| 1. |
- Westlund, Andreas, 1985, et al.
(author)
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Graphene self-switching diodes as zero-bias microwave detectors
- 2015
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 106:9, s. 093116-
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Journal article (peer-reviewed)abstract
- Self-switching diodes (SSDs) were fabricated on as-grown and hydrogen-intercalated epitaxial graphene on SiC. The SSDs were characterized as zero-bias detectors with on-wafer measurements from 1 to 67 GHz. The lowest noise-equivalent power (NEP) was observed in SSDs on the hydrogen-intercalated sample, where a flat NEP of 2.2 nW/Hz½ and responsivity of 3.9 V/W were measured across the band. The measured NEP demonstrates the potential of graphene SSDs as zero-bias microwave detectors.
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| 2. |
- Westlund, Andreas, 1985, et al.
(author)
-
Nanochannel diodes based on InAs/Al80Ga20Sb heterostructures: Fabrication and zero-bias detector properties
- 2015
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In: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics. - : American Vacuum Society. - 2166-2746 .- 2166-2754. ; 33:2, s. 021207-
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Journal article (peer-reviewed)abstract
- The authors present a novel process for fabrication of deep submicron isolation patterns in InAs/Al80Ga20Sb heterostructures. The process is demonstrated by processing InAs/Al80Ga20Sb self-switching diodes (SSDs). SSDs require high-resolution isolation patterns, which presents a major fabrication challenge because of the oxidation sensitivity of Al(Ga)Sb alloys. The presented fabrication process completely avoided exposure of Al(Ga)Sb to air and resulted in an isolation pattern with a feature size down to 35 nm. The process was based on a dry etch of isolating trenches, in situ removal of the resist etch mask followed by in situ encapsulation of etched surfaces by silicon nitride. The applicability of the InAs/Al80Ga20Sb SSD process was demonstrated with on-wafer RF measurements of zero-bias detection up to 315 GHz. Below 50 GHz, the detector's noise equivalent power was estimated to less than 100 pW/Hz½ .
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| 3. |
- Westlund, Andreas, 1985, et al.
(author)
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On the effect of delta-doping in self-switching diodes
- 2014
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:9, s. Article Number: 093505 -
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Journal article (peer-reviewed)abstract
- Lowering the carrier concentration is presented as a way to considerably improve the performance of self-switching diode (SSD) detectors. A physics-based theoretical model was used to derive an expression for the responsivity of SSDs as a function of carrier concentration, mobility, and design parameters. Monte Carlo simulations confirmed the modeled effect of varying carrier concentration and channel width. SSDs were fabricated in InAs heterostructures with different delta-doping levels. Radio frequency (RF) characterization at 50 GHz reproduced the modeled trends. By reducing the carrier concentration in InAs SSDs with 40 nm wide channels from 2.7 x 10(12) cm(-2) to 1.5 x 10(12) cm(-2) (-44%), the noise equivalent power (NEP) improved from 130 pW/Hz(1/2) to 87 pW/Hz(1/2) (-33%).
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| 4. |
- Westlund, Andreas, 1985, et al.
(author)
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Optimization and small-signal modeling of zero-bias InAs self-switching diode detectors
- 2015
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In: Solid-State Electronics. - : Elsevier BV. - 0038-1101. ; 104:Feb, s. 79-85
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Journal article (peer-reviewed)abstract
- Design optimization of the InAs self-switching diode (SSD) intended for direct zero-bias THz detection is presented. The SSD, which consists of nanometer-sized channels in parallel, was described using an equivalent small-signal circuit. Expressions for voltage responsivity and noise equivalent power (NEP) were derived in terms of geometrical design parameters of the SSD, i.e. the channel length and the number of channels. Modeled design dependencies were confirmed by RF and DC measurements on InAs SSDs. In terms of NEP, an optimum number of channels were found with the detector driven by a 50 Omega source. With a matched source, the model predicted a responsivity of 1900 V/W and NEP of 7.7 pW/Hz(1/2) for a single-channel InAs SSD with 35 nm channel width. Monte Carlo device simulations supported observed design dependencies. The proposed small-signal model can be used to optimize SSDs of any material system for low-noise and high-frequency operation as zero-bias detectors. In large signal measurements, the responsivity of the InAs SSDs exhibited a 1 dB deviation from linear responsivity at an input power of -3 dBm from a 50 Omega source.
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| 5. |
- Westlund, Andreas, 1985, et al.
(author)
-
Terahertz detection in zero-bias InAs self-switching diodes at room temperature
- 2013
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:13
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Journal article (peer-reviewed)abstract
- RF characterization of InAs self-switching diodes (SSDs) is reported. On-wafer measurements revealed no roll-off in responsivity in the range of 2-315 GHz. At 50 GHz, a responsivity of 17 V/W and a noise-equivalent power (NEP) of 150 pW/Hz(1/2) was observed for the SSD when driven by a 50 Omega source. With a conjugately matched source, a responsivity of 34 V/W and an NEP of 65 pW/Hz(1/2) were estimated. An antenna-coupled SSD demonstrated a responsivity of 0.7 V/W at 600 GHz. The results demonstrate the feasibility of zero-bias terahertz detection with high-electron mobility InAs SSDs up to and beyond 100 GHz.
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