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The vertical charge transport through Si/SiOx multiple quantum wells (QWs) is investigated. Upon thermal annealing, segregation of excess Si from the SiOx layers leads to the formation of highly conductive pathways between Si grains from adjacent QWs separated by ultrathin silicon oxide barriers with barrier heights of 0.53–0.65 eV. Compared to stoichiometric Si/SiO2 layer stacks, conductivity is increased by up to ten orders of magnitude, which opens the way to an efficient charge carrier extraction in photovoltaic systems with distinct quantum confinement. [ABSTRACT FROM AUTHOR]

In this paper, we study both theoretically and experimentally the sensitivity of bimodal interferometric sensors where interference occurs between two plasmonic modes with different properties propagating in the same physical waveguide. In contrast to the well-known Mach–Zehnder interferometric (MZI) sensor, we show for the first time that the sensitivity of the bimodal sensor is independent of the sensing area length. This is validated by applying the theory to an integrated plasmo-photonic bimodal sensor that comprises an aluminum (Al) plasmonic stripe waveguide co-integrated between two accessible SU-8 photonic waveguides. A series of such bimodal sensors utilizing plasmonic stripes of different lengths were numerically simulated, demonstrating bulk refractive index (RI) sensitivities around 5700 nm/RIU for all sensor variants, confirming the theoretical results. The theoretical and numerical results were also validated experimentally through chip-level RI sensing experiments on three fabricated SU-8/Al bimodal sensors with plasmonic sensing lengths of 50, 75, and 100 μm. The obtained experimental RI sensitivities were found to be very close and equal to 4464, 4386, and 4362 nm/RIU, respectively, confirming that the sensing length has no effect on the bimodal sensor sensitivity. The above outcome alleviates the design and optical loss constraints, paving the way for more compact and powerful sensors that can achieve high sensitivity values at ultra-short sensing lengths. [ABSTRACT FROM AUTHOR]

In this paper we demonstrate that an additional nitrous oxide (N 2 O) plasma treatment step after the regular SiN x :H anti-reflective coating (ARC) deposition practically eliminates background plating during Ni–Cu contact metallization for c-Si solar cells. This step is relatively simple and could henceforth enable the commercialization of plated Ni–Cu contacts, which is currently inhibited by the creation of localized metal-silicon interfaces due to background plating, among other issues like adhesion. The average active area efficiency and fill-factor of reference cells without any plasma treatment are 17.4% and 73.5%, respectively. N 2 O plasma treatment before ARC deposition leads to an improved average fill-factor of 75.0%. This improvement is attributed to a reduction in the area affected by background plating by approximately 40% due to the formation of a thin silicon oxy-nitride layer. N 2 O plasma treatment after ARC deposition is even more effective and can overcome background plating with an average active area cell efficiency and fill-factor of 18.5% and 77.5%, respectively. This performance improvement is attributed to oxidation of the ARC surface by the plasma post-treatment. Analysis of background plating losses is complemented by current–voltage curve fits to a 3-diode model with resistance limited recombination, performed by the freely available program “2/3-Diode Fit”. [ABSTRACT FROM AUTHOR]

Abstract: In this work we report for the first time on the creation of thermal acceptors after laser irradiation of a phosphorous doped p-type silicon substrate in ambient atmosphere. The concentration of these defects up to 1020 cm−3 is leading to a conductivity change from n- to p-type just beneath the surface. Electrochemical capacitance voltage (ECV) measurements followed by resistivity measurements confirm this conversion of conductivity. Secondary ion mass spectrometry (SIMS) measurements show significant oxygen incorporation after laser irradiation. The comparison of saturation current density and lock-in thermography measurements of processed wafers in ambient and in nitrogen atmosphere reveal that these defects are electrically active recombination centres that disappear in absence of oxygen. In simulations of the temperature profile during laser processing a correlation between the pulse energy density (E P ) and the appearance of thermal acceptors has been observed. The influence of these laser induced acceptor defects on solar cell parameters has been finally investigated. An efficiency loss of 1.3% absolute pertinent to pulse energies usually applied in laser doping process under ambient atmosphere could be avoided by laser processing in nitrogen atmosphere. [Copyright &y& Elsevier]

2D materials display very promising intrinsic material properties, with multiple applications in electronics, photonics, and sensing. In particular layered platinum diselenide has shown high potential due to its layer‐dependent tunable bandgap, low‐temperature growth, and high environmental stability. Here, the conformal and area selective (AS) low‐temperature growth of layered PtSe2 is presented defining a new paradigm for 2D material integration. The thermally‐assisted conversion of platinum which is deposited by AS atomic layer deposition to PtSe2 is demonstrated on various substrates with a distinct 3D topography. Further the viability of the approach is presented by successful on‐chip integration of hybrid semiconductor devices, namely by the manufacture of a highly sensitive ammonia sensors channel with 3D topography and fully integrated infrared‐photodetectors on silicon photonics waveguides. The presented methodologies of conformal and AS growth therefore lay the foundation for new design routes for the synthesis of more complex hybrid structures with 2D materials. [ABSTRACT FROM AUTHOR]

Abstract: The SiC/SiOx hetero-superlattice (HSL) consisting of alternating near-stoichiometric SiC barrier layers for the electrical transport and silicon rich SiOx matrix layers for the quantum dot formation is a promising approach to the realization of silicon quantum dot (Si–QD) absorbers for 3rd generation solar cells. However, additional defect states are generated during post deposition annealing needed for the Si–QD formation causing an increase in sub-band gap absorption and a decrease in PL intensity. Proper passivation of excess defects is of major importance for both the optical and electrical properties of the SiC/SiOx HSL Si–QD absorber. In this work, we investigate the effectiveness of the hydrogen reincorporation achieved with hydrogen plasma in a plasma-enhanced chemical vapor deposition (PECVD) reactor, hydrogen dissociation catalysis in hot-wire chemical vapor deposition (HWCVD) reactor and annealing in forming gas atmosphere (FGA). Both the HSL samples and single layer reference samples are tested. The passivation quality of the hydrogen reincorporation was examined by comparing electrical and optical properties measured after deposition, after annealing and after passivation. In addition, the formation of Si–QDs in SiC/SiOx HSL was evaluated using high resolution transmission electron microscopy. We demonstrated that hydrogen can be successfully reincorporated into the annealed HSL sample and its single layer reference samples. FGA passivation is most effective for SiO1.2 single layers and HSL samples. Passivation with PECVD appeared to be only effective for SiC single layers. [Copyright &y& Elsevier]