Structural and optical properties of high quality zinc-blende/wurtzite GaAs hetero-nanowires
D. Spirkoska, J. Arbiol, A. Gustafsson, S. Conesa-Boj, F. Glas, I. Zardo, M. Heigoldt, M. H. Gass, A. L. Bleloch, S. Estrade, M. Kaniber, J. Rossler, F. Peiro, … 展开作者
D. Spirkoska, J. Arbiol, A. Gustafsson, S. Conesa-Boj, F. Glas, I. Zardo, M. Heigoldt, M. H. Gass, A. L. Bleloch, S. Estrade, M. Kaniber, J. Rossler, F. Peiro, J. R. Morante, L. Samuelson, G. Abstreiter, A. Fontcuberta i Morral
The structural and optical properties of 3 different kinds of GaAs nanowires with 100% zinc-blende structure and with an average of 30% and 70% wurtzite are presented. A variety of shorter and longer segments of zinc-blende or wurtzite crystal phases are observed by transmission electron microscopy in the nanowires. Sharp photoluminescence lines are observed with emission energies tuned from 1.515 eV down to 1.43 eV when the percentage of wurtzite is increased. The downward shift of the emission peaks can be understood by carrier confinement at the interfaces, in quantum wells and in random short period superlattices existent in these nanowires, assuming a staggered band-offset between wurtzite and zinc-blende GaAs. The latter is confirmed also by time resolved measurements. The extremely local nature of these optical transitions is evidenced also by cathodoluminescence measurements. Raman spectroscopy on single wires shows different strain conditions, depending on the wurtzite content which affects also the band alignments. Finally, the occurrence of the two crystallographic phases is discussed in thermodynamic terms.
Developing a valence force field model for wurtzite semiconductors by exploiting similarities with [111]-oriented zinc blende systems: The case of wurtzite boron nitride, III-N materials and (B,In,Ga)N alloys
Self-selective growth of GaAs1-xBix on GaAs zinc blende/wurtzite nanowire heterostructures
Lund University（隆德大学）；NanoLund, Lund University（隆德大学纳米隆德）；Centre for Analysis and Synthesis, Lund University（隆德大学分析与合成中心）；MAX IV Laboratory, Lund University（隆德大学MAX IV实验室）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯玻尔研究所）
A systematic numerical investigation of spin-orbit fields in the conduction bands of III-V semiconductor nanowires is performed. Zinc-blende InSb nanowires are considered along [001], [011], and [111] directions, while wurtzite InAs nanowires are studied along [0001] and [10$\overline{1}$0] or [11$\overline{2}$0] directions. Realistic multiband $\vec{k} \cdot \vec{p}\,$ Hamiltonians are solved by using plane-wave expansions of real-space parameters. In all cases the linear and cubic spin-orbit coupling parameters are extracted for nanowire widths from 30 to 100 nm. Typical spin-orbit energies …
Electron Spin Relaxation in Two Polymorphic Structures of GaN
利用投影约化方法推导出的电子自旋弛豫时间公式，从微观角度解释了电子与压电形变声子相互作用系统中电子自旋的弛豫过程.计算了GAN两种多晶结构的电子自旋弛豫时间。通过与先前报道的实验结果进行比较，获得了纤锌矿结构的压电材料常数P_pe=1.5 x 10^29 eV/m。纤锌矿和锌掺杂GaN的弛豫时间随温度和磁场的变化规律相似，但锌掺杂GAN的弛豫时间随温度和磁场的升高而减小，且减小速度更快。本研究还表明，在低密度下，纤锌矿GAN的电子自旋弛豫可以用Elliot-Yafet过程来解释，但在金属区域中，锌掺杂GAN的电子自旋弛豫不能用Elliot-Yafet过程来解释。
Abstract Characterizing the crystalline disorder properties of the heterovalent ternary semiconductors continues to challenge solid-state theory. Here, a Landau theory is developed for the wurtzite-based ternary semiconductor ZnSnN2. It is shown that the symmetry properties of two nearly co-stable phases, with space groups Pmc21 and Pbn21, infer that a reconstructive phase transition is the source of crystal structure disorder via a mixture of the phases. The site exchange defect, which consists of two adjacent antisite defects, is identified as the nucleation mechanism of the transition. A La…
The in-plane coefficient of thermal expansion (CTE) for CdSe nanoplatelets with the zinc-blende structure containing from two to five monolayers is calculated from first principles within the quasiharmonic approximation. A comparison of the obtained results with those for bulk CdSe with both the zinc-blende and wurtzite structures finds a significant increase in the magnitude of negative CTE and the temperature range of its observation in nanoplatelets. The main contribution to the negative thermal expansion in CdSe nanoplatelets is given by the out-of-plane flexural ZA mode and in-plane optic…
Optical properties of wurtzite GaN/AlN quantum dots grown on non-polar planes: the effect of stacking faults in the reduction of the internal electric field
While the properties of wurtzite GaAs have been extensively studied during the past decade, little is known about the influence of the crystal polytype on ternary (In,Ga)As quantum well structures. We address this question with a unique combination of correlated, spatially-resolved measurement techniques on core-shell nanowires that contain extended segments of both the zincblende and wurtzite polytypes. Cathodoluminescence hyperspectral imaging reveals a blueshift of the quantum well emission energy by $75\pm15$ meV in the wurtzite polytype segment. Nanoprobe x-ray diffraction and atom probe …
Strain distribution in zincblende and wurtzite GaAs nanowires bent by a one-sided (In, Al)As stressor shell: consequences for torsion, chirality, and piezoelectricity
In this paper we show how to link the electronic structures of two III-V systems, one a direct gap material, GaAs, and the other an indirect gap material, GaP, from their bulks right down to the shape of thin nanowires. GaAs and GaP bulk and nanowire systems are studied in the zincblende and wurtzite structures both free of strain and subjected to biaxial strains perpendicular to the [111]/[0001] direction. We provide an interpretation of the band structure of nanowires, grown along the [111] (zinc-blende structure) and the [0001] (wurtzite structure) directions, in terms of the bulk band stru…
