Formation mechanism of Ohmic contacts on AlGaN∕GaN heterostructure: Electrical and microstructural characterizations

Wang, Liang; Mohammed, Fitih M.; Adesida, I.

doi:10.1063/1.2903482

Cited by 77 publications

(48 citation statements)

References 32 publications

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“…In contrast, the inclusions are not observed in the TEM of the as-deposited sample, because the as-deposited sample shows the significantly rectifying property, and we think that the Ohmic contact is not present if the inclusions are not generated, and the contact potential of inclusions is much lower than others. Figure 4b shows that the severe interfacial reaction was not observed beyond the inclusions, which means that the extraordinary Ohmic contact for our samples could be generated by the inclusions, since these inclusions are stuck in the contact layer and cause the distortion of the contact potential barrier, i.e., the spike contact [22][23][24][25], which is able to lead to the more efficient conduction paths between electrode pad and the MS contact layers than the rest intact region beyond the inclusions.…”

Section: Resultsmentioning

confidence: 82%

Temperature dependence of Ohmic contacts of In0.83Ga0.17As photodiodes and its correlation with interface microstructure

et al. 2015

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The temperature-dependent electrical properties of Au Ohmic contacts of In 0.83 Ga 0.17 As photodiodes were systematically investigated in the temperature range 163-373 K. For two annealed sample, the novel temperature behavior of the specific contact resistivity q sc was observed and exhibits similarity to that of 'metal,' describable by a T 2.01 and T 2.19 dependence. The microscopic interfacial analysis from transmission electron microscope (TEM) indicated that the Au protrusions penetrating into the contact layer, with a density of 9 9 10 7 and 2.0 9 10 8 cm -2 , respectively, could cause this phenomenon by acting as the more efficient conduction channels. By fabricating the extended wavelength In 0.83-Ga 0.17 As photodiode and deducing the series resistance from the current-voltage-temperature (I-V-T) characteristics, it is proved that the series resistance is mainly caused by the contact resistance of the metal-semiconductor (MS) interface. The results are very meaningful for the application of the extended wavelength In 0.83 Ga 0.17 As photodiode.

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Section: Resultsmentioning

confidence: 82%

Temperature dependence of Ohmic contacts of In0.83Ga0.17As photodiodes and its correlation with interface microstructure

et al. 2015

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“…It is believed that Ti reacts with GaN and forms TiN at elevated temperatures, extracting N from GaN and generating N-vacancies in the GaN layer. N-vacancies act in turn as an effective n-type dopant, which enables the tunneling contact mechanism [5], [6]. …”

Section: Resultsmentioning

confidence: 99%

GaN Ohmic contact resistance vs temperature

Fontserè

Pérez‐Tomás

Placidi

et al. 2011

Proceedings of the 8th Spanish Conference on Electron Devices, CDE'2011

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+34 93 594 77 00 AbstractThe temperature impact on the Ohmic contact to Gallium Nitride (GaN) device properties is investigated in the range of 25ºC to 300ºC by means of the Transmission Line Method (TLM) technique. This study is centered in two kinds of Ohmic contacts: Implanted N + GaN and heterojunction AlGaN/GaN contacts. For N + contact resistance behavior is explained in terms of the field-effect or thermionic field effect current transport mechanism. However, the heterojunction contact resistance behavior is explained by the mobility properties in the two dimensional electron gas. IntroductionWhenever a metal-semiconductor (M-S) are in intimate contact, there exists a potential barrier (i.e., Schottky Barrier) between the two that prevents most charge carriers (electrons or holes) from passing from one to the other. Methods are deployed in order to manipulate the band structure so that the tunneling transport mechanism can dominate. The most common process to obtain an Ohmic M-S contact is highly doping the semiconductor region (N + for n-type). When the semiconductor has been highly doped, the depletion barrier becomes as thin as ~3 nm, enabling the electrons going through the barrier by the aforementioned tunneling transport. Gallium Nitride (GaN) based devices are not an exception to this rule. The scenario for contact to a polar heterojunction (HJ) AlGaN/GaN (where a two dimensional -2DEG-has been formed) may be regarded as analogous to the N + contact. Here, the thinning of the barrier is achieved by recessing the AlGaN barrier, again doping and/or selecting the metal stack that will react after high temperature anneal. The understanding of the Ohmic M-S contact is of great importance to obtain an optimal GaN based solid-state electrical device. The Contact resistance properties are investigated using the well known Transmission Line Method (TLM) technique to determine both sheet resistance (R sh ) of the semiconductor between the strips, the contact resistance (U c ) and the specific contact resistivity (R c ) of metal Ohmic contacts to semiconductor [1]. This technique is based in the extraction of the resistance between two metal strips at a varying distance. In this paper, the contact properties are analyzed in the temperature range of 25 o C to 300 o C for both, an Implanted N + GaN and HJ AlGaN/GaN contacts. Experimental DetailsTwo types of contacts have been investigated. Implanted N + GaN contacts, as shown in a Fig.1(a), present a p-type GaN epilayer (6 Pm tick), as starting material, grown on a c-plane sapphire substrate. A Si + implantation at 160 keV and with a dose of 3×10 15 cm -2 was performed, resulting in a ~ 0.2 Pm deep region. Various annealing was realized both with and without protection in an N 2 ambient to activate the implanted Si. Finally, Ti and Al with 35 nm and 155 nm thicknesses were sequentially deposited by sputtering and patterned by lift-off process, to obtain the TLM structures. Fig.1(b) presents an HJ AlGaN/GaN contact TLM structures were fabricated on a previously o...

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“…The overlying Ti, or Ni, or Pt layer serves as a barrier to prevent interdiffusion with the top Au, which has the role of reducing the sheet resistance. A detailed structural investigation of Ti/Al/Mo/Au ohmic contacts on AlGaN/GaN structures as a function of annealing temperature can be found in [26].…”

Section: Temperature-activated Degradation Mechanismsmentioning

confidence: 99%

Reliability of GaN-Based HEMT devices

Menozzi

2008

2008 Conference on Optoelectronic and Microelectronic Materials and Devices

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This paper reviews the main problems characterizing the past and present of GaN-based HEMT reliability. Some general considerations on the maturity of this technology and published lifetesting extrapolations are followed by a review of physical degradation mechanisms, subdivided between temperature-activated and electrical ones, the latter generally linked with the much-debated "current collapse". The paper ends with some conclusive remarks on what has been achieved and what still lies ahead.

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Formation mechanism of Ohmic contacts on AlGaN∕GaN heterostructure: Electrical and microstructural characterizations

Cited by 77 publications

References 32 publications

Temperature dependence of Ohmic contacts of In0.83Ga0.17As photodiodes and its correlation with interface microstructure

Temperature dependence of Ohmic contacts of In0.83Ga0.17As photodiodes and its correlation with interface microstructure

GaN Ohmic contact resistance vs temperature

Reliability of GaN-Based HEMT devices

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