Metallization contacts to nonpolar a-plane n-type GaN

Kim, Hyunsoo; Lee, Sung Nam; Park, Yongjo; Kwak, Joon Seop; Seong, Tae Yeon

doi:10.1063/1.2963492

Cited by 48 publications

(23 citation statements)

References 14 publications

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“…Ag is the most commercially used reflector because of its high reflectivity and low contact resistance [11][12][13]. On the one hand, contacts to non-polar and semi-polar GaN produced poorer electrical characteristics than contacts to c-plane (0 0 0 1) samples [14][15][16]. In our previous work [17], we investigated the effect of different polarity on the electrical properties of Ag contacts to semi-polar p-GaN and showed that Ag contacts to (0 0 0 1) c-plane GaN became ohmic after annealing in air, whereas contacts to (1 1 À2 2) semi-polar GaN were non-ohmic.…”

Section: Introductionmentioning

confidence: 99%

Controlling interface oxygen for forming Ag ohmic contact to semi-polar (1 1 −2 2) plane p-type GaN

Park¹,

Han²,

Seong³

2014

Superlattices and Microstructures

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Section: Introductionmentioning

confidence: 99%

Controlling interface oxygen for forming Ag ohmic contact to semi-polar (1 1 −2 2) plane p-type GaN

Park¹,

Han²,

Seong³

2014

Superlattices and Microstructures

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“…These different behaviors could be explained as follows. For Ti/Al contacts to Ga-face n-GaN, annealing at temperatures above 700 C led to the formation of ohmic contacts, being attributed to the formation of AlN, generating N vacancies (donor defects) and two-dimensional electron gases (2DEG) at the AlN/GaN interface 6,12,19 and TiN phase, producing N vacancies. 20 The electrical degradation of Ti/Al contacts to N-face n-GaN at temperatures below 300 C was attributed to the generation of Ga vacancies near the n-GaN surface region caused by Ga outdiffusion.…”

Section: Resultsmentioning

confidence: 99%

Low resistance and thermally stable Ti/Al-based Ohmic contacts to N-face n-GaN for vertical light-emitting diodes by using Ti(Ga) solid solution and TiN layers

Jeon

Yum

Seong

et al. 2012

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The authors report on the formation of highly reliable Ti/Al-based ohmic contacts to N-face n-GaN for high-performance vertical light-emitting diodes by using Ti(Ga) solid solution and TiN layers. The Ti(Ga) solid solution layer is used to minimize the outdiffusion of Ga atoms from the n-GaN surface region. Unlike the Ti/Al contacts, the Ti(Ga)/Ti/Al and Ti(Ga)/TiN/Al samples exhibit ohmic behavior with contact resistivities of 3.9 – 4.8 × 10−4 Ωcm2 after annealing at 250 °C. It was further shown that unlike the Ti(Ga)/TiN/Al samples, the Ti/Al and the Ti(Ga)/Ti/Al samples are largely electrically degraded when annealed at 300 °C in an oven. Based on x-ray photoemission spectroscopy and secondary ion mass spectrometry results, ohmic formation and degradation mechanisms are briefly described and discussed.

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“…For Ti/Al contacts to Ga-face n-GaN, the annealing-induced improvement was attributed to the generation of donorlike N vacancies and 2DEG. 6,11,25 For N-face n-contacts, the annealing-induced degradation was attributed to the absence of polarization-induced 2DEG. 11 These mechanisms are based on the presence of interfacial AlN formed as a result of annealing at temperatures above 400°C.…”

Section: H276mentioning

confidence: 97%

Electrical Properties of Ti/Al Ohmic Contacts to Sulfur-Passivated N-Face n-Type GaN for Vertical-Structure Light-Emitting Diodes

Jung

Seong

Kim

et al. 2009

Electrochem. Solid-State Lett.

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We investigate the electrical properties of Ti/Al ohmic contacts on ͑NH 4 ͒ 2 S x -passivated N-face n-GaN:Si ͑4.2 ϫ 10 18 cm −3 ͒ grown by molecular beam epitaxy. It is shown that the passivation results in an increase in the photoluminescence intensity of n-GaN. Current-voltage ͑I-V͒ measurements show that the passivated samples experience a slight degradation in the electrical properties upon annealing at 300°C, while the untreated samples show some improvement although still nonohmic. Based on the I-V and X-ray photoemission spectroscopy results, we describe the possible mechanisms for the passivation and annealing dependence of the electrical properties of the Ti/Al contacts to the N-face n-GaN.For the realization of solid-state lighting, the fabrication of high performance GaN-based white light-emitting diodes ͑LEDs͒ is crucial. In this connection, vertical-structure LEDs, which can allow high external quantum efficiency, have been widely investigated. 1,2 For example, Wang et al., 2 investigating the electrical properties of vertical GaN-based LEDs fabricated by Ni electroplating and laser lift-off techniques, reported that the n-type side-up vertical LEDs produced much higher output power as compared to conventional top-emission LEDs. Unlike top-emission LEDs, vertical LEDs require the formation of high quality ohmic contacts to both N-face nand p-GaN. 2-5 Ohmic contacts to Ga-face n-GaN can be easily formed using Ti-or V-based schemes. 6-10 It was, however, shown that the formation of ohmic contacts to N-face n-GaN was difficult. [3][4][5] This was attributed to the absence of polarizationinduced two-dimensional electron gas ͑2DEG͒ formed at the AlN/ GaN interface due to the opposite directions of spontaneous polarization built from bulk to surface. 11 However, Jang et al. 5 used a 5 nm thick Pd interlayer to facilitate the formation of interfacial AlN, which played an important role in improving the electrical properties of Ti/Al contacts to N-face n-GaN when annealed at temperatures above 400°C.For Ga-face n-GaN, sulfur passivation was widely performed to produce low resistance n-type ohmic contacts. 9,12,13 For example, Lee et al. 9 reported that nonalloyed Ti/Al contacts to ͑NH 4 ͒ 2 S x -treated n-GaN exhibited ohmic behavior with a contact resistivity of ϳ10 −5 ⍀ cm 2 . Song et al. 14 also showed that nonalloyed Ti/Al contacts yielded a contact resistivity of ϳ10 −4 ⍀ cm 2 when surface-treated by a CH 3 CSNH 2 solution. In this work, we passivated N-face n-GaN using an ͑NH 4 ͒ 2 S x solution to modify the surface property and form low resistance Ti/Al ohmic contacts to N-face n-GaN. It is shown that the sulfur passivation causes an increase in photoluminescence ͑PL͒ intensity of n-GaN. It is also shown that the passivated contacts show better electrical behaviors than untreated samples before and after annealing at 300°C. Molecular beam epitaxy ͑MBE͒ was used to grow a 35 nm thick GaN buffer layer on a sapphire substrate, which was followed by the growth of ͑ϳ1 m thick͒ N-face n-type GaN:Si layers...

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Metallization contacts to nonpolar a-plane n-type GaN

Cited by 48 publications

References 14 publications

Controlling interface oxygen for forming Ag ohmic contact to semi-polar (1 1 −2 2) plane p-type GaN

Controlling interface oxygen for forming Ag ohmic contact to semi-polar (1 1 −2 2) plane p-type GaN

Low resistance and thermally stable Ti/Al-based Ohmic contacts to N-face n-GaN for vertical light-emitting diodes by using Ti(Ga) solid solution and TiN layers

Electrical Properties of Ti/Al Ohmic Contacts to Sulfur-Passivated N-Face n-Type GaN for Vertical-Structure Light-Emitting Diodes

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