The vertical metal insulator semiconductor tunnel transistor: A proposed Fowler-Nordheim tunneling device

We propose a new field-effect transistor, the vertical metal insulator semiconductor tunnel transistor (VMISTT) which operates using gate modulation of the Fowler-Nordheim tunneling current through a metal insulator semiconductor (M-I-S) diode. The VMISTT has significant advantages over the metal-oxide-semiconductor field-effect transistor in device scaling. In order to allow room-temperature operation of the VMISTT, the tunnel oxide has to be optimized for the metal-to-insulator barrier height and the current-voltage characteristics. We have grown TiO2 layers as the tunnel insulator by oxidizing 7 and 10 nm thick Ti metal films vacuum-evaporated on silicon substrates, and characterized the films by current-voltage and capacitance-voltage techniques. The quality of the oxide films showed variations, depending on the oxidation temperatures in the range of 450-550 degrees C. Fowler-Nordheim tunneling was observed at low temperatures at bias voltage of 2 V and above and a barrier height of approximately 0.4 eV was calculated. Leakage currents present were due Schottky-barrier emission at room-temperature, and hopping at liquid nitrogen temperature

The theory of operation of transistorized Marx bank circuits.

A theory of operation of transistorized Marx bank circuits has been formulated. It has been shown quantitatively that the current-mode second breakdown of transistors is the basic phenomenon involved. The analysis reveals that physical parameters, like the length of and the doping density in the epitaxial collector, the forward dc amplification factor, and the avalanche multiplication gain of the transistors, play important roles in the mechanism. The theory has been applied to explain a number of experimentally observed characteristics of the circuit

Nonuniform doping of the collector in avalanche transistors to improve the performance of Marx bank circuits.

It is shown that the avalanche multiplication factor of transistors, which plays a key role in the functioning of the Marx bank circuit, can be considerably enhanced when the collector has a Gaussian doping profile, compared to uniform doping. The limiting of the maximum field in the collector, and the base push out are the events involved in the occurrence of the current mode second breakdown of avalanche transistors in the Marx circuit. Calculations show that the limiting of the maximum field, followed by the base push out, is the sequence conducive to the enhancement of the avalanche gain. Preliminary experimental assessment of the doping profiles of the same model of transistors from two different manufacturers supports the proposed idea

The principle of operation of the avalanche transistor-based Marx bank circuit: A new perspective.

The principle of operation of the transistor-based Marx bank circuit has been examined. It was experimentally observed that stage-wise increase of reverse voltage does not occur. This cannot be explained by the principle of operation understood so far. A new explanation, consistent with the experimental observations and associating current-mode second breakdown of transistors, is proposed. A few experimental observations made by earlier workers have also been justified in light of the new current-controlled mechanism

Schottky diode back contacts for high frequency capacitance studies on semiconductors

A technique using large area Schottky diode back contacts has been developed to enable high frequency capacitance studies to be carried out on semiconductors without the need to fabricate high quality ohmic back contacts. This technique will find application for very high resistivity materials or for the characterization of novel semiconductors when a method of producing good ohmic contacts has not been established. In this method a back contact much larger in area than the front contact diode under test is used. It is then found that accurate capacitance-voltage measurements can be made of the ionized doping density and, provided the back contact has sufficient leakage, the built-in potential can also be measured. Such specimens may also be used for characterization using the deep level transient spectroscopy (DLTS) technique and this is demonstrated by obtaining DLTS spectra from very high resistivity silicon specimens containing oxygen precipitates and comparing these to similar spectra obtained from more highly doped material

The Oxford Democrat : Vol. 36, No. 36 - September 24, 1869

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Observation of Fowler-Nordheim tunneling for room temperature operation of the vertical metal-oxide tunnel transistor

We propose a new field effect transistor, the vertical metal-oxide tunnel transistor (VMOTT) which operates using gate modulation of the Fowler-Nordheim tunneling current through the channel oxide. The VMOTT has significant advantages over the metal-oxide-semiconductor field effect transistor (MOSFET) in device scaling. In order to allow room-temperature operation of the VMOTT, the tunnel oxide has to be optimized for the metal-to-oxide barrier height and the current-voltage characteristics. We have grown TiO2 layers as the tunnel oxide by oxidising 5-10 nm thick Ti metal films vacuum-evaporated on silicon substrates, and characterized the films by current-voltage and capacitance-voltage techniques. The quality of the oxide films showed variations, depending on the oxidation temperatures in the range of 300-500 C. Some of the samples were subjected to a post-oxidation anneal in nitrogen ambient at 700 C. Fowler-Nordheim tunneling was observed clearly at room temperature, which was further confirmed at low temperatures in the samples oxidised at 500 C and annealed subsequently

Semi-insulating silicon by deep level doping for radio frequency applications

Deep level Mn doping by ion implantation and RTA have been used for the first time to make very high resistivity Czochralski silicon substrates up to 10 kΩcm and on the average, resistivity increased nearly ten-fold. Interesting features, like trapping by end-of-range defects, out-diffusion and partial activation of Mn dopant atoms were observed