Bias-Controlled Optical Transitions in GaN/AlN Nanowire Heterostructures.

We report on the control and modification of optical transitions in 40× GaN/AlN heterostructure superlattices embedded in GaN nanowires by an externally applied bias. The complex band profile of these multi-nanodisc heterostructures gives rise to a manifold of optical transitions, whose emission characteristic is strongly influenced by polarization-induced internal electric fields. We demonstrate that the superposition of an external axial electric field along a single contacted nanowire leads to specific modifications of each photoluminescence emission, which allows to investigate and identify their origin and to control their characteristic properties in terms of transition energy, intensity and decay time. Using this approach, direct transitions within one nanodisc, indirect transitions between adjacent nanodiscs, transitions at the top/bottom edge of the heterostructure, and the GaN near-band-edge emission can be distinguished. While the transition energy of the direct transition can be shifted by external bias over a range of 450 meV and changed in intensity by a factor of 15, the indirect transition exhibits an inverse bias dependence and is only observable and spectrally separated when external bias is applied. In addition, by tuning the band profile close to flat band conditions, the direction and magnitude of the internal electric field can be estimated, which is of high interest for the polar group III-nitrides. The direct control of emission properties over a wide range bears possible application in tunable optoelectronic devices. For more fundamental studies, single-nanowire heterostructures provide a well-defined and isolated system to investigate and control interaction processes in coupled quantum structures.

[1]  M. Eickhoff,et al.  Screening of the quantum-confined Stark effect in AlN/GaN nanowire superlattices by germanium doping , 2014, 1402.3081.

[2]  Robert A. Taylor,et al.  Enhancement of free-carrier screening due to tunneling in coupled asymmetric GaN/AlGaN quantum discs , 2006 .

[3]  C. Humphreys,et al.  Control of the oscillator strength of the exciton in a single InGaN-GaN quantum dot. , 2007, Physical Review Letters.

[4]  Christopher C. S. Chan,et al.  Reduced Stark shift in three-dimensionally confined GaN/AlGaN asymmetric multi-quantum disks , 2015 .

[5]  O. Ambacher,et al.  Two-Dimensional Electron Gas Recombination in Undoped AlGaN/GaN Heterostructures , 2004 .

[6]  J. Arbiol,et al.  Carrier confinement in GaN/Al x Ga 1-x N nanowire heterostructures (0 , 2011, 1109.3394.

[7]  Martin Eickhoff,et al.  Bias-Controlled Spectral Response in GaN/AlN Single-Nanowire Ultraviolet Photodetectors. , 2017, Nano letters.

[8]  M. Eickhoff,et al.  GaN nanodiscs embedded in nanowires as optochemical transducers , 2011, Nanotechnology.

[9]  Joy M. Barker,et al.  Optical and structural study of GaN nanowires grown by catalyst-free molecular beam epitaxy. I. Near-band-edge luminescence and strain effects , 2007 .

[10]  F. Rossi,et al.  Intrinsic electric field effects on few-particle interactions in coupled GaN quantum dots , 2004, cond-mat/0402260.

[11]  Yong Ding,et al.  Multi-quantum-well nanowire heterostructures for wavelength-controlled lasers. , 2008, Nature materials.

[12]  D. Kalita,et al.  Strong suppression of internal electric field in GaN/AlGaN multi-layer quantum dots in nanowires , 2011 .

[13]  Lawrence H. Robins,et al.  Steady-state and time-resolved photoluminescence from relaxed and strained GaN nanowires grown by catalyst-free molecular-beam epitaxy , 2008 .

[14]  Bruno Gayral,et al.  Quantum-confined Stark effect in GaN/AlN quantum dots in nanowires , 2009 .

[15]  M. Eickhoff,et al.  Electrical transport properties of Ge-doped GaN nanowires , 2015, Nanotechnology.

[16]  M. Stutzmann,et al.  Strain-Induced Band Gap Engineering in Selectively Grown GaN-(Al,Ga)N Core-Shell Nanowire Heterostructures. , 2016, Nano letters.

[17]  A. Rosenauer,et al.  STEMSIM—a New Software Tool for Simulation of STEM HAADF Z-Contrast Imaging , 2008 .

[18]  Vincenzo Grillo,et al.  Influence of the static atomic displacement on atomic resolution Z-contrast imaging , 2008 .

