In recent years, two distinct engineering challenges have been identified for Low Noise Amplifiers (LNAs) utilised in radio astronomy front-end receivers. There has been a sharp increase in the number of receiving elements being used in observatories, and an increased desire to utilise LNAs further into the millimeter/submillimeter region. These ch...
We performed a detailed investigation of the oxidation of the technologically relevant GaAs(001)-beta 2(2x4) surface via density functional calculations. The purpose is to gain insights on the atomistic mechanisms and local bondings that underlie the degradation of the surface properties once exposed to oxygen. The study comprises the adsorption of...
Synchrotron white beam X-ray topography has been used to characterise bulk crystal defects of thick vapour grown CdZnTe crystals. Whole 50 mm diameter wafers with thicknesses in the range of 2-3 mm were sliced from boules grown by the multi-tube physical vapour transport method and analysed by diffraction topography in a transmission geometry. A va...
In this work, we report the selective area epitaxial growth of high quality InP in shallow trench isolation (STI) structures on Si (0 0 1) substrates 6° miscut toward (1 1 1) using a thin Ge buffer layer. We studied the impact of growth rates and steric hindrance effects on the nano-twin formation at the STI side walls. It was found that a too high...
We report the selective area growth of InP layers in submicron trenches on Si (001) substrates by using a thin Ge buffer layer. The antiphase domain boundaries in InP layers are suppressed by engineering the local Ge surface profile. The mechanism of atomic step formation and the corresponding method for step density control are presented. We discu...
The GaAs based InGaAs metamorphic structures and their growth by molecular beam epitaxy(MBE) are investigated. The controlling of the source temperature is improved to realize the linearly graded InGaAs metamorphic structure precisely. The threading dislocations are reduced. We also optimize the growth and annealing parameters of the InGaAs quantum...
Molecular beam epitaxy growth of an InxGa1-xAs/GaAs quantum well(QW) structure(x equals to0.17 or0.3) on offcut(100) Ge substrate has been investigated. The samples were characterized by atomic force microscopy, photoluminescence(PL), and high resolution transmission electron microscopy. High temperature annealing of the Ge substrate is necessary t...
We demonstrate by magneto-transport measurements that a Curie temperature as high as 200 K can be obtained in nanostructures of (Ga,Mn)As. Heavily Mn-doped (Ga,Mn)As films were patterned into nanowires and then subject to low-temperature annealing. Resistance and Hall effect measurements demonstrated a consistent increase of T(C) with decreasing wi...
