Superfast fronts of impact ionization in initially unbiased layered semiconductor structures

Abstract

Rodin, P.; Ebert, U.M.; Hundsdorfer, W.; Grekhov, I.V. Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. A mode of impact ionization breakdown of a p -n junction is suggested: We demonstrate that when a sufficiently sharp voltage ramp is applied in reverse direction to an initially unbiased equilibrium p ϩ -n -n ϩ structure, after some delay the system will reach a high conductivity state via the propagation of a superfast impact ionization front. The front travels towards the anode with a velocity v f several times larger than the saturated drift velocity of electrons v s leaving a dense electron-hole plasma behind. The excitation of the superfast front corresponds to the transition from the common avalanche breakdown of a semiconductor structure to a collective mode of streamer-like breakdown. We propose that similar fronts can be excited not in layered structures but in plain bulk samples without p -n junctions. Our numerical simulations apply to a Si structure with typical thickness of Wϳ100 m switched in series with a load Rϳ100 ⍀, with a voltage ramp of AϾ10 12 V/s applied to the whole system. Our simulations show that first there is a delay of about 1 ns during which the voltage reaches a value of several kilovolts. Then, as the front is triggered, the voltage abruptly breaks down to several hundreds of volts within ϳ100 ps. This provides a voltage ramp of up to ϳ2ϫ10 13 V/s hence up to 10 times sharper than the externally applied ramp. We unravel the source of initial carriers which trigger the front, explain the orig...

Laplacian Instability of Planar Streamer Ionization Fronts—An Example of Pulled Front Analysis

“…The electric field E = −∇φ then is determined by the solution of the Poisson equation −∇ 2 φ = ρ and by the boundary conditions on φ. In certain ionization fronts in semiconductor devices [43], it is essential that the equivalent of ρ does not vanish in the non-ionized region. In the gas discharges considered here, on the other hand, it is reasonable to assume that the non-ionized initial state with σ ≡ 0 also has a vanishing ion density ρ ≡ 0, and therefore no space charges.…”

Positive streamers in air and nitrogen of varying density: experiments on similarity laws

“…We also recall experimental work on streamers in fluid nitrogen and argon [16]. Streamer-like phenomena also occur in fast semiconductor switches [17]. While in all these cases, the density of neutral particles is of the order of or considerably larger than in air at standard temperature and pressure, much lower densities are of interest in geophysics.…”

Impact Ionization MOS (I-MOS)—Part I: Device and Circuit Simulations

“…1) Statistical retardation delay: This is the delay in generating the seed carrier used to initiate the avalanche process and has been quantified previously to be negligible in the I-MOS [24], [25], [29], and 2) Avalanche build-up time: For devices that operate in the post-breakdown mode, the avalanche build-up delay required to get to the steady state is usually small and is of the same order of magnitude as the transit time of the device [26]. These modes of avalanche initiation and build-up have been observed in other high speed impact-ionization based devices including IMPATT and TRAPATT oscillators that operate at more than 200 GHz [27].…”