Ion-implanted
 n
 +
 contacts for K
 a
 band GaAs Gunn-effect diodes

Lee, D.H.; Berenz, J.; Bernick, R.L.

doi:10.1049/el:19750145

Cited by 6 publications

(6 citation statements)

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“…In addition, most authors have reported very low electrical activity for anneal temperatures below 700~ However, dissociation of the GaAs surface can begin as low as 600~ unless special precautions are taken to either control the atmosphere or encapsulate the surface. Our initial attempts using dielectric encapsulation resulted in some attractive profiles and excellent device results (6,7). However, controlled profiles were difficult to reproduce regularly due to the poor quality of the dielectric encapsulants.…”

Section: Resultsmentioning

confidence: 99%

“…We have utilized ion implantation to fabricate high-low READ GaAs IMPATT diodes (6) and state-of-the-art Ka-band GaAs Gunn effect diodes (7). However, the results reported to date indicate that, in general, the doping efficiencies of the n-type implanted species are low unless long annealing periods are used.…”

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confidence: 99%

“…Implantation is considered to be an attractive alternative to diffusion for the creation of thin heavily doped n-type regions in GaAs (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). We have utilized ion implantation to fabricate high-low READ GaAs IMPATT diodes (6) and state-of-the-art Ka-band GaAs Gunn effect diodes (7).…”

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confidence: 99%

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Annealing of Ion‐Implanted GaAs in a Controlled Atmosphere

Malbon

Lee

Whelan

1976

J. Electrochem. Soc.

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Implantation is considered to be an attractive alternative to diffusion for the creation of thin heavily doped n-type regions in GaAs (1-15). We have utilized ion implantation to fabricate high-low READ GaAs IMPATT diodes (6) and state-of-the-art Ka-band GaAs Gunn effect diodes (7). However, the results reported to date indicate that, in general, the doping efficiencies of the n-type implanted species are low unless long annealing periods are used. Lengthy annealing times are unattractive because diffusion tends to excessively broaden the impurity doping gradients and thus impair device performance. Even for short anneal times within the range of commonly used annealing temperatures, 700~176it is necessary to take special precautions to minimize erosion of the GaAs surfaces. A variety of approaches have been used. These include sealing the GaAs both with and without a dielectric encapsulant in evacuated quartz ampuls prior to annealing (4, 8). The encapsulants have included SiO2 (3, 4, 6, 9), Si3N4 (8, 9), A12Oa (11, 12), and 14). However various problems associated with uncontrolled contamination and interdiffusion at the encapsulant-GaAs interface have been noted (15).This paper describes the results of substituting a controlled atmosphere for the dielectric encapsulant to protect the GaAs surface during high temperature anneals. Epitaxial materials technology has demonstrated that polished substrates can be maintained at elevated temperature with minimal surface degradation in a flowing high purity hydrogen atmosphere. Taking advantage of this experience, an anneal system was designed which utilizes a controlled atmosphere of high purity hydrogen (He) in conjunction with an arsenic (As) source to protect the GaAs surface during annealing. The system was used to anneal epitaxial GaAs films implanted with either silicon ions or sulfur ions to create thin, highly doped n-type layers. The epitaxial surfaces exhibited no degradation after anneals at 800~ for 20 min. The electrical results indicate that the apparent electrical conversion efficiencies achieved for the implanted layers were as high as 85% for the 800~ 20 min anneal. ExperimentalThe GaAs epitaxial material used in this investigation was grown by the He-Ga-AsCts vapor phase technique on heavily Te-doped n+-substrates oriented 3 ~ Off the <100> toward the <111>. The epitaxial layers were doped with sulfur and were electrically uniform in depth with net donor concentrations within the range 2-8 X 1015 cm -~. The epitaxial layers were implanted at room temperature with either 120 keV silicon ions or 140 keV sulfur ions. In the case of the silicon implants it was concluded after careful analysis of the separated ion spectrum that the implanted species was 28Si+ with less than 1% of other possible molecular components (e.g., N2+). To minimize channeling effects, the GaAs lattice was oriented to appear random to the incident ion beam. Under this condition, a first order approximation to the implanted ion distribution is Gaussian with a mean projected range Rp...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Annealing of Ion‐Implanted GaAs in a Controlled Atmosphere

