Investigation of Fermi level pinning at semipolar (11–22) p-type GaN surfaces

Choi, Young Yun; Kim, Seong-Jun; Oh, Min Seok; Kim, Hyunsoo; Seong, Tae Yeon

doi:10.1016/j.spmi.2014.10.031

Cited by 14 publications

(8 citation statements)

References 32 publications

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“…This behavior means that the ideal I-V method cannot be adopted to interpret the current transport behavior of the n-AlInP Schottky contacts. 29,30 Such characteristics were associated with the inhomogeneity of barrier heights. 28 In the inhomogeneity model, a Gaussian distribution of the effective barrier heights with standard deviation (σ) and a mean Φ B,m is assumed as, 29 σ…”

Section: Methodsmentioning

confidence: 99%

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Inhomogeneous Barrier Height Characteristics of n-Type AlInP for Red AlGaInP-Based Light-Emitting Diodes

Cha¹,

Lee²,

Sim³

et al. 2022

ECS J. Solid State Sci. Technol.

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For micro-light-emitting diode (LED)-based display applications, such as virtual reality and augmented reality, high-performance Ohmic contacts (namely, the improvement of current injection efficiency) is vital to the realization of high-efficiency micro-LEDs. The surface Fermi level pinning characteristics could be comprehended in terms of the relation between work function of metals (ΦM) and Schottky barrier height (SBH, ΦB). In this study, we have investigated the surface Fermi level pinning characteristics of (001) n-AlInP surfaces by employing Schottky diodes with different metals. With an increase in the temperature, ΦB increases linearly and ideality factors (n) decreases. This behavior is related to the barrier height inhomogeneity. Inhomogeneity-model-based ΦB is evaluated to be in the range of 0.86 – 1.30 eV, which is dependent on the metal work functions and are similar to those measured from capacitance-voltage relation. Further, The S-parameter, the relation between B and M (dB/dM), is 0.36. This is indicative of the partial pinning of the surface Fermi level at the surface states placed at 0.95 eV below the conduction band. Furthermore, it is also shown that (NH4)2S-passivation results in an increases the mean SBH and the S-parameter (e.g., 0.52).

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Section: Methodsmentioning

confidence: 99%

“…29,30 Such characteristics were associated with the inhomogeneity of barrier heights. 28 In the inhomogeneity model, a Gaussian distribution of the effective barrier heights with standard deviation (σ) and a mean Φ B,m is assumed as, 29 σ…”

Section: Methodsmentioning

confidence: 99%

Inhomogeneous Barrier Height Characteristics of n-Type AlInP for Red AlGaInP-Based Light-Emitting Diodes

Cha¹,

Lee²,

Sim³

et al. 2022

ECS J. Solid State Sci. Technol.

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“…Several groups have proposed p‐type contacts based on metals like Pd, Au, Ag, Pt, Ni, and alloys like Ni/Au , Pt/Au , Pd/Au , Ag/Pd , Pd/Ir/Au , or Pd/Ni/Au and have achieved specific contact resistivity as low as 10 −6 Ω cm 2 and attributed this low specific contact resistivity to one or more factors like surface preparation, metal deposition technique, annealing technique , and increase of holes due to acceptor like Ga vacancy creation . However, regarding carrier transport mechanism in p‐contact with low specific contact resistivity, differing theories have been proposed such as trap‐assisted tunnelling enhanced by nitrogen vacancy related defects , tunnelling of carriers through Schottky barrier , thermionic emission (TE) , thermionic field emission (TFE) or carrier transport through deep level defect (DLD) band . Therefore, it is still important to study the p‐GaN layer and the optimization of p‐contact metallization process particularly for In rich InGaN alloy structures and to understand the carrier transport through the metallic contacts.…”

Section: Introductionmentioning

confidence: 99%

Investigation of p-contact performance for indium rich InGaN based light emitting diodes and solar cells

