Jun 30, 2017

Ferromagnetism at room temperature of c- and m-plane GaN : Gd films grown on different substrates by reactive molecular beam epitaxy


We report the magnetic properties of c- and m-plane GaN : Gd films grown on different substrate materials. Additionally, we have investigated the magnetic behaviour of the bare substrates in order to analyse their possible contribution on the properties of this material system. For the growth of c-phase GaN : Gd we have used 6H–SiC(0 0 0 1) and GaN/Al2O3 templates. Whereas templates only exhibit a diamagnetic behaviour, the SiC substrates show clear signatures of ferromagnetism at room temperature. Rutherford backscattering spectroscopy and secondary ions mass spectrometry have revealed traces of Fe in the SiC substrates. This Fe contamination seems to be related to the ferromagnetic ordering observed in these substrates. LiAlO2(0 0 1) is a good choice for growth of m-plane diluted nitrides due to its diamagnetic behaviour. The hysteresis loops of c- and m-phase GaN : Gd deposited on template and LiAlO2, respectively, show coercivity and magnetic saturation. These characteristics together with the magnetization curves are indications of an intrinsic ferromagnetic behaviour in the GaN : Gd.
Source: iopscience
For more information, please visit our website:www.powerwaywafer.com, send us email atsales@powerwaywafer.com  or powerwaymaterial@gmail.com.

Radiative defect state identification in semi-insulating GaAs using photo-carrier Radiometry


The photo-carrier radiometry (PCR) technique has been applied to a semi-insulating GaAs wafer for the detection and identification of radiative defects. Due to the ultrafast free carrier recombination lifetime, the conventional carrier-diffusion-wave-based PCR theory was modified to reflect the signal domination by trap emission and capture rates in the absence of diffusion. Defect photoluminescence with photon energies from 0.7 to 1.24 eV was collected and analyzed using photo-thermal temperature spectra and resonant (rate-window) detection combined with frequency scans. Five defect levels were identified self-consistently from the combined rate-window and PCR phase data, and the temperature dependence of the defect photoluminescence quantum efficiency was determined through multi-parameter best fits of the PCR rate theory to the experimental data.
Source: Iopscience
If you need more information about GaAs wafer,please visit our website: www.powerwaywafer.com or send us email to powerwaymaterial@gmail.com

Jun 27, 2017

Optical Mapping of the Total EL2-Concentration in Semi-Insulating GaAs-Wafers

In semi-insulating GaAs wafers the distribution of the total EL2, independent of its charge state, was determined by purely optical absorption measurements. In all (Czochralski-grown) wafers studied the radial distribution of the total EL2 is W-shaped and shows fourfold symmetry. So the fluctuations of the neutral EL2-concentration seen in the usual near infrared transmission mapping reflect essentially the inhomogeneity of the total EL2 distribution. The mean EL2+ concentration in all wafers was close to typical C- and Zn-concentrations in s.i. GaAs (≈ 2centerdot1015 cm-3).

Keywords:GaAs wafers; EL2;radial distribution;EL2-concentration;


If you need more information about GaAs wafer, please visit our website: http://www.powerwaywafer.com or send us email to  powerwaymaterial@gmail.com.