Enhancing light emission of ZnO microwire-based diodes by piezo-phototronic effect.

Light emission from semiconductors depends not only on the efficiency of carrier injection and recombination but also extraction efficiency. For ultraviolet emission from high band gap materials such as ZnO, nanowires have higher extraction efficiencies than thin films, but conventional approaches for creating a p-n diode result in low efficiency. We exploited the noncentral symmetric nature of n-type ZnO nanowire/p-type GaN substrate to create a piezoelectric potential within the nanowire by applying stress. Because of the polarization of ions in a crystal that has noncentral symmetry, a piezoelectric potential (piezopotential) is created in the crystal under stress. The piezopotential acts as a "gate" voltage to tune the charge transport and enhance carrier injection, which is called the piezo-phototronic effect. We propose that band modification traps free carriers at the interface region in a channel created by the local piezoelectric charges. The emission intensity and injection current at a fixed applied voltage have been enhanced by a factor of 17 and 4, respectively, after applying a 0.093% compressive strain and improved conversion efficiency by a factor of 4.25. This huge enhanced performance is suggested arising from an effective increase in the local "biased voltage" as a result of the band modification caused by piezopotential and the trapping of holes at the interface region in a channel created by the local piezoelectric charges near the interface. Our study can be extended from ultraviolet range to visible range for a variety of optoelectronic devices that are important for today's safe, green, and renewable energy technology.

[1]  Emil Wolf,et al.  Principles of Optics: Contents , 1999 .

[2]  S. M. Sze,et al.  Physics of semiconductor devices , 1969 .

[3]  K. Vedam,et al.  Pressure Dependence of the Refractive Indices of the Hexagonal Crystals Beryl, α -CdS, α -ZnS, and ZnO , 1969 .

[4]  M. Teich,et al.  Fundamentals of Photonics , 1991 .

[5]  Takeshi Uenoyama,et al.  Strain effect on electronic and optical properties of GaN/AlGaN quantum-well lasers , 1996 .

[6]  A. N. Smirnov,et al.  Raman and photoluminescence studies of biaxial strain in GaN epitaxial layers grown on 6H–SiC , 1997 .

[7]  Takashi Nakayama,et al.  Electronic structures of hexagonal ZnO/GaN interfaces , 2000 .

[8]  Zhong Lin Wang,et al.  Nanobelts of Semiconducting Oxides , 2001, Science.

[9]  M. Shur,et al.  Properties of advanced semiconductor materials : GaN, AlN, InN, BN, SiC, SiGe , 2001 .

[10]  Yu Huang,et al.  Indium phosphide nanowires as building blocks for nanoscale electronic and optoelectronic devices , 2001, Nature.

[11]  J. Gilman,et al.  Nanotechnology , 2001 .

[12]  Charles M. Lieber,et al.  Single-nanowire electrically driven lasers , 2003, Nature.

[13]  S. Denbaars,et al.  Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening , 2004 .

[14]  K. H. Kim,et al.  III-nitride blue and ultraviolet photonic crystal light emitting diodes , 2004 .

[15]  I. Kityk,et al.  Giant piezooptics effect in the ZnO-Er3+ crystalline films deposited on the glasses , 2004 .

[16]  David P. Norton,et al.  ZnO nanowire growth and devices , 2004 .

[17]  W. Park,et al.  Electroluminescence in n‐ZnO Nanorod Arrays Vertically Grown on p‐GaN , 2004 .

[18]  Peidong Yang,et al.  Nanowire dye-sensitized solar cells , 2005, Nature materials.

[19]  A. Waag,et al.  Pressure-dependent photoluminescence study of ZnO nanowires , 2005 .

[20]  Seong-Ju Park,et al.  p-ZnO/n-GaN heterostructure ZnO light-emitting diodes , 2005 .

[21]  Zhong Lin Wang,et al.  Piezoelectric field effect transistor and nanoforce sensor based on a single ZnO nanowire. , 2006, Nano letters.

