to the electrostatic tip effect, which leads to a reduction in breakdown voltage. This has been shown theoretically by Sze and Gibbons [15], whose results were confirmed experimentally by Speeney and Carey [16]; it was found that for an abrupt spherical p-n junction, a breakdown voltage of -13 V corresponds to a junction radius of 0.3 µm. This is in excellent agreement with the present data.…”

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confidence: 66%

Hot spots in multicrystalline silicon solar cells: avalanche breakdown due to etch pits

Bauer

Wagner

Lotnyk

et al. 2009

Physica Rapid Research Ltrs

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Solar cells whose breakdown current exceeds a certain limit cannot be used because such cells may thermally damage the module in case of unintentional reverse biasing by local shading (hot-spot problem [1]). In order to reduce the number of off-specification cells, the reason for the high reverse currents must be identified. The physical mechanisms leading to breakdown of reverse-biased p-n junctions are internal field emission (Zener effect) and impact ionization (avalanche effect). They exhibit a characteristic temperature dependence, which can be used for their identification: for internal field emission the current increases slightly with rising temperature due to band-gap lowering, but it decreases considerably for impact ionization due to increased phonon scattering. Moreover, multiplication of photo-generated carriers takes place only for avalanche breakdown [2]. Both mechanisms require a certain electric field strength, which normally is not reached in standard multicrystalline (mc) Si solar cells. According to that field strength, however, the breakdown voltage should be four times higher than observed in practice [3].In this letter, we present a systematic study of the breakdown mechanism in commercial, 156 × 156 mm 2 p-type base mc-Si solar cells. We employ special lock-in thermography (LIT) imaging techniques to identify the type of breakdown occurring at the hot spots, and various electron microscopy techniques to reveal the microscopic nature of the breakdown sites. The cells investigated were free from ohmic shunts. A typical reverse current-voltage characteristic is shown in Fig. 1, given for two different temperatures.At lower reverse voltages, only weak currents occur, which up to approximately -13 V increase only slightly (pre-breakdown). Beyond -13 V, however, a steep current increase is observed, which is typical for a hard breakdown. For the solar cells under investigation, the pre-breakdown current increases with temperature, whereas the hardbreakdown current decreases (for a given voltage). This indicates that in general, different breakdown mechanisms are involved, a fact which also other authors have observed, using electroluminescence (EL) at reverse bias [4].Lock-in thermography has been established as a standard technique for locating and characterizing leakage currents in solar cells [5]. For the investigation of breakdown currents we have recently proposed several LIT-based imaging techniques [6], performed either in the dark (DLIT) or under illumination (ILIT). In all these techniques, the -90° LIT signal, which can be interpreted quantitatively [7], is used. The temperature variation of the current at a given bias voltage is displayed by the Temperature-Coef-Multicrystalline silicon solar cells typically show hard breakdown beginning from about -13 V bias, which leads to the well-known hot-spot problem. Using special lock-in thermography techniques, hard breakdown has been found to occur in regions of avalanche multiplication. A systematic study of these regions by various electro...

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supporting

confidence: 66%

Hot spots in multicrystalline silicon solar cells: avalanche breakdown due to etch pits

Bauer

Wagner

Lotnyk

et al. 2009

Physica Rapid Research Ltrs

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“…The primary issue was the sharp corners created by the square geometry. Sharp corners are known to concentrate the electric field which lead to selective breakdown [ 54 , 55 , 56 ]. This resulted in limited photon detection probability (PDP) and increased timing jitter due to the non-uniform electric field.…”

Section: Cmos Photodetectors Using Current-assistancementioning

confidence: 99%

An Overview of CMOS Photodetectors Utilizing Current-Assistance for Swift and Efficient Photo-Carrier Detection

Jegannathan

Seliuchenko

Dries

et al. 2021

Sensors

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This review paper presents an assortment of research on a family of photodetectors which use the same base mechanism, current assistance, for the operation. Current assistance is used to create a drift field in the semiconductor, more specifically silicon, in order to improve the bandwidth and the quantum efficiency. Based on the detector and application, the drift field can be static or modulated. Applications include 3D imaging (both direct and indirect time-of-flight), optical receivers and fluorescence lifetime imaging. This work discusses the current-assistance principle, the various photodetectors using this principle and a comparison is made with other state-of-the-art photodetectors used for the same application.

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“…The quantum efficiency of this CASPAD is calculated to be 47%, at a wavelength of 785 nm, from the measured responsivity (~0.3 A/W) from our previous work [14]. The low probability of avalanche breakdown by an electron (~12.2% max) for the CASPAD is primarily attributed to the square geometry of the p-n junction, the breakdown occurs at the sharp corners due to high concentration of electric field at sharp edges in a similar way to premature edge breakdown [17,18]. Further investigation by light emission tests confirms that the breakdown occurs at the sharp corners (shown in Figure 6).…”

Section: Photon Detection Probabilitymentioning

confidence: 83%

Current-Assisted Single Photon Avalanche Diode (CASPAD) Fabricated in 350 nm Conventional CMOS

2020

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A current-assisted single-photon avalanche diode (CASPAD) is presented with a large and deep absorption volume combined with a small p-n junction in its middle to perform avalanche trigger detection. The absorption volume has a drift field that serves as a guiding mechanism to the photo-generated minority carriers by directing them toward the avalanche breakdown region of the p-n junction. This drift field is created by a majority current distribution in the thick (highly-resistive) epi-layer that is present because of an applied voltage bias between the p-anode of the avalanching region and the perimeter of the detector. A first CASPAD device fabricated in 350-nm CMOS shows functional operation for NIR (785-nm) photons; absorbed in a volume of 40 × 40 × 14 μm3. The CASPAD is characterized for its photon-detection probability (PDP), timing jitter, dark-count rate (DCR), and after pulsing.

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Experimental study of the effect of junction curvature on breakdown voltage in Si

Cited by 20 publications

References 3 publications

Hot spots in multicrystalline silicon solar cells: avalanche breakdown due to etch pits

Hot spots in multicrystalline silicon solar cells: avalanche breakdown due to etch pits

An Overview of CMOS Photodetectors Utilizing Current-Assistance for Swift and Efficient Photo-Carrier Detection

Current-Assisted Single Photon Avalanche Diode (CASPAD) Fabricated in 350 nm Conventional CMOS

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