P-type FZ Silicon Research Articles

A Comparative study by TCAD Simulation for two different planar n-on-p silicon particle detectors with different guard ring implant type

In this paper, we compare two multi-guard ring geometries for n-on-p silicon particle detectors for high luminosity applications. One structure has p-type guard rings while the other has n-type guard rings with p-stop isolation between n+ implants. The pre-irradiation performance of the guard ring structures are studied as a function of oxide charge. It is found that for both structures, there is a value of oxide charge for which the breakdown voltage is maximum. The post-irradiation performance of the structures are evaluated with simulations up to a radiation fluence of 1×10+16 neq/cm2 using an existing three-level trap model for p-type FZ silicon. TCAD simulation has been used to simulate I-V characteristics, charge carrier concentration, electric field, and potential distribution.

Analysis and Optimization of the Bulk and Rear Recombination of Screen-Printed PERC Solar Cells

In this paper, we investigate the impact of the rear surface passivation, the silicon base material and the local aluminum contacts applied to rear side passivated solar cells with a homogenously doped emitter at the front. We compare different dielectric surface passivation layers (SiO2, Al2O3, SiNx) on a high-efficiency level using 125×125 mm2 and 156×156 mm2 p-type Cz silicon wafers. It turns out that applying an Al2O3/SiNx layer stack outperforms all other surface passivation layers due to its excellent surface passivation as well as optical properties. We determine the impact of the light induced degradation depending on the used Cz base material. We measure an efficiency drop between 0.0% (Ga-doped) and 0.8% abs. (B-doped) after 8hours of illumination under 0.5 Suns. We measure the surface recombination velocity of local screen-printed Al contacts with varying the metallisation fraction frear with the dynamic infrared lifetime mapping technique (dyn-ILM) on lifetime samples. We measure a decrease in contact recombination velocity from above 1100cm/s for small frear to 400cm/s for large frear on 1.5Ωcm p-type FZ-silicon. Microscopy investigations show that this is due to an improved local Al-BSF formation when using higher frear.

Amorphous silicon carbide heterojunction solar cells on p-type substrates

The performance of silicon heterojunction (SHJ) solar cells is discussed in this paper in regard to their dependence on the applied amorphous silicon layers, their thicknesses and surface morphology. The emitter system investigated in this work consists of an n-doped, hydrogenized, amorphous silicon carbide a-SiC:H(n) layer with or without a pure, hydrogenized, intrinsic, amorphous silicon a-Si:H(i) intermediate layer. All solar cells were fabricated on p-type FZ-silicon and feature a high-efficiency backside consisting of a SiO 2 passivation layer and a diffused local boron back surface field, allowing us to focus only on the effects of the front side emitter system. The highest solar cell efficiency achieved within this work is 18.5%, which is one of the highest values for SHJ-solar cells using p-type substrates. A dependence of the passivation quality on the surface morphology was only observed for solar cells including an a-Si:H(i) layer. It could be shown that the fill factor suffers from a reduction due to a reduced pseudo fill factor for emitter thicknesses below 11 nm due to a lower passivation quality and/or a higher potential for shunting thorough the a-Si emitter to the crystalline wafer with the conductive indium tin oxide layer. Furthermore, the influence of a variation of the doping gas flow ( PH 3 ) during the plasma enhanced chemical vapor deposition of the doped amorphous silicon carbide a-SiC:H(n) on the solar cell current–voltage characteristic-parameter has been investigated. We could demonstrate that a-SiC:H(n) shows in principle the same dependence on PH 3 -flow as pure a-Si:H(n).

Guard Ring Simulations for n-on-p Silicon Particle Detectors

We propose a new guard ring geometry for n-on-p silicon particle detectors for high luminosity applications. The performance of the guard ring structure is evaluated with simulations up to a radiation fluence of 1 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eq</sub> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> using an existing three level trap model for p-type FZ silicon. The post-irradiation performance improvement of guard rings with floating field plates pointing towards the sensitive region is demonstrated. The breakdown behavior of the guard ring structure is studied as a function of oxide charge, field plate length, and oxide thickness.

Materials Optimization for Silicon Heterojunction Solar Cells Using Spectroscopic Ellipsometry

AbstractOur research team has used hot wire chemical vapor deposition (HWCVD) to fabricate silicon heterojunction (SHJ) solar cells on p-type FZ silicon substrates with efficiencies as high as 18.2%. The best cells are deposited on anisotropically-textured (100) silicon substrates where an etching process creates pyramidal facets with (111) crystal faces. Texturing increases Jsc through enhanced light trapping, yet our highest Voc devices are deposited on un-textured (100) substrates. One of the key factors in maximizing the efficiency of our SHJ devices is the process of optimization of the material properties of the 3 - 5 nm thick hydrogenated amorphous silicon (a-Si:H) layers used to create the junction and back contact in these cells. Such optimization is technically challenging because of the difficulty in measuring the properties of extremely thin layers. This difficulty is compounded by the fact that the properties of such amorphous layers are substrate- and thickness-dependent. In this study, we have utilized spectroscopic ellipsometry (SE) and photoconductivity decay to conclude that a-Si:H films grown on (111) substrates are substantially similar to films grown on (100) substrates. In addition, analysis of the substrate temperature dependence of surface roughness evolution reveals a substrate-independent mechanism of surface smoothening with an activation energy of 0.28 eV. Analysis of the substrate temperature dependence of surface passivation reveals a passivation mechanism with an activation energy of 0.63 eV.

Electrical Properties of Silver Impurities and their Annealing Behaviour in p-Type Fz Silicon

The electrical activity of silver as well as its annealing properties in 10 Ω cm p-type Fz silicon substrate are studied by means of the four-point probe and minority carrier lifetime measurements. Silver atom concentration in the range 10 14 to 10 15 cm -3 consistently showed a donor type behaviour in the material and its presence led to a reduction of up to two orders of magnitude in the lifetime of minority carriers by the formation of deep-level traps. Isochronal annealing of silver contaminated specimens showed some gettering of the Ag impurities with resulting temperature dependent changes in the resistivity as well as the minority carrier lifetime values. Analysis of our results shows that a large fraction of the silver impurity atoms present forms the deep level defects and both the deep- and donor-levels appear to originate from the same source.

Studies of implanted iron in silicon by channeling and Rutherford backscattering

Different amounts of 100-keV iron ions have been implanted into high-resistivity p-type FZ-silicon samples. The implantation damage, recovery of damage during various annealing periods and temperatures, movement of iron atoms under annealing and oxidation, and the kinds of defects created after implantation, annealing, or oxidation are all investigated by channeling and backscattering measurements. We have found that the critical fluence of 100-keV iron implanted into silicon at room temperature is ∼2.5×1014 Fe/cm2, and that iron atoms are gettered by silicon oxidation. In this supersaturated region iron atoms diffuse slightly towards bulk silicon during high-temperature annealing (≥1100 °C) but not at all during low-temperature annealing (≤1000 °C) in dry nitrogen ambient.