Electronic structure of In1-xMnxAs studied by photoemission spectroscopy: Comparison with Ga1-xMnxAs

We have investigated the electronic structure of the p-type diluted magnetic semiconductor In1-xMnxAs by photoemission spectroscopy. The Mn 3d partial density of states is found to be basically similar to that of Ga1-xMnxAs. However, the impurity-band-like states near the top of the valence band have not been observed by angle-resolved photoemission spectroscopy unlike Ga1-xMnxAs. This difference would explain the difference in transport, magnetic and optical properties of In1-xMnxAs and Ga1-xMnxAs. The different electronic structures are attributed to the weaker Mn 3d-As 4p hybridization in In1-xMnxAs than in Ga1-xMnxAs.

Intrinsically limited critical temperatures of highly doped Ga1-xMnxAs thin films

Ga1-xMnxAs films with exceptionally high saturation magnetizations of approximate to 100 emu/cm(3) corresponding to effective Mn concentrations of x(eff)approximate to 0.10 still have a Curie temperature T-C smaller than 195 K contradicting mean-field predictions. The analysis of the critical exponent beta of the remnant magnetization-beta = 0.407(5)-in the framework of the models for disordered/amorphous ferromagnets suggests that this limit on T-C is intrinsic and due to the short range of the ferromagnetic interactions resulting from the small mean-free path of the holes. This result questions the perspective of room-temperature ferromagnetism in highly doped GaMnAs.

Raman scattering study on Ga1-xMnxAs prepared by Mn ions implantation, deposition and post-annealing

Raman scattering measurements have been performed in Ga1-xMnxAs crystals prepared by Mn ions implantation, deposition, and post-annealing. The Raman spectrum measured from the implanted surface of the sample shows some weak phonon modes in addition to GaAs-like phonon modes, where the GaAs-like LO and TO phonons are found to be shifted by approximately 4 and 2 cm(-1), respectively, in the lower frequency direction compared to those observed from the unimplanted surface of the sample. The weak vibrational modes observed are assigned to hausmannite Mn3O4 like. The coupled LO-phonon plasmon mode (CLOPM), and defects and As related vibrational modes caused by Mn ions implantation, deposition, and post-annealing are also observed. The compositional dependence of GaAs-like LO phonon frequency is developed for strained and unstrained conditions and then using the observed LOGaAs peak, the Mn composition is evaluated to be 0.034. Furthermore, by analyzing the intensity of CLOPM and unscreened LOGaAs phonon mode, the hole density is evaluated to be 1.84 x 10(18) cm(-3). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Raman scattering study on diluted magnetic semiconductor Ga1-xMnxAs prepared by Mn-ion implantation

Raman scattering measurements have been performed in diluted magnetic semiconductor Ga1-xMnxAs prepared by Mn-ion implantation, deposition, and post-annealing technique. It is found that the Raman spectrum measured from the implanted surface of the sample shows some new weak modes in addition to the GaAs-like modes which are observed from the unimplanted surface. The new vibrational modes observed are assigned to MnAs-like modes. The coupled LO-phonon plasmon mode, and Mn and As related vibrational modes caused by Mn-ion implantation, deposition, and post-annealing are also observed. Furthermore, the GaAs-like modes are found to be shifted by approximately 4 cm(-1) in the lower frequency side, compared with those observed from the unimplanted surface.

