Optical Study of GaAs quantum dots embedded into AlGaAs nanowires

We report on the photoluminescence characterization of GaAs quantum dots embedded into AlGaAs nano-wires. Time integrated and time resolved photoluminescence measurements from both an array and a single quantum dot/nano-wire are reported. The influence of the diameter sizes distribution is evidenced in the optical spectroscopy data together with the presence of various crystalline phases in the AlGaAs nanowires.Comment: 5 page, 5 figure

MBE growth and TEM analyses in Mn-Ge-P compounds

. Pp, 81.15.Hi Ternary MnGeP 2 thin films have been grown on GaAs substrate using MBE technique. The films prepared at 435 °C showed ferromagnetism at room temperature. TEM observation revealed a segregation of MnP tile-shaped grains. Films grown at 585 °C showed no trace of ferromagnetic secondary phases in XRD profiles and were found to show no ferromagnetic behaviors down to 77 K. This is consistent with theoretical prediction that stoichiometric MnGeP 2 is antiferromagnetic, and our previous experimental results that the MnGeP 2 layer existing at the top of ZnGeP 2 : Mn has no contribution to ferromagnetic properties of the latter

Electrical detection of picosecond acoustic pulses in vertical transport devices with nanowires

Picosecond acoustic pulses, generated in a thin aluminum transducer, are injected into semiconductor vertical transport devices consisting of core-shell GaAsP nanowires. The acoustic pulses induce current pulses in the device with amplitude ∼1 μA. The spectrum of the electrical response is sensitive to the elastic properties of the device and has a frequency cutoff at ∼10 GHz. This work shows the potential of the technique for studies the elastic properties of complex semiconductor nanodevices.Peer reviewe

Influence of the strong magnetocrystalline anisotropy on the magnetocaloric properties of MnP single crystal

Manganese monophosphate MnP single crystal deserves attention due to its rich magnetic phase diagram, which is quite different depending on the direction of the applied magnetic field. Generally speaking, it has a Curie temperature around 291 K and several other magnetic arrangements at low temperatures (cone-, screw-, fan-, and ferromagnetic-type structures). This richness is due to the strong magnetocrystalline anisotropy. In this sense, the present paper makes a thorough description of the influence of this anisotropy on the magnetocaloric properties of this material. From a fundamental view we could point out, among those several magnetic arrangements, the most stable one. On the other hand, from an applied view, we could show that the magnetic entropy change around room temperature ranges from -4.7 to -3.2 J/kg K, when the magnetic field (5T) is applied along the easy and hard magnetization directions, respectively. In addition, we have shown that it is also possible to take advantage of the magnetic anisotropy for magnetocaloric applications, i.e., we have found a quite flat magnetic entropy change (with a huge relative cooling power), at a fixed value of magnetic field, only rotating the crystal by 90 degrees.771

Low temperature impurity diffusion into largeband-gap semiconductors, Extended

Abstract. Low temperature diffusion of boron and phosphorus has been performed for the first time into the monocrystalline diamond and 6H-SiC wafers through the controlled surface injection of vacancies. By varying the parameters of the surface oxide and polycrystalline silicon overlayer during the boron/phosphorus diffusion process, it was possible to obtain the planar quantum-size p + n and n + p junctions respectively in the 6H-SiC and diamond wafers as well as the 6H-SiC transistor structures. The first findings of the high temperature (77 K) quantized conductance and single-hole transistor operation are present, which identify the formation of self-assembled quantum wells inside ultra-shallow p + -and n + -diffusion profiles. These large-band-gap nanostructures are shown to cause the high electroluminescence efficiency of the diamond and 6H-SiC p-n junctions

Optically excited THz generation from ordered arrays of GaAs nanowires

THz generation under excitation by ultrashort optical pulses from ordered arrays of GaAs nanowires is reported. It was found that the efficiency of THz generation is determined by the geometrical parameters of nanostructures and has a resonant character. Furthermore, it is shown that the terahertz generation efficiency at optimum geometrical parameters of an array of semiconductor nanowires is greater than the corresponding value for bulk semiconductor p-InAs which is the most effective THz emitter.Peer reviewe