Implementation of an indium-tin-oxide (ITO) direct-Ohmic contact structure on a GaN-based light emitting diode

Liu, Yi-Jung; Huang, Chien-Chang; Chen, Tai-You; Hsu, Chia-Wen; Liou, Jian-Kai; Tsai, Tsung-Yuan; Liu, Wen‐Chau

doi:10.1364/oe.19.014662

Cited by 22 publications

(7 citation statements)

References 15 publications

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“…It should be noted that such a discontinuous metal film could result a strong enhancement in the electric field at the metal/semiconductor interface and consequently lower the qφ B. Therefore, the improvements in the contact characteristics could also be ascribed to the formation of inhomogeneous qφ B at the metal/p-GaN interface. , In addition, the high solubility tendency of Ga in Au could be the probable reason for the comparatively better ohmic characteristics obtained with Au interlayer. , …”

Section: Resultsmentioning

confidence: 99%

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiO_x/Graphene Electrode

Chandramohan

Kang

Ryu

et al. 2013

ACS Appl. Mater. Interfaces

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This paper reports on the evaluation of the impact of introducing interlayers and postmetallization annealing on the graphene/p-GaN ohmic contact formation and performance of associated devices. Current-voltage characteristics of the graphene/p-GaN contacts with ultrathin Au, Ni, and NiO(x) interlayers were studied using transmission line model with circular contact geometry. Direct graphene/p-GaN interface was identified to be highly rectifying and postmetallization annealing improved the contact characteristics as a result of improved adhesion between the graphene and the p-GaN. Ohmic contact formation was realized when interlayer is introduced between the graphene and p-GaN followed by postmetallization annealing. Temperature-dependent I-V measurements revealed that the current transport was modified from thermionic field emission for the direct graphene/p-GaN contact to tunneling for the graphene/metal/p-GaN contacts. The tunneling mechanism results from the interfacial reactions that occur between the metal and p-GaN during the postmetallization annealing. InGaN/GaN light-emitting diodes with NiO(x)/graphene current spreading electrode offered a forward voltage of 3.16 V comparable to that of its Ni/Au counterpart, but ended up with relatively low light output power. X-ray photoelectron spectroscopy provided evidence for the occurrence of phase transformation in the graphene-encased NiO(x) during the postmetallization annealing. The observed low light output is therefore correlated to the phase change induced transmittance loss in the NiO(x)/graphene electrode. These findings provide new insights into the behavior of different interlayers under processing conditions that will be useful for the future development of opto-electronic devices with graphene-based electrodes.

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Section: Resultsmentioning

confidence: 99%

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiO_x/Graphene Electrode

Chandramohan

Kang

Ryu

et al. 2013

ACS Appl. Mater. Interfaces

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“…Indium-tin-oxide (ITO), one kind of heavily-doped transparent conductive oxides (TCOs), has been widely employed as transparent conducting electrode and direct-Ohmic contact layers in optoelectronic devices, due to its high transmittance and low resistivity in the visible [1][2][3][4][5]. More recently, ITO nanomaterials, e.g.…”

Section: Introductionmentioning

confidence: 99%

Broadband terahertz conductivity and optical transmission of indium-tin-oxide (ITO) nanomaterials

Yang¹,

Chang²,

Chen³

et al. 2013

Opt. Express

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Indium-tin-oxide (ITO) nanorods (NRs) and nanowhiskers (NWhs) were fabricated by an electron-beam glancing-angle deposition (GLAD) system. These nanomaterials are of interests as transparent conducting electrodes in various devices. Two terahertz (THz) time-domain spectrometers (TDS) with combined spectral coverage from 0.15 to 9.00 THz were used. These allow accurate determination of the optical and electrical properties of such ITO nanomaterials in the frequency range from 0.20 to 4.00 THz. Together with Fourier transform infrared spectroscopic (FTIR) measurements, we found that the THz and far-infrared transmittance of these nanomaterials can be as high as 70% up to 15 THz, as opposed to about 9% for sputtered ITO thin films. The complex conductivities of ITO NRs, NWhs as well films are well fitted by the Drude-Smith model. Taking into account that the volume filling factors of both type of nanomaterials are nearly same, mobilities, and DC conductivities of ITO NWhs are higher than those of NRs due to less severe carrier localization effects in the former. On the other hand, mobilities of sputtered ITO thin films are poorer than ITO nanomaterials because of larger concentration of dopant ions in films, which causes stronger carrier scattering. We note further that consideration of the extreme values of Re{σ} and Im{σ} as well the inflection points, which are functions of the carrier scattering time (τ) and the expectation value of cosine of the scattering angle (γ), provide additional criteria for accessing the accuracy of the extraction of electrical parameters of non-Drude-like materials using THz-TDS. Our studies so far indicate ITO NWhs with heights of ~1000 nm show outstanding transmittance and good electrical characteristics for applications such as transparent conducting electrodes of THz Devices.

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“…Indium tin oxide (ITO) is one of the most frequently investigated TCOs. It has been extensively studied as transparent electrodes in optoelectronic devices, e.g., biosensor [5], optical disk cavities in sub-wavelength size [6], solar cells [7], liquid crystal displays [8,9], and light emitting diodes (LED) [10]. On the other hand, the performance of material depends on the different nanostructure, such as nanosheets, nanobelts and nanocolumns [11].…”

Section: Introductionmentioning

confidence: 99%

THz conductivities of indium-tin-oxide nanowhiskers as a graded-refractive-index structure

Yang¹,

Chang²,

Lin³

et al. 2012

Opt. Express

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Indium-tin-oxide (ITO) nanowhiskers with attractive electrical and anti-reflection properties were prepared by the glancing-angle electron-beam evaporation technique. Structural and crystalline properties of such nanostructures were examined by scanning transmission electron microscopy and X-ray diffraction. Their frequency-dependent complex conductivities, refractive indices and absorption coefficients have been characterized with terahertz time-domain spectroscopy (THz-TDS), in which the nanowhiskers were considered as a graded-refractive-index (GRIN) structure instead of the usual thin film model. The electrical properties of ITO GRIN structures are analyzed and fitted well with Drude-Smith model in the 0.2~2.0 THz band. Our results indicate that the ITO nanowhiskers and its bottom layer atop the substrate exhibit longer carrier scattering times than ITO thin films. This signifies that ITO nanowhiskers have an excellent crystallinity with large grain size, consistent with X-ray data. Besides, we show a strong backscattering effect and fully carrier localization in the ITO nanowhiskers.

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Implementation of an indium-tin-oxide (ITO) direct-Ohmic contact structure on a GaN-based light emitting diode

Cited by 22 publications

References 15 publications

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiO_x/Graphene Electrode

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiO_x/Graphene Electrode

Broadband terahertz conductivity and optical transmission of indium-tin-oxide (ITO) nanomaterials

THz conductivities of indium-tin-oxide nanowhiskers as a graded-refractive-index structure

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Implementation of an indium-tin-oxide (ITO) direct-Ohmic contact structure on a GaN-based light emitting diode

Cited by 22 publications

References 15 publications

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiOx/Graphene Electrode

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiOx/Graphene Electrode

Broadband terahertz conductivity and optical transmission of indium-tin-oxide (ITO) nanomaterials

THz conductivities of indium-tin-oxide nanowhiskers as a graded-refractive-index structure

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Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiO_x/Graphene Electrode

Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiO_x/Graphene Electrode