Comparison of Ni/Au, Pd/Au, and Cr/Au Metallizations for Ohmic Contacts to p-GaN

Trexler, J.T.; Pearton, S. J.; Holloway, P. H.; Mier, M. G.; Evans, K. R.; Karlicek, R. F.

doi:10.1557/proc-449-1091

Cited by 58 publications

(42 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, the Au exchanged positions with the Niand formed an intimate contact with the GaN layer. These results agree with previous reports in which Ni diffused through the Au capping layer to the surface of the contact where it oxidized [7]. A similar behavior in ESCA depth profiles for the annealed plus cryogenically treated sample is shown in Fig.…”

Section: Electrical Propertiessupporting

confidence: 92%

“…. These characteristics agree with previous studies [7], [8]. The non linear I-V behaviors for Ni/Au contacts continued to improve by heat treatment up to a temperature of 600 °C (Fig.…”

Section: Electrical Propertiessupporting

confidence: 92%

“…For both contacts, the sample that was annealed only and the sample that was cryogenically treated in addition to annealing, there is no evidence of formation of PdO but there is evidence of an Au:Pd solid solution, which is indicated by the Au signal followed by the Pd signal. This new phase (Au:Pd solid solution) was reported by other groups [6], [7]. The Ga and N signals tail out and extend out to the surface, which might indicate the decomposition of the GaN matrix.…”

Section: Electrical Propertiessupporting

confidence: 75%

See 2 more Smart Citations

Microstructure and Electrical Properties of Low Temperature Processed Ohmic Contacts to p-Type GaN

Park¹,

Song²,

Anderson³

2002

ETRI J

View full text Add to dashboard Cite

With Ni/Au and Pd/Au metal schemes and low temperature processing, we formed low resistance stable Ohmic contacts to p‐type GaN. Our investigation was preceded by conventional cleaning, followed by treatment in boiling HNO3:HCl (1:3). Metallization was by thermally evaporating 30 nm Ni/15 nm Au or 25 nm Pd/15 nm Au. After heat treatment in O2 + N2 at various temperatures, the contacts were subsequently cooled in liquid nitrogen. Cryogenic cooling following heat treatment at 600 ·C decreased the specific contact resistance from 9.84·10−4 Ωcm2 to 2.65·10−4 Ωcm2 for the Ni/Au contacts, while this increased it from 1.80·10−4 Ωcm2 to 3.34·10−4 Ωcm2 for the Pd/Au contacts. The Ni/Au contacts showed slightly higher specific contact resistance than the Pd/Au contacts, although they were more stable than the Pd contacts. X‐ray photoelectron spectroscopy depth profiling showed the Ni contacts to be NiO followed by Au at the interface for the Ni/Au contacts, whereas the Pd/Au contacts exhibited a Pd:Au solid solution. The contacts quenched in liquid nitrogen following sintering were much more uniform under atomic force microscopy examination and gave a 3 times lower contact resistance with the Ni/Au design. Current‐voltage‐temperature analysis revealed that conduction was predominantly by thermionic field emission.

show abstract

Section: Electrical Propertiessupporting

confidence: 92%

“…. These characteristics agree with previous studies [7], [8]. The non linear I-V behaviors for Ni/Au contacts continued to improve by heat treatment up to a temperature of 600 °C (Fig.…”

Section: Electrical Propertiessupporting

confidence: 92%

Section: Electrical Propertiessupporting

confidence: 75%

See 1 more Smart Citation

Microstructure and Electrical Properties of Low Temperature Processed Ohmic Contacts to p-Type GaN

Park¹,

Song²,

Anderson³

2002

ETRI J

View full text Add to dashboard Cite

show abstract

“…[4][5][6][7][8][9][10][11] This strategy is based on the Schottky model, which predicts that higher work function metals will result in lower Schottky barriers to p-type semiconductors. The limited experimental evidence available on metal/p-GaN contacts suggests that the Schottky model is at least partially applicable.…”

Section: Introductionmentioning

confidence: 99%

NiIn as an Ohmic Contact to P-GaN

Ingerly

Chang

Chen

1999

MRS Internet j. nitride semicond. res.

