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 X 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. V

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/Hz 1 =2 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. Graphene exhibits electronic properties which are relevant for high-frequency applications 1 such as zero-bias detection in passive imaging arrays. 2 Detectors drawing zero bias current offer reduced 1/f-noise compared to biased detectors. Zero-bias detectors are today normally based on heterojunctions or Schottky diodes, reaching noise-equivalent power (NEP) below 20 pW/Hz 1 =2 beyond 100 GHz. 3,4 Zero-bias detection has been demonstrated in graphene field-effect transistors (FETs) with an NEP of 515 pW/Hz 1 =2 at 600 GHz. 5 Self-switching diodes (SSDs) offer a fundamentally different approach to zero-bias detection in which rectification and detection is achieved by a lateral field-effect. 6 Simulations have shown the feasibility of achieving rectification in graphene using SSD structures. 7,8 SSD detectors have previously been realized in other materials 9-12 with the most promising results for GaAs SSDs in which an NEP of 330 pW/Hz 1 =2 at 1.5 THz was observed. 13 In this work, detection with rectifying graphene SSDs at frequencies up to 67 GHz is demonstrated. The SSDs are realized in both as-grown (n-type) and hydrogen-intercalated (p-type) epitaxial graphene on SiC. Figure 1 shows a scanning electron micrograph of a single SSD channel fabricated in epitaxial graphene. The narrow graphene channel behaves as a lateral nanowire transistor. 6 The surrounding flanges act as lateral gates which are directly connected to the drain such that the drain voltage is simultaneously applied to the gates. This has the effect of modulating the carrier density in the nanowire channel generating a nonlinear current-voltage characteristic. 14 The inset shows an SSD design implemented for RF detection with nine nanowire channels acting in parallel to reduce resistance and NEP. 15 The SSDs were fabricated at the end of a 70 lm coplanar transmission line, in order to provide a partial RF match.Graphene was grown on the Si-face of two 20 Â 20 mm 2 nominally on-axis semi-insulating (SI) 4H-SiC substrates in a horizontal hot wall chemical vapor deposition (CVD) reactor. 16 Graphene growth was carried out at 1300 C to 1400 C in vacuum after an initial in-situ surface preparation of the substrates in a hydrogen/silane background. One of the samples was then intercalated in hydrogen at a temperature (pressure) of 800 C (500 mbar) in order to obtain quasi-free standing graphene. SSDs and supplementary test structures were fabricated on the graphene layers with and without H-intercalation. As-grown samples then consisted of a monolayer plus carbon buf...

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International audienceLowering 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 δ-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 × 1012 cm−2 to 1.5 × 1012 cm−2 (−44%), the noise equivalent power (NEP) improved from 130 pW/Hz½ to 87 pW/Hz½ (−33%)

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