Effects of Fe doping on the strain and optical properties of GaN epilayers grown on sapphire substrates

Abstract

The effects of Fe doping on a series of Fe-doped GaN epilayers with different doping concentrations grown on sapphire substrates were investigated in detail by confocal micro-Raman spectroscopy under the backscattering geometric configuration. Careful investigation of the E high 2 and A 1 (LO) modes of the Fe-and Sidoped epilayers as well as the intentionally undoped free-standing GaN reveals that the compressive residual strain in the Fe-doped GaN epilayers tends to relax as the Fe concentration increases. This finding is further supported by X-ray diffraction measurements. The relaxation of compressive residual strain is most likely due to compensation by the tensile strain induced by incorporation of iron atoms in the GaN epilayers. The influence of Fe doping on the background electron concentration was also discussed by analyzing the upper branch of the A 1 (LO)-plasmon coupled mode.

Flexible Broadband Image Sensors with SnS Quantum Dots/Zn2SnO4 Nanowires Hybrid Nanostructures

“…Through decorating p-type SnS QDs on the surface of n-type ZTO NWs, nanoscale p-n heterojunctions are formed between SnS QDs and ZTO NWs. [11,18,21] Then a built-in electric field forms in the interface of SnS and ZTO, and leads to an upward band bending from ZTO to SnS. As a result, a quasi-type II heterostructure band structure is formed between SnS and ZTO, as shown in Figure 3c.…”

“…This method may improve the charge transfer between NWs and QDs because of without long and insulating ligands on the surface of QDs. [20,21] To control SnS particles size and distribution, we tried different SnS deposition times of 5, 10, 20, 30, and 60 min. Figure 1c displays the high-magnification SEM image of the assynthesized SnS decorated ZTO NW with a SnS deposition time of 10 min.…”

Flexible Photodetectors Based on Novel Functional Materials

“…They also fabricated UV-Visible-NIR sensitive photodetectors consisting of ZnO NWs array decorated with PbS QDs, which exhibit wider spectral response range and enhanced response speed with good stability, however, at the cost of slightly decreased photoresponsivity. [106] The enhanced response speed is attributed to increased proportion of bulk conduct resulting from the minimization of the interaction of photocarriers with oxygen molecules due to surface passivation by decorated PbS QDs, while the slightly decreased photoresponsivity is likely due to the recombination of photogenerated electrons and holes at the NWs/QDs interface and electrodes, as well as impediment of partial absorption of ZnO NWs for UV light by the PbS QDs. Flexible photodetectors on mica substrates were also constructed and underwent optoelectronic tests at bending conditions.…”

Towards Infrared Electronic Eyes: Flexible Colloidal Quantum Dot Photovoltaic Detectors Enhanced by Resonant Cavity

“…Therefore, CQDs film are flexible "solids," which can be stretched or compressed. [19][20][21][22][23] As shown in Figure 1e, the HgTe CQDs used in this study form a network of nanoparticles with absorption tuned for SWIR and MWIR (3-5 µm), covering two important infrared imaging windows. To quantitatively evaluate the performance of the flexible HgTe CQDs detectors, a group of SWIR detectors with cutoff wavelength around 2.5 µm was fabricated and characterized.…”