Nonpolar m-plane thin film GaN and InGaN∕GaN light-emitting diodes on LiAlO2(100) substrates

Liu, B.; Zhang, Rong; Xie, Zili; Liu, C. X.; Kong, Jizhou; Yao, Jinshan; Liu, Q. J.; Zhang, Z.; Fu, Deyi; Xiu, Xiangqian; Lu, Hai; Chen, P.; Han, Ping; Gu, Shulin; Shi, Yi; Zheng, Yi; Zhou, Jingzhe; Zhou, Shengming

doi:10.1063/1.2825419

Cited by 45 publications

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References 21 publications

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“…It also exhibits some collinear features in the GaN epilayer probed by atomic force microscopy. 4 Both anisotropic crystallography and surface morphology are quite similar to the behavior of nonpolar GaN grown on different substrates. 5,8,16 This result implies different mosaic block dimensions along the two orthogonal directions, parallel and perpendicular to the ͓0001͔ direction of m-plane GaN.…”

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confidence: 52%

“…Consequently, it results in reduction of quantum efficiency of light-emitting diodes. 2 A way to overcome this deficiency is to grow GaNbased QWs along nonpolar orientations, for example, m plane 3,4 or a plane. 5,6 It has been shown that the electric field can be avoided in such nitride QWs.…”

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confidence: 99%

“…Following a GaN cover layer for protecting LAO substrates, the main GaN layer was grown at 1050°C. 4 The only difference of process is the growth temperature of the cover layer GaN; one is 800°C ͑S1͒, the other one is 850°C ͑S2͒. The thickness of both GaN films is about 0.9 m. The samples were mounted on the goniometer of a PANalytical X'Pert-Pro MRD for analyzing the structure properties of m-plane GaN.…”

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Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)

Liu

Zhang

Xie

et al. 2008

Applied Physics Letters

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The m-plane GaN films grown on LiAlO 2 ͑100͒ by metal-organic chemical vapor deposition exhibit anisotropic crystallographic properties. The Williamson-Hall plots point out they are due to the different tilts and lateral correlation lengths of mosaic blocks parallel and perpendicular to GaN͓0001͔ in the growth plane. The symmetric and asymmetric reciprocal space maps reveal the strain of m-plane GaN to be biaxial in-plane compress xx = −0.79% and zz = −0.14% with an out-of-plane dilatation yy = 0.38%. This anisotropic strain further separates the energy levels of top valence band at ⌫ point. The energy splitting as 37 meV as well as in-plane polarization anisotropy for transitions are found by the polarized photoluminescence spectra at room temperature. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2951618͔The wurtzite structure of III-nitrides leads to electrostatic fields along the ͓0001͔ direction due to spontaneous and piezoelectric polarization, when the film is grown on c-oriented substrates. 1 These built-in electric fields along the ͓0001͔ direction separate the electron and hole wave functions in a quantum well ͑QW͒ thereby reducing the recombination probability of electron-hole pairs. Consequently, it results in reduction of quantum efficiency of light-emitting diodes. 2 A way to overcome this deficiency is to grow GaNbased QWs along nonpolar orientations, for example, m plane 3,4 or a plane. 5,6 It has been shown that the electric field can be avoided in such nitride QWs. When ͓1100͔ or ͓1120͔ becomes the growth direction, the c axis of GaN lattice lies down in the growth plane. As a consequence, the C 6v hexagonal symmetry of the c growth plane is reduced to C 2v symmetry of the m growth plane. Firstly, it would show the anisotropic crystallographic characteristics. 7,8 Secondly, the nonpolar GaN films experience strong anisotropic deformation due to different in-plane lattice mismatches and thermalexpansion coefficients between GaN and underlying substrates. In the case of c-plane GaN films, isotropic strain in the c-plane preserves C 6v symmetry in the x-y plane so that no significant in-plane physical anisotropy occurs. The situation is quite different for nonpolar GaN films. Anisotropic in-plane strain components further lift the symmetry in the growth plane, which significantly modify the top three valence band ͑VB͒ states at ⌫ point. 9,10 Both the energy splitting and polarization selection of the transitions between conduction band ͑CB͒ and VB have been observed by absorption, reflectance, and photoreflectance spectroscopy. 11,12 Recently, transmission anisotropy spectroscopy has been utilized to obtain the energy splitting and polarization information of m-plane GaN films. 13 Although the in-plane strain components are important for the modifications in band structure of nonpolar GaN, it is still difficult to experimentally determine the full state of strain. In the case of m plane, GaN films are grown along GaN ͓1100͔ direction. The growth plane is the x-z plane, and the growth direc...

