Self-powered single semiconductor nanowire photodetector

Abstract

Self-powered photodetectors have been fabricated from a single germanium nanowire (NW) in the metal-semiconductor-metal (MSM) device configuration. The self-powered devices show a high photoresponse (responsivity ∼ 10-10 A W) in the wavelength range 300-1100 nm. It has been established from I-V characteristics that asymmetry exists in the Schottky barrier height (SBH) at the two MS contacts. We have used simulation to establish that the asymmetric SBH at the metal contacts in an MSM device is a major cause for the 'built-in' axial field that leads to separation of a light generated electron-hole pair in the absence of an applied bias. Thus, even in the absence of external bias, the photogenerated carriers can be separated, which then diffuse to the appropriate electrodes driven by the 'built-in' axial field. We also point out the physical origins that can lead to unequal barrier heights in seemingly identical NW/metal junctions in a MSM device.

Highly Responsive, Polarization Sensitive, Self-Biased Single GeO2-Ge Nanowire Device for Broadband and Low Power Photodetectors

“…This gives rise to an appreciable photocurrent even without application of any bias (zero bias), as shown in Figure b,c. Zero-bias photocurrent has also been reported previously in Ge nanowire …”

Broadband (Ultraviolet to Near-Infrared) Photodetector Fabricated in n-ZnO/p-Si Nanowires Core–Shell Arrays with Ligand-Free Plasmonic Au Nanoparticles

“…12,13 These single NW detectors can function as self-biased (zero applied bias) detectors with high responsivity of the order of 10 4 A/W with Si NW 12 and 10 5 A/W with Ge NW. 14 Inspite of ultrahigh responsivity over a broad spectral range and extremely low power dissipation, these detectors suffer from the disadvantage that the fabrication process is lithography intensive and needs availability of nano-lithography facilities.…”

“…An example of utilizing the surface oxide and band bending as an active agent of inhibiting carrier recombination has been done for a single Ge NW-based broadband (300–1100 nm) photodetector, where a peak responsivity of 10 7 A/W at low power consumption has been achieved. , Broadband high responsivity in single Si NW- and Si NW array-based detectors has been achieved using similar concepts. , These single NW detectors can function as self-biased (zero applied bias) detectors with high responsivity of the order of 10 4 A/W with Si NW and 10 5 A/W with Ge NW . Despite ultrahigh responsivity over a broad spectral range and extremely low power dissipation, these detectors suffer from the disadvantage that the fabrication process is lithography-intensive and needs the availability of nanolithography facilities.…”

Bias-Switchable Photoconductance in a Nanoscale Ge Photodetector Operated in the Negative Differential Resistance Regime

“…Group IV based photonic components are a very active area of research with extensive interest in CMOS compatible photodetectors. In this respect, Ge is considered a key material in the visible and near-infrared region, covering the C-band optical communication range. , In terms of detector geometry, bottom-up, vapor–liquid–solid (VLS) grown Ge nanowires (NWs) , have gained particular attention. − Aside from physical advantages in their optoelectronic structure, NWs are also of foremost interest due to their technologically relevant scaling capability and compatibility with CMOS platforms. − Most notably, applied for photodetectors, NWs can be viewed as nanocylinder resonators. Such resonators are capable of trapping light in circulating orbits by multiple total internal reflections from the periphery .…”

“…In contrast to common metal–germanide formation, the Al–Ge exchange overcomes the difficulty in reproducibly and deterministically defining the stoichiometric phase as the stability of conventional NiGe–Ge nanojunctions is a key variability issue. , Recently, the unconventional photoexcitation phenomenon of negative photoconductance (NPC), where the generated photocurrent being lower than the dark current, was reported in highly n-doped Ge NWs and was linked to charge carrier trapping . Moreover, in the quest to minimize dark currents, thus enhancing the performance of Ge photodetectors, concepts employing asymmetric contacts, self-powered operation, or operating the detector at the quantum ballistic limit were demonstrated. In this work, we follow a disctintive approach, where for the first time the transferred-electron effect in Ge is exploited, to enable negative differential resistance (NDR) driven dark current suppression.…”