Alam

Haas

et al. 2016

Phys. Status Solidi A

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We report on the optimization of p-GaN layers for high indium (In) content InGaN applications by optimizing temperature, precursor CP 2 Mg flow rate and III/V ratio and report also on the optimization of p-contact performance. Using MOVPE, a 150 nm thick p-type GaN with moderate Mg doping and a 50 nm contact layer with high Mg doping concentration were grown on standard GaN templates at growth temperatures in the range of 850-1000 8C. Hall measurement yields hole concentration of 4.8 Â 10 17 cm À3 for the optimized sample. SIMS shows Mg concentration of 1.7 Â 10 20 cm À3 on average in the heavily doped and 4 Â 10 19 cm À3 on average in the moderately doped p-GaN layer for the optimized p-GaN. A multilayer Pd/Ag/Ni/Au metal contact has been deposited on this p-GaN and studied using the CTLM technique. Optimization of both p-GaN layers and p-contact processing led to a low resistance contact with specific contact resistivity of 6 Â 10 À4 Ω cm 2 . We believe, the very high Mg concentration of the surface layer in intimate contact with the contact metal reduces the Schottky barrier height and band bending. This optimization of p-GaN is an important step towards high efficiency green LEDs and solar cells.

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“…The reported Schottky barrier heights range from 0.5 to 2.9 eV. [7−14] However, the results from Choi et al [15] and Rickert et al [10] indicate that the surface Fermi level of the p-GaN is pinned perfectly because of high-density deep level defects, which is essentially independent of the metal work function. Choi et al [15] proposed that the 𝑆-parameter of the semi-polar p-GaN Schottky diode (SD) that contains different Schottky metal contacts was nearly zero, which indicates a perfectly pinned Fermi level and a high density of deep-level defects due to vacancy-related or Mg-induced defects on the p-GaN surface.…”

mentioning

confidence: 99%

“…[7−14] However, the results from Choi et al [15] and Rickert et al [10] indicate that the surface Fermi level of the p-GaN is pinned perfectly because of high-density deep level defects, which is essentially independent of the metal work function. Choi et al [15] proposed that the 𝑆-parameter of the semi-polar p-GaN Schottky diode (SD) that contains different Schottky metal contacts was nearly zero, which indicates a perfectly pinned Fermi level and a high density of deep-level defects due to vacancy-related or Mg-induced defects on the p-GaN surface. Nguyen et al [16] studied the admittance results for Ni/Au/p-GaN Schottky structures theoretically and experimentally, using thermaladmittance spectroscopy measurements from 90 K to 300 K. The electrical characteristics and the basic parameters for the metal-semiconductor junction were explained.…”

mentioning

confidence: 99%

Characterization of Interface State Density of Ni/p-GaN Structures by Capacitance/Conductance-Voltage-Frequency Measurements

Zhu¹,

Zhang²,

Liang³

et al. 2017

Chinese Phys. Lett.

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For the frequency range of 1 kHz–10 MHz, the interface state density of Ni contacts on p-GaN is studied using capacitance-voltage (C–V) and conductance-frequency-voltage (G–f–V) measurements at room temperature. To obtain the real capacitance and interface state density of the Ni/p-GaN structures, the effects of the series resistance () on high-frequency (5 MHz) capacitance values measured at a reverse and a forward bias are investigated. The mean interface state densities obtained from the – capacitance and the conductance method are and , respectively. Furthermore, the interface state density derived from the conductance method is higher than that reported from the Ni/n-GaN in the literature, which is ascribed to a poor crystal quality and to a large defect density of the Mg-doped p-GaN.

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Investigation of Fermi level pinning at semipolar (11–22) p-type GaN surfaces

Cited by 14 publications

References 32 publications

Inhomogeneous Barrier Height Characteristics of n-Type AlInP for Red AlGaInP-Based Light-Emitting Diodes

Inhomogeneous Barrier Height Characteristics of n-Type AlInP for Red AlGaInP-Based Light-Emitting Diodes

Investigation of p-contact performance for indium rich InGaN based light emitting diodes and solar cells

Characterization of Interface State Density of Ni/p-GaN Structures by Capacitance/Conductance-Voltage-Frequency Measurements

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