Series Of Ga1 Research Articles

Chemical and Mechanical Pressure-Induced Photoluminescence Tuning via Structural Evolution and Hydrostatic Pressure

A chemical and mechanical pressure-induced photoluminescence tuning method was developed through the structural evolution and hydrostatic pressure involving phase transition. A series of Ga1.98–xAl...

Scaling of the anomalous Hall effect in low Mn concentration (Ga,Mn)As

We present magnetotransport in a series of Ga1−xMnxAs (x∼0.014) films. Both ordinary and anomalous Hall resistivities are analyzed in high magnetic field (up to 18.0T) at various temperatures. The unique scaling behavior n∼0.5 is found for the entire series, which is not compatible with existing scattering theories.

Properties of Ga1−xMnxAs with high Mn composition (x>0.1)

A series of Ga1−xMnxAs layers with high Mn compositions x (=0.075–0.200) has been grown and investigated. Magnetization, magnetotransport, and magneto-optical properties reveal that the layers have single ferromagnetic phase as in the case of typical (Ga,Mn)As. The authors also describe the variation of magnetic anisotropy with x and the effect of low temperature annealing on Curie temperature.

Coherent Optical Phonon Oscillations in GaMnAs

Coherent phonon oscillations are investigated in a series of Ga1−xMnxAs layers with different Mn and hole concentrations. The longitudinal optical (LO)-phonon-hole-plasmon coupled mode oscillations are observed in layers with large Mn concentrations. The energies of these coupled modes depend on the hole concentrations, which may prove useful for determining this parameter in ferromagnetic alloys. Finally, electron-plasmon coupling with LO phonon, observed under optical excitation, is compared in GaMnAs and in LT-GaAs.

Observation of Combined Ferromagnetic/Paramagnetic Phase in Ga1?xMnxAs by Magnetic Circular Dichroism

Magnetic properties of a series of Ga1−xMnxAs layers with different Mn and hole concentrations has been studied by measuring magneto-absorption and magnetic circular dichroism (MCD). We first focus on comparing the MCD spectra of samples with unambiguous ferromagnetic or paramagnetic magnetization. We then investigate MCD in a sample with parameters between these two extremes, and interpret the observed behavior in terms of the coexistence of ferromagnetic domains and paramagnetic regions that may result, for example, from inhomogeneities in the sample caused, e.g., by compositional or doping fluctuations.

Effect of Be doping on the properties of GaMnAs ferromagnetic semiconductors

We have studied two series of molecular beam epitaxy grown Ga1−xMnxAs epilayers with several different Be doping levels. Two Mn concentrations x were chosen for this study: 0.03 and 0.05, and these values were maintained constant in each series. These samples were characterized by using SQUID and magnetotransport measurements. A systematic increase of the Curie temperature TC was observed in SQUID measurements on the series of Ga1−xMnxAs with x=0.03. The resistivity measured at zero magnetic field shows a local maximum near the Curie temperature, reflecting the effects of critical scattering near TC. The observed increase of TC in Ga1−xMnxAs for this low range of x can be explained by the increase of the free carrier concentrations in the system arising from Be doping. However, in the series of Ga1−xMnxAs with the higher concentration of Mn (x=0.05), the measurements reveal that the TC systematically decreases with increasing Be doping level. We discuss this effect in terms of a fundamental limitation of the carrier concentration that can be thermodynamically accommodated by Ga1−xMnxAs epilayers.