Polarization induced hole doping in graded AlxGa1−xN (x = 0.7 ∼ 1) layer grown by molecular beam epitaxy

Li, Shibin; Zhang, Ting; Wu, Jiang; Yang, Yajie; Wang, Zhiming; Wu, Zhiming; Chen, Zhi; Jiang, Yadong

doi:10.1063/1.4792685

Cited by 81 publications

(56 citation statements)

References 18 publications

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“…Therefore, epitaxial growth along non-polar crystal directions, such as [1 1 00] direction, is widely studied [21]. One advantage of the polarization is that the electric field can be utilized for creating polarization induced electron or hole gas [22,23] that can be used to overcome the difficulty in obtaining highly conductive AlGaN. A doping free ("polarization doped") AlGaN-based LED was recently demonstrated [24].…”

Section: Polarizationmentioning

confidence: 99%

Doping of high-Al-content AlGaN grown by MOCVD

Nilsson¹

2014

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The high-Al-content Al x Ga 1-x N, x > 0.70, is the principal wide-band-gap alloy system to enable the development of light-emitting diodes operating at the short wavelengths in the deep-ultraviolet, λ < 280 nm. The development of the deep-ultraviolet light-emitting diodes (DUV LEDs) is driven by the social and market impact expected from their implementation in portable units for water/surface disinfection and based on the damaging effect of the deep-ultraviolet radiation on the DNA of various microorganisms. Internationally, intense research and technology developments occur in the past few years, yet, the external quantum efficiency of the DUV LEDs is typically below 1%.One of the main material issues in the development of the DUV LEDs is the achievement of n-and ptype high-Al-content Al x Ga 1-x N layers with low resistivity, which is required for the electrical pumping of the diodes. The doping process becomes significantly more complex with increasing the Al content and the electrical resistivity is as high as 10 1 -10 2 Ω . cm for n-type AlN doped by silicon, and 10 7 -10 8 Ω cm for p-type AlN doped by magnesium.The present study was therefore focused on gaining a better understanding of the constraints in the doping process of the high-Al-content Al x Ga 1-x N alloys, involving mainly silicon. For this purpose, the epitaxial growth of the high-Al-content Al x Ga 1-x N and AlN by implementing the distinct hot-wall MOCVD was developed in order to achieve layers of good structural and morphological properties, and with low content of residual impurities, particularly oxygen and carbon. Substitutional point defects O N and C N may have a profound impact on the doping by their involvement in effects of ntype carrier compensation. The process temperature was varied between 1000 and up to 1400 °C, which is a principal advantage in order to optimize the material properties of the high-Al-content Al x Ga 1-x N and AlN. The epitaxial growth of the high-Al-content Al x Ga 1-x N and AlN was largely performed on 4H-SiC substrates motivated by (i) the lattice mismatch of ~ 1% along the basal plane (the smallest among other available substrates including Si and sapphire), (ii) the good thermal conductivity of 3.7 W cm -1 K -1 , which is essential to minimize the self-heating during the operation of any light-emitting diode, and (iii) the limited access to true-bulk AlN wafers. The outcome of this study is accordingly summarized and presents our understanding for (i) the complex impact of silicon and oxygen on the n-type conductivity of Al 0.77 Ga 0.23 N, representative for the alloy composition at which a drastic reduction of the n-type conductivity of Al x Ga 1-x N is commonly reported (paper 1); (ii) the strain and morphology compliance during the intentional iv doping by silicon and magnesium, and its correlation with the resistivity of highly doped layers of Al 0.82 Ga 0.18 N alloy composition (paper2); (iii) the n-type conductivity of highly Si-doped Al 0.72 Ga 0.28 N as bound by the process temperature (p...

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Section: Polarizationmentioning

confidence: 99%

Doping of high-Al-content AlGaN grown by MOCVD

Nilsson¹

2014

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“…In order to improve the performances of the LEDs, highly conductive p-type GaN and reliable ohmic contacts are required. However, the as-grown p-type GaN is of high resistance due to the Mg-H complexes [4][5][6]. In order to dissociate the Mg-H complexes, thermal annealing at above 700°C in N 2 ambient is usually employed [7,8].…”

Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of GaN-based light-emitting diodes without pre-activation of p-type GaN

Hu¹,

Wang²,

Zhang³

2016

Nano Online

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We fabricated GaN-based light-emitting diodes (LEDs) without pre-activation of p-type GaN. During the fabrication process, a 100-nm-thick indium tin oxide film was served as the p-type contact layer and annealed at 500°C in N 2 ambient for 20 min to increase its transparency as well as to activate the p-type GaN. The electrical measurements showed that the LEDs were featured by a lower forward voltage and higher wall-plug efficiency in comparison with LEDs using pre-activation of p-type GaN. We discussed the mechanism of activation of p-type GaN at 500°C in N 2 ambient. Furthermore, x-ray photoemission spectroscopy examinations were carried out to study the improved electrical performances of the LEDs without pre-activation of p-type GaN.

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“…Today, p-type Al-rich AlGaN alloys can be obtained; however, the free hole concentration is generally very low [29][30][31][32][33][34][35][36][37][38], mainly limited by the large Mg activation energy (~600 meV) in the end compound AlN [31,39]. In the extreme case, for p-type AlN the reported free hole concentration is only on the order of 10 10 cm −3 [39].…”

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confidence: 99%

Recent Advances on p-Type III-Nitride Nanowires by Molecular Beam Epitaxy

Zhao

2017

Crystals

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p-Type doping represents a key step towards III-nitride (InN, GaN, AlN) optoelectronic devices. In the past, tremendous efforts have been devoted to obtaining high quality p-type III-nitrides, and extraordinary progress has been made in both materials and device aspects. In this article, we intend to discuss a small portion of these processes, focusing on the molecular beam epitaxy (MBE)-grown p-type InN and AlN-two bottleneck material systems that limit the development of III-nitride near-infrared and deep ultraviolet (UV) optoelectronic devices. We will show that by using MBE-grown nanowire structures, the long-lasting p-type doping challenges of InN and AlN can be largely addressed. New aspects of MBE growth of III-nitride nanostructures are also discussed.

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Polarization induced hole doping in graded AlxGa1−xN (x = 0.7 ∼ 1) layer grown by molecular beam epitaxy

Cited by 81 publications

References 18 publications

Doping of high-Al-content AlGaN grown by MOCVD

Doping of high-Al-content AlGaN grown by MOCVD

Fabrication and characterization of GaN-based light-emitting diodes without pre-activation of p-type GaN

Recent Advances on p-Type III-Nitride Nanowires by Molecular Beam Epitaxy

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