Publications by authors named "Michael R Braun"
Article Synopsis
- * The growth of the GeSn shell hinges on the balance between the delivery of a tin precursor and the surface area available for growth, affecting defects.
- * Optimal growth conditions exist that allow for uniform GeSn shell formation, preventing issues like wire bending or Sn-rich precipitates from occurring.
We investigate in-situ laser reflectometry for measuring the axial growth rate in chemical vapor deposition of assemblies of well-aligned vertical germanium nanowires grown epitaxially on single crystal substrates. Finite difference frequency domain optical simulations were performed in order to facilitate quantitative analysis and interpretation of the measured reflectivity data. The results show an insensitivity of the reflected intensity oscillation period to nanowire diameter and density within the range of experimental conditions investigated.
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- The paper presents the use of metal oxides, specifically nickel oxide (NiO) and titanium oxide (TiO), as carrier-selective contacts in ultrathin crystalline silicon solar cells, leading to about a 13% increase in efficiency.
- An ultrathin c-Si solar cell, only 2 μm thick, achieves efficiency over 10% without light-trapping, thanks to NiO's unique band offsets that reduce contact recombination.
- The integration process for both NiO and TiO is scalable and compatible with existing manufacturing techniques, enabling a champion efficiency of 10.8% when both materials are used.
Article Synopsis
- The performance of nanostructured semiconductors is often hindered by interface defects that trap electronic carriers, complicating traditional measurement methods to quantify these defects.
- Electrochemical impedance spectroscopy (EIS) is introduced as an effective technique for characterizing interface traps at metal oxide/semiconductor interfaces, utilizing liquid electrolytes for better electrical contact.
- The study demonstrates that EIS results correlate well with standard electrical testing, successfully applying this method to pyramid-nanostructured p-Si, showcasing its potential for measuring interface state densities in various semiconductor nanostructures.
Article Synopsis
- - Germanium-tin alloy nanowires show promise for creating efficient light-emitting devices that work well with silicon technology by achieving a direct band gap transition.
- - Free-standing nanowires can avoid elastic strains that usually hinder direct gap formation in traditional thin film structures, allowing for better light-emission characteristics.
- - The researchers successfully created core-shell nanowires, consisting of strained Ge core and unstrained GeSn shells, using low-temperature chemical vapor deposition, achieving high levels of Sn incorporation beyond typical limits.