Contact Issues of GaN Technology

Qiao, D.; Yu, L. S.; Lau, S. S.; Sullivan, Gerard; Ruvimov, S.; Liliental‐Weber, Z.

doi:10.1557/s1092578300002234

Cited by 3 publications

(2 citation statements)

References 11 publications

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“…1 Several metallization schemes, including Al/Ti, for ohmic contact on AlGaN/GaN HFETs, bulk GaN and AlGaN layers have been recently reported. [2][3][4][5][6][7][8][9][10][11][12] However, it is difficult to achieve low contact resistance on AlGaN due to that the Schottky barrier height of many metals on AlGaN is larger than 1 eV. 13 For the AlGaN/GaN heterostructure, a two-dimensional electron gas ͑2DEG͒ is induced at the AlGaN/GaN interface due to the piezoelectric effect and spontaneous polarization.…”

Section: Introductionmentioning

confidence: 99%

Ta-based interface ohmic contacts to AlGaN/GaN heterostructures

Qiao

Jia

et al. 2001

Journal of Applied Physics

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Cross-plane electronic and thermal transport properties of p-type La0.67Sr0.33MnO3/LaMnO3 perovskite oxide metal/semiconductor superlattices J. Appl. Phys. 112, 063714 (2012) Polarization Coulomb field scattering in In0.18Al0.82N/AlN/GaN heterostructure field-effect transistors J. Appl. Phys. 112, 054513 (2012) Modulation doping to control the high-density electron gas at a polar/non-polar oxide interface Appl. Phys. Lett. 101, 111604 (2012) Ultra low-resistance palladium silicide Ohmic contacts to lightly doped n-InGaAs Al/Ti based metallization is commonly used for ohmic contacts to n-GaN and related compounds. We have previously reported an ohmic contact scheme specially designed for AlGaN/GaN heterostructure field-effect transistors ͑HFETs͒ ͓D. Qiao et al., Appl. Phys. Lett. 74, 2652 ͑1999͔͒. This scheme, referred to as the ''advancing interface'' contact, takes advantage of the interfacial reactions between the metal layers and the AlGaN barrier layer in the HFET structure. These reactions consume a portion of the barrier, thus facilitating carrier tunneling from the source/drain regions to the channel region. The advancing interface approach has led to consistently low contact resistance on Al 0.25 Ga 0.75 N/GaN HFETs. There are two drawbacks of the Al/Ti based advancing interface scheme, ͑i͒ it requires a capping layer for the ohmic formation annealing since Ti is too reactive and is easily oxidized when annealing is performed in pure N 2 or even in forming gas, and ͑ii͒ the atomic number of Al and that of Ti are too low to yield efficient backscattered electron emission for e-beam lithographic alignment purposes. In this work, we investigated a Ta based advancing interface contact scheme for the HFET structures. We found that the presence of Ta in this ohmic scheme leads to ͑1͒ a specific contact resistivity as low as 5ϫ10 Ϫ7 ⍀ cm 2 , ͑2͒ efficient electron emission for e-beam lithographic alignment, and ͑3͒ elimination of the capping layer for the ohmic annealing.

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Section: Introductionmentioning

confidence: 99%

Ta-based interface ohmic contacts to AlGaN/GaN heterostructures

Qiao

Jia

et al. 2001

Journal of Applied Physics

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“…For example, devices have been reported with f t ¼ 50 GHz, f max ¼ 107 GHz, current sourcing in excess of 1 A/mm, and drain to source breakdown voltages of 250 V [2]. One outstanding problem in the fabrication of the AlGaN/GaN HFET is the difficulty in achieving reliable, reproducible low resistance ohmic contacts [3]. Typical values for contact resistance reported range from 1 W mm to as low as 0.4 W mm, although values as low as 0.15 W mm have been reported [2].…”

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Contact Resistance Reduction in AlGaN/GaN Heterostructure Field Effect Transistors

Amaya

Bardwell

Webb

et al. 2002

phys. stat. sol. (c)

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Two techniques to reduce the contact resistance R C in AlGaN/GaN HFETs have been investigated. Both techniques involve the formation of a matrix of 100 nm diameter pinholes in resist in the contact region using e-beam direct-write lithography. In the first technique, silicon is implanted through the matrix to form doped/damaged filaments extending through the AlGaN cap to the 2DEG. In the second technique, sputtering is used to remove the AlGaN from the pinhole, allowing metal to directly contact the 2DEG. R C was measured as a function of anneal temperature. Si implanted samples gave R C ¼ 0:34 W mm for 800 C annealing, roughly half the value of control samples. Sputter etch samples had R C comparable to that of controls.Introduction AlGaN/GaN Heterostructure Field Effect Transistors (HFET) have shown great potential to provide reasonably high speed combined with very high breakdown voltages and power handling capabilities [1]. For example, devices have been reported with f t ¼ 50 GHz, f max ¼ 107 GHz, current sourcing in excess of 1 A/mm, and drain to source breakdown voltages of 250 V [2]. One outstanding problem in the fabrication of the AlGaN/GaN HFET is the difficulty in achieving reliable, reproducible low resistance ohmic contacts [3]. Typical values for contact resistance reported range from 1 W mm to as low as 0.4 W mm, although values as low as 0.15 W mm have been reported [2]. SPICE simulations using a basic FET model show that a contact resistance of 1 W mm for an HFET could degrade transconductance of the device by as much as 20%.

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