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Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)

Liu

Zhang

Xie

et al. 2008

Applied Physics Letters

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“…The m-plane InGaN/GaN multiple quantum wells (MQWs) have been synthesized substrates by molecular-beam epitaxy(MBE) 4 and LED structures have been grown by metal-organic chemical vapor deposition (MOCVD) on LiAlO 2 [LAO] (100) 5,6 , recently. This non-polar plane GaN will exhibit intrinsic in-plane anisotropy even in the unstrained case due to the broken hexagonal symmetry.…”

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Non-polar m-plane GaN film and polarized InGaN/GaN LED grown on LiAlO 2 (001) substrates

et al. 2010

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The non-polar m-plane GaN film and polarized InGaN/GaN light-emitting diode (LED) grown by metal-organic chemical vapor deposition (MOCVD) on LiAlO 2 (100) substrates were investigated. Firstly, the simulation of excitonic transition energies and polarization effects on band structure of non-polar plane GaN was studied using the k· p Hamiltonian approach. Due to small lattice mismatch between GaN and LiAlO 2 substrate, X-ray diffraction (XRD) revealed that the obtained m-plane GaN film has only ] 00 1 1 [ orientation with single-crystalline quality. In addition, anisotropic crystallographic properties and strain were found, which originates from the broken hexagonal symmetry. The anisotropic strain further separates the energy levels of top valence band at Γ point. The energy splitting as 37meV as well as in-plane polarization anisotropy for transitions are found by the polarized photoluminescence spectra at room temperature, which is consistent with our simulation. The fabricated InGaN/GaN LED on LiAlO 2 (100) emits green polarized light at room temperature. And the polarization degree of the emission reaches up to 60% at the wavelength of 520nm.

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“…4 High-resolution x-ray diffraction technique revealed the m-plane GaN epilayer under biaxial compressive strain of xx = −0.79% and zz = −0.14% with an out-of-plane dilatation yy = 0.38%. 15 An unintentionally doped n-type c-plane GaN with thickness of 2.5 m on ␣-Al 2 O 3 ͑0001͒ substrate ͑named as sample II͒ was used to compare the luminescence properties of m-plane GaN film.…”

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Polarization and temperature dependence of photoluminescence of m-plane GaN grown on γ-LiAlO2 (100) substrate

Liu

Kong

Zhang

et al. 2009

Applied Physics Letters

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We investigated the polarization and temperature dependence of photoluminescence ͑PL͒ of m-plane GaN grown on ␥-LiAlO 2 ͑100͒ substrate. The calculated electronic band structure with k • p Hamiltonian points out the energy splitting as well as polarization selection originate from the m-plane GaN epilayer under anisotropic strain. The polarization-angle dependence PL spectra are found to be selected from in-plane x-and z-polarized emission, corresponding to T 1 and T 2 transition. And the intensity distribution of the fitting peaks satisfies the Malus' law. An S-shape energy evolution of near band edge peak on temperatures is observed, which originates from the transition between the localized holes and electrons in triangular potentials induced by basal stacking faults. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3204453͔ Spontaneous and piezoelectric polarization along the ͓0001͔ axis of wurtzite GaN and its alloys greatly affect the efficiency of luminescence in GaN-based optoelectronic devices. 1 In order to eliminate these polarization effects, one way is to deposit an m-or a-plane GaN film along unconventional non-polar directions, such as ͓1100͔ ͑Ref. 2-4͒ or ͓1120͔. 5-7 ␥-LiAlO 2 ͑LAO͒ has a tetragonal structure and its ͑100͒ plane exhibits a comparatively small lattice mismatch to GaN ͑1100͒. Since the m-plane GaN was grown by molecular-beam epitaxy on this substrate, 2 the development of nonpolar GaN based optoelectronic devices has attracted much attention. Unlike c-plane GaN, nonpolar GaN usually suffers from anisotropic in-plane strain, which leads to a splitting in the electronic band structure ͑EBS͒. Therefore, understanding the EBS of nonpolar GaN is significant for the application of optoelectronic devices. Previously, optical measurements, such as reflectance, transmission, and photoreflectance, were used to determine the EBS near the ⌫ point and verify the theoretical calculation of the energy splitting of the m-plane GaN. [8][9][10][11] Luminescence properties of a-plane GaN, including temperature and polarization dependent, spatially resolved photoluminescence ͑PL͒ and cathodoluminescence, were also particularly studied. [12][13][14] Recently, the authors reported the splitting and anisotropy of emission light polarization of the m-plane GaN on LAO͑100͒ by using PL measurements. 15 In this letter, we investigate the polarization-angle and temperature dependence of the polarized PL transitions of the m-plane GaN film on LAO͑100͒ in order to explore the evolution of splitting valence band under anisotropic strain conditions.The studied sample of a typical 0.92 m thick m-plane GaN with background electron concentration ϳ2 ϫ 10 18 cm −3 ͑named as sample I͒ was grown on LAO͑100͒ by metalorganic chemical vapor deposition. 4 High-resolution x-ray diffraction technique revealed the m-plane GaN epilayer under biaxial compressive strain of xx = −0.79% and zz = −0.14% with an out-of-plane dilatation yy = 0.38%. 15 An unintentionally doped n-type c-plane GaN with thickness of 2.5 m on ␣-Al 2 O...

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Nonpolar m-plane thin film GaN and InGaN∕GaN light-emitting diodes on LiAlO2(100) substrates

Cited by 45 publications

References 21 publications

Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)

Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)

Non-polar m-plane GaN film and polarized InGaN/GaN LED grown on LiAlO 2 (001) substrates

Polarization and temperature dependence of photoluminescence of m-plane GaN grown on γ-LiAlO2 (100) substrate

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