Malbon

Lee

Whelan

1976

J. Electrochem. Soc.

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“…This work demonstrates that a shallow sulfur diffusion [as well as ion implantation (10)] should be successful in lowering the contact resistance of GaAs TED's from being the major part of the total device resistance, to a value that is 1-10% of the total device resistance. This is crucial for uniform device p a r a m eters and reduced power dissipation in integrated circuit applications of TED's.…”

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confidence: 94%

Ohmic Contacts to GaAs Transferred Electron Devices

Johnson

Huang

1978

J. Electrochem. Soc.

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The specific contact resistance of A u / G e / N i alloy contacts to G a A s for transferred electron devices has been measured. It is found that a shallow sulfur diffusion under the contact is effective in reducing the specific contact resistance by up to two orders of magnitude. This procedure is expected to improve the uniformity of threshold and bias voltages in integrated circuit configurations by making the contact resistance only 1-10% of the total device resistance.Because of the low doping found in GaAs transferred electron devices (TED's) for microwave applications, the contact resistance to the device is the major part of the total device resistance. A survey of the literature indicates that for a given doping level, the contact resistance can vary uP to two orders of magnitude as the processing parameters are varied (1-5). Significant variation can also occur across a wafer in a given run. This situation is allowable for discrete device configurations where postsorting is possible. In integrated circuit configurations, however, local variations are intolerable because threshold and bias voltages must be uniform from one device to the next in the same circuit. The purpose of this paper is to show that a shallow sulfur diffusion u n d e r the metallization pads can reduce the contact resistance to 1-10% of the total device resistance. The specific contact resistance is lowered by approximately two orders of magnitude over that measured on nondiffused samples.The metallurgical and electrical properties of alloyed A u -G e / N i films on n -t y p e GaAs are relatively well understood (1). Edwards, Hartman, and Torrens (2) have summarized specific contact resistance data of this and other contact alloys to GaAs through mid-1971. In general, their data show two order of magnitude variation in the specific contact resistance which ranges from a m e a n of 3 • 10 -3 ~-c m at a doping level of mid-1015/cm 8 to 10 -4 ~-c m at 1017/cm ~. Robinson (3) and Yu (4) have independently confirmed that by process optimization, the mean specific contact resistance can be lowered by up to one order of magnitude. For GaAs TED's doped from mid-1015/cm ~ to mid-1016/cm 3, the specific contact resistance values reported as well as those measured in our laboratories give a device contact resistance far greater than the intrinsic device resistance (typically 3000~). To lower the contact resistance to 1-10% of the total device resistance, a specific contact resistance of ~10 -5 ~-c m is required. The exact value depends on the specific device configuration. This value is two orders of magnitude lower than that reported, and hence can only be achieved by the formation of a shallow n-t-layer below the contact to give a doping level of mid-1017/cm 3 to mid-101S/cm ~.The samples used in this experiment were semiinsulating GaAs substrates on which 25 #m vapor phase epitaxy layers were grown. The typical doping range was mid-1015/cm 8 to mid-1016/cm 3 n -t y p e (Si). Ohmic contacts were formed by evaporation of a gold/ 12 weight perc...

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“…The recent advent of ion implantation technology in GaAs has generated much enthusiasm for the fabrication of optoelectronic and microwave devices as demonstrated by injection lasers (1), FET's (2,3), TED's (4), and IMPATT diodes (5). Inasmuch as the fabrication of these devices requires a high degree of sopb/stication, the production of shallow layers having precisely controlled doping concentrations and a welldefined dopant profile is an important goal of ion implantation efforts.…”

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confidence: 99%