View full text Add to dashboard Cite

ABSRTACTBased on the criteria for the solid state exchange reaction with p-GaN, we have investigated the intermetallic compound NiIn as a possible ohmic contact. The contacts were fabricated by depositing NiIn on p-GaN films (p ~ 2 x 10 17 cm -3 ) using RF sputtering from a compound target. The as-deposited, NiIn contacts were found to be rectifying and using I-V characterization a Schottky barrier height of 0.82 eV was measured. Rapid thermal annealing of the contacts was shown to significantly decrease their resistance, with contacts annealed at 800°C for 1 min yielding the lowest resistance. When annealed at 800 °C for 1 min NiIn contacts exhibited a specific contact resistance of 8-9 x 10 -3 Ω cm 2 , as measured by the circular transmission line model. To allow a more universal comparison the more traditional Ni/Au contacts, processed under the same conditions, were used as a standard. Their measured specific contact resistance (ρ c = 1.2 -2.1 x 10 -2 Ω cm 2 ) was significantly higher than that of the NiIn contacts. Demonstrating that NiIn has promise as an ohmic contact to p-GaN and should be studied in greater detail. INTRODUCTIONIt has long been realized that the III-V nitrides have tremendous potential for optoelectronic devices operating in the blue and UV wavelengths as well as for use in high power-high temperature semiconductor devices. The III-V nitrides form a continuous alloy system whose direct band gap ranges from 6.2 eV (AlN) to 3.4 eV (GaN) to 1.9 eV (InN) at room temperature.1 This potentially allows the fabrication of high efficiency optical devices, such as Light Emitting Diodes (LEDs), which can operate from orange to the UV region. The extension into the green and blue wavelengths completes the visible spectrum allowing semiconductor technology to be used for applications such as large full color displays and traffic lights. 2,3Early research into the nitrides outlined several problem areas, which hindered efforts to produce devices based on III-V nitride technology. Particularly the lack of p-GaN made the fabrication of efficient optical devices based on p-n junctions impossible, though some LEDs based on metal-insulator-semiconductors were fabricated. 1,3 Only recently due to advances in ptype doping has GaN started to realize its potential and there are now nitride based devices available. However, the metal contact to p-GaN is an important concern since high contact resistance will substantially reduce the performance of GaN based devices. In fact, the high resistance of the metal/p-GaN contact is one of the most significant issues limiting laser diode performance.Most of the current work on finding low resistance metallizations to p-GaN has focused on high work function elemental metals deposited in multilayer structures. [4][5][6][7][8][9][10][11] This strategy is based on the Schottky model, which predicts that higher work function metals will result in lower Schottky barriers to p-type semiconductors. on metal/p-GaN contacts suggests that the Schottky model is at least partially a...

show abstract

“…Most of the contacts studied for p-GaN are Au-based schemes such as Ni/Au [4 to 6], Pt/Au [7], Cr/Au [4], Pd/Au [8], Ni/Pt/Au [9,10], and Pt/Ni/Au [11]. However, the Au-based contacts generally have poor thermal stability.…”

mentioning

confidence: 99%

Low Resistance and Thermally Stable Pt/Ru Ohmic Contacts to p-Type GaN

Jang

Park

Seong

2000

phys. stat. sol. (a)

View full text Add to dashboard Cite

High-quality Pt (20 nm)/Ru (50 nm) Ohmic contacts to surface-treated p-GaN with lowest resistance and thermal stability are reported. The electrical properties and interfacial reactions of the contacts to GaN were investigated using current±voltage, Auger electron spectroscopy, and glancing angle X-ray diffraction measurements. It is shown that the as-deposited contact produces a specific contact resistance of 7.8(AE2.2) Â 10 ± ±4 Wcm 2 , while the contact annealed at 600 C for 2 min yields a resistance of 2.2(AE2.0) Â 10 ± ±6 Wcm 2 . The latter is believed to be the lowest value reported so far for Ohmic contacts to p-GaN. It is further shown that the contacts exhibit excellent thermal stability during annealing at 600 C.Introduction Due to the rapid progress in the growth and processing of GaN-based semiconductors, the electronic and optoelectronic devices have been successfully fabricated on these semiconductors [1,2]. In order to achieve low power loss and allow high temperature operation of such devices, control of the contact metallurgy with low resistance and thermal stability is of great technological importance.For the contacts to p-GaN, despite the problems such as the difficulty in achieving a carrier concentration !10 18 cm ±3 and the absence of appropriate metals having work functions larger than that of p-GaN (6.5 eV) [3], reasonable electrical properties have been achieved [4 to 11]. Most of the contacts studied for p-GaN are Au-based schemes such as Ni/Au [4 to 6], Pt/Au [7], Cr/Au [4], Pd/Au [8], Ni/Pt/Au [9, 10], and Pt/Ni/Au [11]. However, the Au-based contacts generally have poor thermal stability. Several groups have employed Au-free contact schemes such as W [12], WSi x [12], and Ti/Ta/p-GaN[13] to obtain thermally stable and low resistance Ohmic contacts on p-GaN. However, the W-based contacts produced a rather high contact resistance of %10 ±2 Wcm 2 , indicating that these schemes are not suitable for applications on blue LDs. Furthermore, the Ti/Ta/p-GaN contacts were found to experience atmospheric degradation although the contacts had a low contact resistance of 3 Â 10 ±5 Wcm 2 when annealed at 800 C for 20 min in vacuum ( 4 Â 10 ±4 Pa).Native oxide on p-GaN is detrimental to Ohmic properties. It is, therefore, important to remove native oxide thoroughly for achieving low resistance and thermally stable Ohmic contacts. In a previous work [14], we showed that two-step surface treatment is effective in removing native oxide and increasing a near-surface carrier concentration. In this paper, we report on a new metallization scheme for the formation of low resistance and thermally stable Ohmic contacts to the surface treated-p-GaN.

show abstract

Comparison of Ni/Au, Pd/Au, and Cr/Au Metallizations for Ohmic Contacts to p-GaN

Cited by 58 publications

References 11 publications

Microstructure and Electrical Properties of Low Temperature Processed Ohmic Contacts to p-Type GaN

Microstructure and Electrical Properties of Low Temperature Processed Ohmic Contacts to p-Type GaN

NiIn as an Ohmic Contact to P-GaN

Low Resistance and Thermally Stable Pt/Ru Ohmic Contacts to p-Type GaN

Contact Info

Product

Resources

About