Disorder effects produced by the Mn and H incorporations on the optical absorption edge of Ga1-xMnxAs:H nanocrystalline films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Storage moduli, loss moduli and damping factor of GaAs and Ga1-xMnxAs thin films using DMA 2980

The spin injector part of spintronic FET and diodes suffers from fatigue due to rising heat on the depletion layer. In this study the stiffness of Ga1-xMnxAs spin injector in terms of storage modulus with respect to a varying temperature, 45 degrees C <= T <= 70 degrees C was determined. It was observed that the storage modulus for MDLs (Manganese Doping Levels) of 0%, 1% and 10% decreased with increase in temperature while that with MDLs of 20% and 50% increase with increase in temperature. MDLs of 20% and 50% appear not to allow for damping but MDLs <= 20% allow damping at temperature range of 45 degrees C <= T <= 70 degrees C. The magnitude of storage moduli of GaAs is smaller than that for ferromagnetic Ga1-xMnxAs systems. The loss moduli for GaAs were found to reduce with increase in temperature. Its magnitude of reducing gradient is smaller than Ga1-xMnxAs systems. The two temperature extremes show a general reduction in loss moduli for different MDLs at the study temperature range. From damping factor analysis, damping factors for ferromagnetic Ga1-xMnxAs was found to increase with decrease in MDLs contrary to GaAs which recorded the largest damping factor at 45 degrees C <= T <= 70 degrees C Hence, MDL of 20% shows little damping followed by 50% while MDL of 0% has the most damping in an increasing trend with temperature. (C) 2013 Elsevier Ltd. All rights reserved.

Electrical transport mechanisms and structure of hydrogenated and non-hydrogenated nanocrystalline Ga1-xMnxAs films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Raman scattering study of vibrational modes and hole concentration in GaxMn1-xSb

The Raman scattering study of vibrational modes and hole concentration in a ferromagnetic semiconductor Ga1-xMnxSb grown by Mn ion implantation, deposition and post-annealing has been presented. The experiments are performed both in implanted and unimplanted regions before and after etching the samples. The Raman spectra measured from the unimplanted region show only GaSb-like phonon modes. On the other hand, the spectra measured from the implanted region show additional phonon modes approximately at 115, 152, 269, 437 and 659 cm(-1). The experimental results demonstrate that the extra modes are associated with surface defects, crystal disorder and blackish layer that is formed due to Mn ion implantation, deposition and annealing processes. Furthermore, we have determined the hole concentration as a function of laser probing position by modeling the Raman spectra using coupled mode theory. The contributions of GaSb-like phonon modes and coupled LO-phonon plasmon mode are taken into consideration in the model. The hole-concentration-dependent CLOPM is resolved in the spectra measured from the implanted and nearby implanted regions. The hole concentrations determined by Raman scattering are found to be in good agreement with those measured by the electrochemical capacitance-voltage technique.

Magneto-transport and optical properties of diluted magnetic semiconductor Ga1-xMnxSb

We have studied magneto-transport and optical properties of Ga1-xMnxSb crystals (x = 0.01, 0.02, 0.03 and 0.04) grown by horizontal Bridgman method. Negative magnetoresistance and anomalous Hall effect have been observed below 10K. Temperature dependence of magnetization measurement shows a magnetic ordering below 10K which could arise from Ga1-xMnxSb alloy formation. Also, saturation in magnetization observed even at room temperature suggests the existence of ferromagnetic MnSb clusters. Reduction in band gap is observed with increasing Mn concentration in the crystals. Temperature dependence of band gap follows Bose-Einstein's model.

Search for new transparent conductors: Effect of Ge doping on the conductivity of Ga2O3, In2O3 and Ga1.4In0.6O3

Only a small amount (<= 3.5 mol%) of Ge can be doped in Ga2O3, Ga1.4In0.6O3 and In2O3 by means of solid state reactions at 1400 degrees C. All these samples are optically transparent in the visible range, but Ge-doped Ga2O3 and Ga1.4In0.6O3 are insulating. Only Ge-doped In2O3 exhibits a significant decrease in resistivity, the resistivity decreasing further on thermal quenching and H-2 reduction.The resistivity of 2.7% Ge-doped In2O3 after H-2 reduction shows a metallic behavior, and a resistivity of similar to 1 m Omega cm at room temperature, comparable to that of Sn-doped In2O3. (C) 2010 Elsevier Ltd. All rights reserved.