[19]  M. Eickhoff,et al.  Polarity assignment in ZnTe, GaAs, ZnO, and GaN-AlN nanowires from direct dumbbell analysis. , 2012, Nano letters.

[20]  Marcel Tencé,et al.  Nanometer scale spectral imaging of quantum emitters in nanowires and its correlation to their atomically resolved structure. , 2011, Nano letters.

[21]  Susanne Stemmer,et al.  Experimental quantification of annular dark-field images in scanning transmission electron microscopy. , 2008, Ultramicroscopy.

[22]  G. Abstreiter,et al.  Electrical control of interdot electron tunneling in a double InGaAs quantum-dot nanostructure. , 2011, Physical review letters.

[23]  Lester F. Eastman,et al.  Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN/GaN heterostructures , 1999 .

[24]  D. Hommel,et al.  Influence of Static Atomic Displacements on Composition Quantification of AlGaN/GaN Heterostructures from HAADF-STEM Images , 2014, Microscopy and Microanalysis.

[25]  Martin Eickhoff,et al.  Probing the internal electric field in GaN/AlGaN nanowire heterostructures. , 2014, Nano letters.

[26]  F. Julien,et al.  Photoluminescence polarization in strained GaN/AlGaN core/shell nanowires , 2012, Nanotechnology.

[27]  M. Eickhoff,et al.  Long-lived excitons in GaN/AlN nanowire heterostructures , 2014, 1412.7720.

[28]  V. L. Korenev,et al.  Optical Signatures of Coupled Quantum Dots , 2006, Science.

[29]  R. Dimitrov,et al.  Photoluminescence of Ga-face AlGaN/GaN single heterostructures , 2001 .

[30]  M. Eickhoff,et al.  UV Photosensing Characteristics of Nanowire-Based GaN/AlN Superlattices. , 2016, Nano letters.

[31]  Susanne Stemmer,et al.  Quantitative atomic resolution scanning transmission electron microscopy. , 2008, Physical review letters.

[32]  Nicolas Grandjean,et al.  Built-in electric-field effects in wurtzite AlGaN/GaN quantum wells , 1999 .

[33]  Steve Plimpton,et al.  Fast parallel algorithms for short-range molecular dynamics , 1993 .

[34]  Detlef Hommel,et al.  Composition mapping in InGaN by scanning transmission electron microscopy. , 2011, Ultramicroscopy.

[35]  M. Eickhoff,et al.  Intraband absorption in self-assembled Ge-doped GaN/AlN nanowire heterostructures. , 2014, Nano letters.

[36]  F. Rossi,et al.  Quantum information processing with semiconductor macroatoms. , 2000, Physical review letters.

[37]  B. Gayral,et al.  Quantum Dot-Like Behavior of Compositional Fluctuations in AlGaN Nanowires. , 2016, Nano letters.

[38]  Lucio Robledo,et al.  Conditional Dynamics of Interacting Quantum Dots , 2008, Science.

[39]  O. Brandt,et al.  Sub-meV linewidth of excitonic luminescence in single GaN nanowires: Direct evidence for surface excitons , 2010 .

[40]  P. Kambhampati,et al.  Get the Basics Right: Jacobian Conversion of Wavelength and Energy Scales for Quantitative Analysis of Emission Spectra , 2013 .

[41]  M. Reiche,et al.  Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes , 2000, Nature.

[42]  M. Stutzmann,et al.  Origin of energy dispersion in AlxGa1-xN/GaN nanowire quantum discs with low Al content , 2010 .

[43]  Jacques I. Pankove,et al.  Optical Processes in Semiconductors , 1971 .

[44]  Adrian Avramescu,et al.  Measurement of specimen thickness and composition in Al(x)Ga(1-x)N/GaN using high-angle annular dark field images. , 2009, Ultramicroscopy.

[45]  F. Julien,et al.  Ultraviolet photodetector based on GaN/AlN quantum disks in a single nanowire. , 2010, Nano letters.

[46]  Matthew F Chisholm,et al.  Ultrathin GaN quantum disk nanowire LEDs with sub-250 nm electroluminescence. , 2016, Nanoscale.

[47]  F. Rossi,et al.  Intrinsic exciton-exciton coupling in GaN-based quantum dots: Application to solid-state quantum computing , 2002 .