[22]  Il-Kyu Park,et al.  UV Electroluminescence Emission from ZnO Light‐Emitting Diodes Grown by High‐Temperature Radiofrequency Sputtering , 2006 .

[23]  Federico Capasso,et al.  Broadband ZnO single-nanowire light-emitting diode. , 2006, Nano letters.

[24]  Zhong Lin Wang,et al.  Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays , 2006, Science.

[25]  C. Soci,et al.  ZnO nanowire UV photodetectors with high internal gain. , 2007, Nano letters.

[26]  Zhong Lin Wang,et al.  Piezoelectric-potential-controlled polarity-reversible Schottky diodes and switches of ZnO wires. , 2008, Nano letters.

[27]  S. Chua,et al.  Effects of oxygen on low-temperature growth and band alignment of ZnO∕GaN heterostructures , 2008 .

[28]  Jan Meiss,et al.  Flexible inorganic nanowire light-emitting diode. , 2008, Nano letters.

[29]  Federico Capasso,et al.  Scalable fabrication of nanowire photonic and electronic circuits using spin-on glass. , 2008, Nano letters.

[30]  Seong-Ju Park,et al.  Enhanced light extraction efficiency of GaN-based light-emitting diodes with ZnO nanorod arrays grown using aqueous solution , 2009 .

[31]  Qing Yang,et al.  Direct coupling of plasmonic and photonic nanowires for hybrid nanophotonic components and circuits. , 2009, Nano letters.

[32]  Yaguang Wei,et al.  Optical fiber/nanowire hybrid structures for efficient three-dimensional dye-sensitized solar cells. , 2009, Angewandte Chemie.

[33]  Shuang Cheng,et al.  a Study on Strain Affecting Electronic Structure of Wurtzite ZnO by First Principles , 2009 .

[34]  Yifan Gao,et al.  Piezoelectric potential gated field-effect transistor based on a free-standing ZnO wire. , 2009, Nano letters.

[35]  Qingliang Liao,et al.  High-performance piezoelectric gate diode of a single polar-surface dominated ZnO nanobelt , 2009, Nanotechnology.

[36]  X. Bai,et al.  Photoconducting response on bending of individual ZnO nanowires , 2009 .

[37]  Yan Zhang,et al.  Optimizing the power output of a ZnO photocell by piezopotential. , 2010, ACS nano.

[38]  Debdeep Jena,et al.  Polarization-Induced Hole Doping in Wide–Band-Gap Uniaxial Semiconductor Heterostructures , 2010, Science.

[39]  Niels Søndergaard,et al.  Photovoltaics with piezoelectric core-shell nanowires. , 2010, Nano letters.

[40]  Zachary Lochner,et al.  Ordered Nanowire Array Blue/Near‐UV Light Emitting Diodes , 2010, Advanced materials.

[41]  Strain-induced structural and direct-to-indirect band gap transition in ZnO nanotubes , 2010 .

[42]  Yong Ding,et al.  Photoconductive enhancement of single ZnO nanowire through localized Schottky effects. , 2010, Optics express.

[43]  Federico Capasso,et al.  Optically pumped nanowire lasers: invited review , 2010 .

[44]  Zhong Lin Wang,et al.  Lateral nanowire/nanobelt based nanogenerators, piezotronics and piezo-phototronics , 2010 .

[45]  Guang Zhu,et al.  Flexible high-output nanogenerator based on lateral ZnO nanowire array. , 2010, Nano letters.

[46]  Zhong Lin Wang Piezopotential gated nanowire devices: Piezotronics and piezo-phototronics , 2010 .

[47]  Zhong Lin Wang,et al.  Enhancing sensitivity of a single ZnO micro-/nanowire photodetector by piezo-phototronic effect. , 2010, ACS nano.

[48]  Young-Jun Park,et al.  Sound‐Driven Piezoelectric Nanowire‐Based Nanogenerators , 2010, Advanced materials.