Metal Insulator Semiconductor Tunnel Research Articles

Analysis of characteristics of silicon metal/insulator/semiconductor tunnel diodes with d.c.-plasma-grown oxide

In this work the I–V and C-V characteristics of silicon metal/insulator/semiconductor (MIS) tunnel diodes with d.c.-plasma-grown oxide are analysed in order to investigate further some basic relationships between the oxide properties and the plasma anodization conditions. It is shown that once such relationships are established, the device-grade ultrathin (2–5 nm) oxide can be grown on silicon by use of the plasma anodization technique. The MIS tunnel diodes formed in this way exhibit properties comparable with those containing thermally grown oxide.

Hydrogenated amorphous silicon position sensitive detector

The design, fabrication, and characterization of newly developed hydrogenated amorphous silicon position sensitive detectors (a-Si:H PSDs) which employ a tunnel metal-insulator-semiconductor (MIS) structure fabricated by anodic oxidation processes are described. Tunnel MIS structure is chosen as the a-Si:H PSD structure, since it offers high breakdown voltage compared to a-Si:H pin or Schottky-type structures. PSD process includes two-step anodic oxidation of a-Si:H: (1) oxidation in the dark to passivate defects and shunt paths introduced during the growth of a-Si:H layer and (2) oxidation with light to grow thin native oxide to provide barrier between metal and a-Si:H. The fabricated large-area, two-dimensional PSDs, as large as 3 cm×3 cm, show the incident beam position within error of less than 2% of the length of PSD.

A silicon phototransistor with a MIS tunnel junction emitter

We have fabricated a silicon phototransistor using low-temperature processing. The emitter of the bipolar transistor is an Al-SiO 2 -p-Si tunnel junction. The quantum efficiency gain is 200 at λ = 0.6328 µm. The common-emitter current gain of the analogous three-terminal metal-insulator-semiconductor (MIS) transistor also is 200. This demonstrates the high minority-carrier injection efficiency of the MIS emitter.

A new ’’surface-states’’ mode of switching in M-thin insulator-n-p+ devices

The metal-insulator (tunnel) -n-p device (MISS) is known to display current-controlled negative resistance in its I-V characteristics. This negative resistance behavior originates from a positive feedback interaction between the p-n junction and the tunnel metal insulator semiconductor (MIS) parts of the device. The simple structure of the MISS and its amenability to integration has so far been masked by the incomplete understanding of the physics of operation of the device. In this paper, the effect of the surface states at the semiconductor-insulator interface on the MISS behavior is considered. It is shown that the bias dependence of the charge stored in the surface states reduces the switching voltage Vw below the punch-through or avalanche breakdown limits. A simplified model of the MISS is developed taking into account the different roles of the surface states as charge storage centers, recombination centers, and tunnel-current carrying sites. This model is believed to bridge the gap between the previous theoretical models and experimental works.

MIS-diode as a low-energy X- and γ-ray spectrometer

The paper reviews the metal-insulator-semiconductor (MIS) diode, when the insulator is thinner than 25 Å, and its application to a low energy X- and γ-ray detection is discussed. It is shown that a MIS tunnel minority carrier diode is realized on lightly doped p-type silicon. The application of the diode to low energy X- and γ-ray spectroscopy is demonstrated by an 241Am spectrum with excellent resolution at very low energy and room temperature.

Temperature dependence of current flows in nondegenerate MIS tunnel diodes

Current flows in the nondegenerate metal-insulator-semiconductor (MIS) tunnel diode are temperature sensitive. This temperature sensitivity can be an aid in interpreting the properties of these devices. It allows information regarding the energy distribution of particles tunneling between the metal and the semiconductor to be obtained as well as providing another technique for estimating metal-semiconductor barrier height. Experimental support is given for the existence of minority- and majority-carrier diodes as well as for devices where the current flow is dominated by tunneling between the metal and surface-state levels.

Capacitance properties of MIS tunnel diodes

The theoretical capacitance properties of the metal-insulator-semiconductor (MIS) tunnel diode are described. It is shown that devices with relatively thick insulating layers display properties similar to conventional MIS capacitors, while those with thinner insulating layers differ appreciably. Frequency-dependent features can occur in the characteristics of these devices as a result of a delayed inversion layer response. The presence of such features in experimental devices provides support for the inversion layer clamping process predicted theoretically. Because of these frequency-dependent features, it is shown that caution must be exercised when using MIS tunnel diodes for obtaining surface-state information.

