Yellow luminescence in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi></mml:math>-type GaN epitaxial films

Chen, H. M.; Chen, Y. F.; Lee, Meng-Chieh; Feng, M. S.

doi:10.1103/physrevb.56.6942

Cited by 119 publications

(44 citation statements)

References 23 publications

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“…Therefore, we conclude that the optical excitation for both samples occurs from defects located in the bandgap at energies ranging from 2.2eV to 2.3eV. These values correlate well with the energy of the maximum of the yellow luminescence in photoluminescence (PL) measurements [9][10][11][12][13]. A recently published work on depth profiling of the yellow luminescence [14] also shows a strong increase in the ratio of yellow emission to near-band-edge emission near the interface.…”

Section: Results Of Photoconductivity Measurementssupporting

confidence: 61%

Interface Effects on the Persistent Photoconductivity in Thin GaN and AlGaN Films

Seifert

Kirfel

Munzel

et al. 1999

MRS Internet j. nitride semicond. res.

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Thin films of GaN and its alloy AlGaN are investigated with respect to their properties of the persistent photoconductivity (PPC). In this work, we show that the film-substrate interface plays an important role for the metastable electrical effect. Strongly absorbed bandgap light causes an increase of photoconductivity which is about one order of magnitude higher when the sample is illuminated from the substrate side near the interface than from the growth side. To access the interface properties at the substrate, we use temperature-dependent Hall effect measurements. The smallest PPC effect was observed for the GaN film with the best interface properties grown on SiC.

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Section: Results Of Photoconductivity Measurementssupporting

confidence: 61%

Interface Effects on the Persistent Photoconductivity in Thin GaN and AlGaN Films

Seifert

Kirfel

Munzel

et al. 1999

MRS Internet j. nitride semicond. res.

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“…The contribution of the observed defects acting as recombination centers is also relevant. Other results 12,28 indicate also that the yellow luminescence is favored by Si doping, as well as other doping impurities which substitute the nitrogen site in the lattice. The origin of the yellow luminescence is not well understood and it has been related to nitrogen vacancy V N -X complexes 29 ͑X are doping impurities͒, or to nitrogen antisite N Ga , 12 and recently to Ga-vacancy complexes V Ga -X.…”

Section: Resultsmentioning

confidence: 96%

“…In addition, in the group III-nitrides internal piezoelectric fields 9 induced by residual strain in the layer or by structural defects may perturb the electron-hole recombination dynamics 10 and thus the value of the diffusion length. Recently, reported studies [11][12][13][14][15] are dealing with the phenomenon of persistent photoconductivity ͑PPC͒ in p-GaN, n-doped GaN, and Al x Ga 1Ϫx N/GaN heterostructures. Therefore, the structural features leading to PPC must be considered in the interpretation of the diffusion length measurements.…”

Section: Introductionmentioning

confidence: 99%

Effects of phase separation and decomposition on the minority carrier diffusion length in AlxGa1−xN films

Cremades

Albrecht

Krinke

et al. 2000

Journal of Applied Physics

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Combined electron beam induced current and transmission electron microscopy ͑TEM͒ measurements have been performed on both undoped and Si-doped AlGaN epitaxial films with aluminum contents x ranging from xϭ0 to xϭ0.79, in order to correlate the electrical and structural properties of the films. The diffusion length of holes in the films ranges between 0.3 and 15.9 m, and the estimated lifetime of holes for doped samples varies between 0.2 ns and 16 s. Different effects contribute to the observed increase in the diffusion length with increasing aluminum content. Among others, dislocations seem to be active as nonradiative recombination sites, and phase separation and decomposition as observed by TEM in Al-rich alloys lead to the formation of a spatially indirect recombination path due to the piezoelectric field in the films. Potential fluctuations associated with these phase irregularities could also give rise to electron induced persistent conductivity contributing to the increase of the diffusion length. From our experimental observations, we conclude that the silicon dopants are partially activated in Al-rich alloys, and do not influence significantly the values of the diffusion length of holes in these samples.

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“…11,12 The origin of this band gap transition is still the subject of speculation. [13][14][15][16] It is most likely due to defects caused by the Si-dopant 16,17 or unintentional O. 16 In our samples the intensity of this line is strong.…”

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confidence: 91%

Field-dependent charge carrier dynamics in GaN: Excitonic effects

Lagemaat

Vanmaekelbergh

Kelly

2004

Applied Physics Letters

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The electric-field dependence of the charge-carrier dynamics in GaN was studied by measuring excitation spectra of the sub-band-gap (yellow) luminescence as a function of bias using a Schottky junction formed at the interface between the semiconductor and an electrolyte solution. At large bias, the contribution of free electrons and holes to the photoluminescence is significantly reduced due to the dead-layer effect. As a result, striking features are revealed in the spectra close to the fundamental absorption. These features are attributed to exciton decay via yellow luminescence Electrons and holes, generated by light within the depletion layer of a Schottky diode, are effectively separated by the electric field and the minority carriers are collected at the interface. Minority carriers created within a diffusion length of the inner edge of the depletion layer can also reach the junction; 1 if they are transferred across the interface one observes photocurrent in the external circuit. Only those carriers created by light with a penetration depth ͑1/␣͒ which is larger than the sum of the minority carrier diffusion length L and the thickness of the space charge layer W will recombine, either nonradiatively or radiatively. The intensity of the emitted light I PL is given by:where 0 is the absorbed photon flux and is the ratio of the rate of radiative recombination to the total recombination rate. Many systems have been shown to conform to the "dead-layer model." 2-4Among the III-V semiconductors GaN is rather exceptional in that its exciton binding energy is large ͑ജ25 meV͒. [5][6][7][8] The formation of strongly bound electronhole pairs might be expected to influence the charge-carrier dynamics within the space-charge layer of an illuminated Schottky diode. In the present work we have used photoluminescence and photocurrent measurements on the Schottky junction formed at a semiconductor/solution interface to study excitonic effects in the field-dependent dynamics of carriers in n-type GaN epitaxial layers. We report an anomalous peak in the onset of the excitation spectrum of the subband-gap luminescence indicating enhanced emission at large band bending. We argue that this effect is due to a contribution from exciton absorption which is observed because of two reasons: the large binding energy of excitons and the suppression of emission from free carriers as a result of the dead-layer effect.The GaN epitaxial layers were grown by MOCVD on sapphire substrates using a 30 nm AlN buffer layer to reduce stress. 9 The layers were co-doped with Si. The density of uncompensated donors was 6 ϫ 10 17 cm −3 . Ohmic contacts were deposited by microwave sputtering of Ti/ Al/ Ni/ Au ͑15/ 300/ 40/ 200 nm͒. The ͑0001͒ Ga-terminated surface was exposed to solution.9 A standard three electrode cell was used for the electrochemical experiments. All potentials are reported with respect to the standard calomel electrode. Reproducible clean electrode surfaces were obtained by dipping in HCl before each experiment. The electrolyte fo...

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Yellow luminescence inn-type GaN epitaxial films

Cited by 119 publications

References 23 publications

Interface Effects on the Persistent Photoconductivity in Thin GaN and AlGaN Films

Interface Effects on the Persistent Photoconductivity in Thin GaN and AlGaN Films

Effects of phase separation and decomposition on the minority carrier diffusion length in AlxGa1−xN films

Field-dependent charge carrier dynamics in GaN: Excitonic effects

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