Growth of GaN nanostructures with polar and semipolar orientations for the fabrication of UV LEDs

(Al,Ga)N light emitting diodes (LEDs), emitting over a large spectral range from 360 nm (GaN) down to 210 nm (AlN), have been successfully fabricated over the last decade. Clear advantages compared to the traditional mercury lamp technology (e.g. compactness, low-power operation, lifetime) have been demonstrated. However, LED efficiencies still need to be improved. The main problems are related to the structural quality and the p-type doping efficiency of (Al,Ga)N. Among the current approaches, GaN nanostructures, which confine carriers along both the growth direction and the growth plane, are seen as a solution for improving the radiative recombination efficiency by strongly reducing the impact of surrounding defects. Our approach, based on a 2D - 3D growth mode transition in molecular beam epitaxy, can lead to the spontaneous formation of GaN nanostructures on (Al,Ga)N over a broad range of Al compositions. Furthermore, the versatility of the process makes it possible to fabricate nanostructures on both (0001) oriented “polar” and (11 2 2) oriented “semipolar” materials. We show that the change in the crystal orientation has a strong impact on the morphological and optical properties of the nanostructures. The influence of growth conditions are also investigated by combining microscopy (SEM, TEM) and photoluminescence techniques. Finally, their potential as UV emitters will be discussed and the performances of GaN / (Al,Ga)N nanostructure-based LED demonstrators are presented.

[1]  Motoaki Iwaya,et al.  Improved Efficiency of 255–280 nm AlGaN-Based Light-Emitting Diodes , 2010 .

[2]  J. Brault,et al.  Comparison of carrier dynamics in GaN quantum dots and GaN quantum wells embedded in low-Al-content AlGaN waveguides , 2006 .

[3]  S. Chenot,et al.  Comparison between Polar (0001) and Semipolar (11\bar22) Nitride Blue–Green Light-Emitting Diodes Grown onc- andm-Plane Sapphire Substrates , 2009 .

[4]  Alexey Kavokin,et al.  Excitons in nitride heterostructures: From zero- to one-dimensional behavior , 2013 .

[5]  J. Brault,et al.  AlGaN-Based Light Emitting Diodes Using Self-Assembled GaN Quantum Dots for Ultraviolet Emission , 2013 .

[6]  J. Brault,et al.  Blue-light emission from GaN∕Al0.5Ga0.5N quantum dots , 2008 .

[7]  J. Massies,et al.  Group-III nitride quantum heterostructures grown by molecular beam epitaxy , 2001 .

[8]  B. Gil,et al.  The calculation of semipolar orientations for wurtzitic semiconductor heterostructures: application to nitrides and oxides , 2012 .

[9]  J. Massies,et al.  Time dependence of the photoluminescence of GaN/AlN quantum dots under high photoexcitation , 2003 .

[10]  Yasuhiko Arakawa,et al.  UV photoluminescence from size-controlled GaN quantum dots grown by MOCVD , 2002 .

[11]  Jean-Michel Gérard,et al.  InAs quantum boxes: Highly efficient radiative traps for light emitting devices on Si , 1996 .

[12]  B. Gayral,et al.  Optical properties of GaN quantum dots grown on nonpolar (11-20) SiC by molecular-beam epitaxy , 2005 .

[13]  J. Brault,et al.  Polar and semipolar GaN/Al0.5Ga0.5N nanostructures for UV light emitters , 2014 .

[14]  V. Adivarahan,et al.  Vertical Injection Thin Film Deep Ultraviolet Light Emitting Diodes with AlGaN Multiple-Quantum Wells Active Region , 2009 .

[15]  J. Brault,et al.  Linear alignment of GaN quantum dots on AlN grown on vicinal SiC substrates , 2003 .

[16]  Motoaki Iwaya,et al.  Novel UV devices on high-quality AlGaN using grooved underlying layer , 2009 .

[17]  Nicolas Grandjean,et al.  From visible to white light emission by GaN quantum dots on Si(111) substrate , 1999 .

[18]  J. Brault,et al.  Study of the growth mechanisms of GaN/(Al, Ga)N quantum dots: Correlation between structural and optical properties , 2011 .

[19]  J. Massies,et al.  Radiative lifetime of a single electron-hole pair in GaN/AlN quantum dots , 2006 .

[20]  Guy Feuillet,et al.  Growth kinetics and optical properties of self-organized GaN quantum dots , 1998 .

[21]  Xiaolong Du,et al.  InGaN/GaN multi-quantum dot light-emitting diodes , 2004 .

[22]  James S. Speck,et al.  Dislocation mediated surface morphology of GaN , 1999 .

[23]  J. Brault,et al.  Effects of capping on GaN quantum dots deposited on Al0.5Ga0.5N by molecular beam epitaxy , 2009 .

[24]  Yoshinobu Aoyagi,et al.  Self‐assembling GaN quantum dots on AlxGa1−xN surfaces using a surfactant , 1996 .

[25]  J. Brault,et al.  Tailoring the shape of GaN/AlxGa1−xN nanostructures to extend their luminescence in the visible range , 2009 .

[26]  J. Massies,et al.  In situ imaging of threading dislocation terminations at the surface of GaN(0001) epitaxially grown on Si(111) , 2000 .

[27]  S. Nakamura,et al.  Strain-induced polarization in wurtzite III-nitride semipolar layers , 2006 .

[28]  J. Brault,et al.  Ultra-violet GaN/Al0.5Ga0.5N quantum dot based light emitting diodes , 2013 .

[29]  J. Brault,et al.  GaN/Al0.5Ga0.5N (11-22) semipolar nanostructures: A way to get high luminescence efficiency in the near ultraviolet range , 2011 .

[30]  D. V. Dinh,et al.  Surface diffusion and layer morphology of ((112¯2)) GaN grown by metal-organic vapor phase epitaxy , 2012 .

[31]  Y. Taniyasu,et al.  An aluminium nitride light-emitting diode with a wavelength of 210 nanometres , 2006, Nature.

[32]  J. Brault,et al.  Carrier transfer and recombination dynamics of a long-lived and visible range emission from multi-stacked GaN/AlGaN quantum dots , 2010 .