Frequency response of the current multiplication process in MIS tunnel diodes

In contrast to thick insulator structures, metal-insulator-semiconductor (MIS) diodes with very thin insulating regions (<30 Å for the metal-silicon dioxide-silicon system) allow appreciable tunnel current flow between the metal and the semiconductor. Under such conditions, it has recently been shown that multiplication of minority carriers supplied to the contact region can be obtained if the work function of the metal contact is suitably chosen. This paper reports the first quantitative experimental measurements of this multiplication process and its frequency dependence. Gains in the range 100–1000 are reported for AlSiO 2Si devices but the frequency response of the gain mechanism for these devices is found to be relatively restricted, measured values being in the 10 kHz range.

Minority carrier MIS tunnel diodes and their application to electron- and photo-voltaic energy conversion—II. Experiment

The theory of metal-insulator-semiconductor (MIS) tunnel diodes has been described in a companion paper for the case where the insulating layer is so thin that large tunnel currents can flow between the metal and the semiconductor. Of particular interest was the case where the dominant component of tunnel current is between the metal and the minority carrier energy band in the semiconductor (minority carrier diodes). In the present paper, these diodes are investigated experimentally. The differences between minority and majority carrier diodes are demonstrated. Minority carrier diodes are shown to possess properties similar to p- n junction diodes as predicted theoretically. The effectsof different metal contacts, insulator thicknesses, and substrate resistivities are investigated and confirm previous theory. The application of the minority carrier MIS tunnel diodes to energy conversion employing the electron-voltaic effect is investigated experimentally. The diodes were found to be more efficient in this application than p- n junction diodes. Other possible applications of the diodes are as photo-voltaic energy converters, as injecting contacts, and as photo-diodes or elements of photo-diode arrays.

Minority carrier MIS tunnel diodes and their application to electron- and photo-voltaic energy conversion—I. Theory

If the insulating layer in a metal-insulator-semiconductor (MIS) diode is very thin ( <60 A ̊ for AlSiO 2Si), measureable tunnel current can flow between the metal and the semiconductor. If the insulating layer is even thinner ( <30 A ̊ ), tunnel currents are so large that they can significantly disturb the semiconductor from thermal equilibrium. Under such conditions, MIS diodes exhibit properties determined by which of the following tunneling processes is dominant; tunneling between the metal and the majority carrier energy band in the semiconductor, between the metal and the minority carrier energy band, or between the metal abd surface state levels. In the present paper, minority carrier MIS tunnel diodes are analysed using a very general formulation of the tunneling processes through the insulator, transport properties in the semiconductor, and surface state effects. Starting from solutions for diodes with relatively thick insulating layers where the semiconductor is essentially in thermal equilibrium, solutions are obtained for progressively thinner insulating layers until non-equilibrium effects in the semiconductor are observed. It is shown that such minority carrier MIS tunnel diodes with very thin insulating layers possess properties similar to p- n junction diodes including exponential current-voltage characteristics which approach the “ideal diode” law of p- n junction theory. The theory adequately describes the observed properties of experimental devices reported in a companion paper. The diodes have application as injecting contacts, as photodiodes or elements of photodiode arrays, and as energy conversion devices employing the electron- or photo-voltaic effects.

Interaction of Electrons with Impurities and thek≈0Longitudinal Optical Phonon in Metal-Insulator-Semiconductor Tunnel Junctions

Tunneling electrons have been observed to interact with phonons in metal-insulator-semi-conductor (MIS) tunnel junctions including mass-defect phonons, $k\ensuremath{\approx}0$ longitudinal and transverse optical phonons, and zone-boundary phonons. Well-known diffusion techniques have been used to introduce phosphorus into boron-doped silicon producing MIS tunnel junctions having two types of observable mass-defect phonons. These experiments suggest that the mass-defect phonons seen in tunneling arise from an interaction of tunneling electrons with screened, ionized impurity atoms in the reserve region of the semiconductor.

Conductance Extrema in Metal—Insulator—Semiconductor Tunnel Junctions

The conductance in metal—insulator—degenerate semiconductor tunnel junctions is obtained and analyzed. Regions of various shapes of the conductance are determined by use of two reduced parameters. For relatively light degeneracy and high barrier, a conductance minimum occurs at the Fermi energy. Otherwise, a minimum may occur at a voltage equal to or smaller than the Fermi energy and an additional pair of extrema may exist, depending on the type of the semiconductor and the nature of the insulator band edges in providing the tunneling barrier.