Jun Zheng

Enhanced photoluminescence from porous silicon nanowire arrays

The enhanced room-temperature photoluminescence of porous Si nanowire arrays and its mechanism are investigated. Over 4 orders of magnitude enhancement of light intensity is observed by tuning their nanostructures and surface modification. It is concluded that the localized states related to Si-O bonds and self-trapped excitations in the nanoporous structures are attributed to the strong light emission.

Silicon Based GeSn p-i-n Photodetector for SWIR Detection

We reported an investigation of GeSn-based p-i-n photodetectors (PDs) with a Ge0.92Sn0.08 active layer grown on n-type Si (100) substrate using molecular beam epitaxy (MBE). The GeSn photodetector achieved a wide spectrum detection whose cutoff wavelength can reach to 2.3 μm. The PDs exhibited a high performance near 2.0 μm with a responsivity of 93 mA/W and a dark current of 171 μA under a reverse bias of 1 V at room temperature. This work represented a promising technology to develop Si-based short-wave infrared (SWIR) photodetectors.

Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3-Si multilayer deposited on Si substrates

Eu2O3/Si multilayer nanostructured films are deposited on Si substrates by magnetron sputtering. Transmission electron microscopy and X-ray diffraction measurements demonstrate that multicrystalline Eu silicate is homogeneously distributed in the film after high-temperature treatment in N2. The Eu2+ silicate is formed by the reaction of Eu2O3 and Si layers, showing an intense and broad room-temperature photoluminescence peak centered at 610 nm. It is found that the Si layer thickness in nanostructures has great influence on Eu ion optical behavior by forming different Eu silicate crystalline phases. These findings open a promising way to prepare efficient Eu2+ materials for photonic application.

Insight into the effect of ligand-exchange on colloidal CsPbBr3 perovskite quantum dot/mesoporous-TiO2 composite-based photodetectors: much faster electron injection

In the current work, we fabricate an all-inorganic perovskite quantum dot-based photodetector with bifunctional linker molecules, which is highly superior to its counterpart without the linker. The ultrahigh on/off ratio of 105 is two orders of magnitude higher than that of the device without the ligand treatment. Moreover, the responsivity increases from ∼2.2 A W−1 to ∼24.5 A W−1 and the detectivity from 3.5 × 1012 Jones to 8.9 × 1013 Jones. To gain further insight into the effect of ligand-exchange by bifunctional linker molecules besides surface passivation, we divide the electron transfer process into two parts, the electron transfer from quantum dots (QDs) to the linker and from the linker to TiO2. Injection of photoexcited electrons from colloidal CsPbBr3 QDs into TiO2 nanoparticles by bifunctional linker molecules is found to be much faster. Continuous-wave and time-resolved fluorescence spectra exhibit strong quenching for CsPbBr3 QDs assembled by the linker or coupled to TiO2 nanoparticles, which is consistent with electron transfer for QDs. From the results of the transient absorption measurement and fluorescence lifetime, the electron transfer time of QDs–TiO2 linked by the bifunctional molecules is calculated to be within 40 ns, while that from QDs to TiO2 particles directly is estimated to be ∼290 ns. This indicates that much faster electron injection occurs under the effect of the electron linker. In addition, the linker molecule modification can improve the adsorption of mp-TiO2 to capture more QDs.

Single-crystalline Ge1-x-ySixSny alloys on Si (100) grown by magnetron sputtering

Magnetron sputtering was successfully used to grow single-crystalline Ge1-x-ySixSny ternary alloys on Si (100) substrates. The lattice constants of the alloys were calculated by X-ray diffraction and corrected Vegard’s law, respectively, showing that the corrected Vegard’s law is suitable for the Ge1-x-ySixSny lattice constants. Thermal stability investigations showed that the Ge0.85Si0.051Sn0.099 alloy was stable at 500 °C. The Ge1-x-ySixSny can maintain good crystalline quality under moderate annealing temperature, with no indication of phase segregation or Sn precipitation. Optical absorption measurements were carried out at room temperature to determine the band gap energies of the Ge1-x-ySixSny alloys. These results suggest that magnetron sputtering is an effective alternative method to grow Ge1-x-ySixSny alloys for fabrication of novel devices.

Ni(Ge 1− x − y Si x Sn y ) Ohmic Contact Formation on p-type Ge 0.86 Si 0.07 Sn 0.07

A single-crystalline Ge0.86Si0.07Sn0.07 alloy was grown on double Ge1− x Sn x and Ge buffers on Si (100) using magnetron sputtering. The temperature-dependent contact resistivity (

Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot

\rho _{\mathrm {c}})

Strained and strain-relaxed epitaxial Ge1−xSnx alloys on Si(100) substrates

of Ni/p-type Ge0.86Si0.07Sn0.07 structure was investigated in detail. Good ohmic contacts with

Impact of ammonia on the electrical properties of p-type Si nanowire arrays

\rho _{\mathrm {c}}

Thermoelectric transport through a quantum dot with a magnetic impurity

of