SPIN-ORBIT ENHANCED POLARON IN A SINGLE QUANTUM WELL

The polaronic corrections to the electron energy and effective mass are calculated taking the Rashba spin-orbit coupling in the compositionally asymmetric single quantum well based on heterostructures of narrow gap semiconductors InGaAs and InAs . The electron interaction with the confined longitudinal optic phonon is considered in the Fröhlich form for calculating the polaron properties. In the weak coupling limit, the polaron properties are enhanced by the Rashba spin-orbit coupling in the asymmetric quantum well.

Raman Characterization of Doped 3C-SiC/Si for Different Silicon Substrates and C/Si Ratios

Raman microscopy has been used to study transport properties in hetero-epitaxial 3C-SiC/Si thin films. By an accurate analysis of the Longitudinal Optic phonon-plasmon coupled (LOPC) modes in n-type doped 3C-SiC films, free carrier density and mobility has been determined. A study of doped 3C-SiC reveals a strong relationship between the calculated free carrier density and both the C/Si ratio used during the epitaxial process and Silicon substrates orientation on which 3C-SiC thin films were grown (maintaining the N2 gas flow rate). The free carrier density obtained is in the range between 5x1016 cm-3 and 4x1018 cm-3. Epitaxial films grown on (111) Si substrates show a higher free carrier density and a lower dependence on C/Si ratios as compared to films grown on (100) Si substrates.

Cathodoluminescence and microRaman study of GaN ELO structures

ABSTRACTEpitaxial Lateral Overgrowth (ELO) is an effective method to reduce dislocations in heterostructures with large lattice mismatch. This method has been widely used to improve the quality of GaN layers. We present herein a study of the properties of ELO GaN layers grown by HVPE from an MOVPE GaN buffer layer. Cathodoluminescence shows a strong enhancement of the luminescence emission in the ELO regions, where TEM has proven the absence of dislocations. Local cathodoluminescence spectra show that this enhancement is mostly due to the yellow luminescence band. Besides Donor-Acceptor Pair recombination bands are observed in the near band gap spectral range. Raman data show that the ELO layers present a good crystalline quality. The Raman spectra did not reveal the presence of free carriers in concentration high enough to allow the presence of Longitudinal Optic Phonon Plasmon Coupled modes. The results are discussed in terms of the incorporation of impurities in the ELO layers together with the formation of compensating deep acceptors, probably VGa.

Microraman Characterization Of Microdefects In Bulk Sic

MicroRaman spectroscopy is used for characterizing defects in large SiC crystals with micrometer spatial resolution. The ability to identify microscopic inclusions of polytypes different than the crystal matrix is demonstrated; silicon and carbon inclusions and disorder effects are found in micropipes. A study of the Longitudinal Optic Phonon Plasmon Coupled (LOPC) Raman modes allowed to obtain local fluctuations of the net donor concentration, ND-NA, and the electron mobility around defects, which allowed impurity gettering effects to be observed.