Ga1-xMnxSb grown on GaSb substrate by liquid phase epitaxy

The Gal(1-x)Mn(x)Sb epilayer was prepared on the n-type GaSb substrate by liquid phase epitaxy. The structure of the Gal(1-x)Mn(x)Sb epilayer was analyzed by double-crystal X-ray diffraction. From the difference of the lattice constant between the GaSb substrate and the Ga1-xMnxSb epilayer, the Mn content in the Ga1-xMnxSb epilayer were calculated as x = 0.016. The elemental composition of Ga1-xMnxSb epilayer was analyzed by energy dispersive spectrometer. The carrier concentration was obtained by Hall measurement. The hole concentration in the Ga1-xMnxSb epilayer is 4.06 x 10(19)cm(-3). It indicates that most of the Mn atoms in Ga1-xMnxSb take the site of Ga, and play a role of acceptors. The current-voltage curve of the Ga1-xMnxSb/GaSb heterostructure was measured, and the rectifying effect is obvious. (C) 2003 Elsevier B.V. All rights reserved.

GaAs-Ga1-xAlAs DH激光器空间分辨的电荧光N-NI-V特性及其对DH激光器性能的影响

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

Raman scattering characterization of Mn composition and strain in Ga1-xMnxSb/GaSb epitaxial layers

Raman scattering (RS) experiments have been performed for simultaneous determination of Mn composition and strain in Ga1-xMnxSb thin films grown on GaSb substrate by liquid phase epitaxy technique. The Raman spectra obtained from various Ga1-xMnxSb samples show only GaSb-like phonon modes whose frequency positions are found to have Mn compositional dependence. With the combination of epilayer strain model, RS and energy dispersive x-ray (EDX) experiments, the compositional dependence of GaSb-like LO phonon frequency is proposed both in strained and unstrained conditions. The proposed relationships are used to evaluate Mn composition and strain from the Ga1-xMnxSb samples. The results obtained from the RS data are found to be in good agreement with those determined independently by the EDX analysis. Furthermore, the frequency positions of MnSb-like phonon modes are suggested by reduced-mass model. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Ga1-xMnxSb grown on GaSb substrate by liquid phase epitaxy

The Gal(1-x)Mn(x)Sb epilayer was prepared on the n-type GaSb substrate by liquid phase epitaxy. The structure of the Gal(1-x)Mn(x)Sb epilayer was analyzed by double-crystal X-ray diffraction. From the difference of the lattice constant between the GaSb substrate and the Ga1-xMnxSb epilayer, the Mn content in the Ga1-xMnxSb epilayer were calculated as x = 0.016. The elemental composition of Ga1-xMnxSb epilayer was analyzed by energy dispersive spectrometer. The carrier concentration was obtained by Hall measurement. The hole concentration in the Ga1-xMnxSb epilayer is 4.06 x 10(19)cm(-3). It indicates that most of the Mn atoms in Ga1-xMnxSb take the site of Ga, and play a role of acceptors. The current-voltage curve of the Ga1-xMnxSb/GaSb heterostructure was measured, and the rectifying effect is obvious. (C) 2003 Elsevier B.V. All rights reserved.

Raman scattering study on vibrational modes in Ga1-xMnxN prepared by Mn-ion implantation

Raman scattering measurements have been carried out on ferromagnetic semiconductor Ga1-xMnxN prepared by Mn-ion implantation and post annealing. The Raman results obtained from the annealed and un-annealed Ga1-xMnxN demonstrate that crystalline quality has been improved in Ga1-xMnxN after annealing. Some new vibrational modes in addition to GaN-like modes are found in the Raman spectra measured from the Ga1-xMnxN where the GaN-like modes are found to be shifted in the higher frequency side than those measured from the bulk GaN. A new vibrational mode observed is assigned to MnN-like mode. Other new phonon modes observed are assigned to disorder-activated modes and Mn-related vibrational modes caused by Mn-ion implantation and post-annealing. (c) 2006 Elsevier Ltd. All rights reserved.