Thermionic emission

About: Thermionic emission is a research topic. Over the lifetime, 6099 publications have been published within this topic receiving 97892 citations. The topic is also known as: Edison effect.

The Richardson constant for thermionic emission in Schottky barrier diodes

Abstract: The Richardson equation appropriate to thermionic emission in Schottky barrier diodes is derived. For a semiconductor having an energy band with ellipsoidal constant-energy surfaces in momentum space, the Richardson constant A 1 ∗ associated with a single energy minimum is A ∗ 1 =4φ qk 2 h 3 (l 2 m y m z +m 2 m z m x +n 2 m x m y ) 1 2 where l, m and n are the direction cosines of the normal to the emitting plane relative to the principal axes of the ellipsoid and mx, my and mz are the components of the effective mass tensor. In the Ge conduction band, summation of emission from all the energy minima gives maximum and minimum ratios of A∗ to the free electron value A (= 120 A/cm2/°K2) of 1·19 and 1·07 for the 〈100〉 and 〈111〉 directions respectively. In the silicon conduction band, maximum and minimum ratios of 2·15 and 2·05 occur for the 〈111〉 and 〈100〉 directions respectively. The theoretical predictions are in good agreement with experimental results from W-Si and Au-GaAs diodes.

A review of the theory and technology for ohmic contacts to group III–V compound semiconductors

Abstract: The technology for ohmic contacts to group III–V compound semiconductors is reviewed in this paper. The basic principles of current transport in metal-semiconductor (Schottky barrier) contacts are presented first. The modes of current transport considered are thermionic emission over the barrier, and tunneling through the barrier due to thermionic-field or field emission. Special attention is devoted to the parameters of temperature and doping concentration which determine the dominant mode of conduction. As the primary mode of conduction changes from thermionic emission dominated to tunneling dominated, the current-voltage behavior of the contact changes from rectifying to ohmic in character. The experimental techniques for fabricating ohmic contacts to III–V compound semiconductors are then described. Contact problems as they pertain to specific device applications are considered. Finally, present difficulties with contacts to mixed III–V crystals are discussed.

Heterostructure integrated thermionic coolers

Abstract: Thermionic emission in heterostructures is proposed for integrated cooling of high power electronic and optoelectronic devices. This evaporative cooling is achieved by selective emission of hot electrons over a barrier layer from the cathode to the anode. It is shown that with available high electron mobility and low thermal conductivity materials, and with optimized conduction band offsets in heterostructures, single-stage room temperature cooling of up to 20°–40° over thicknesses of the order of microns is possible.

Device model for single carrier organic diodes

Abstract: We present a unified device model for single layer organic light emitting diodes (LEDs) which includes charge injection, transport, and space charge effects in the organic material The model can describe both injection limited and space charge limited current flow and the transition between them We specifically considered cases in which the energy barrier to injection of electrons is much larger than that for holes so that holes dominate the current flow in the device Charge injection into the organic material occurs by thermionic emission and by tunneling For Schottky energy barriers less than about 03–04 eV, for typical organic LED device parameters, the current flow is space charge limited and the electric field in the structure is highly nonuniform For larger energy barriers the current flow is injection limited In the injection limited regime, the net injected charge is relatively small, the electric field is nearly uniform, and space charge effects are not important At smaller bias in the injection limited regime, thermionic emission is the dominant injection mechanism For this case the thermionic emissioninjection current and a backward flowing interface recombination current, which is the time reversed process of thermionic emission, combine to establish a quasi-equilibrium carrier density The quasi-equilibrium density is bias dependent because of image force lowering of the injection barrier The net device current is determined by the drift of these carriers in the nearly constant electric field The net device current is much smaller than either the thermionic emission or interface recombination current which nearly cancel At higher bias, injection is dominated by tunneling The bias at which tunneling exceeds thermionic emission depends on the size of the Schottky energy barrier When tunneling is the dominant injection mechanism, a combination of tunnelinginjection current and the backflowing interface recombination current combine to establish the carrier density We compare the model results with experimental measurements on devices fabricated using the electroluminescent conjugated polymer poly[2-methoxy, 5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] which by changing the contacts can show either injection limited behavior or space charge limited behavior

Tunneling versus thermionic emission in one-dimensional semiconductors.

Abstract: This Letter focuses on the role of contacts and the influence of Schottky barriers on the switching in nanotransistors. Specifically, we discuss (i) the mechanism for injection from a three-dimensional metal into a low-dimensional semiconductor, i.e., the competition between thermionic emission and thermally assisted tunneling, (ii) the factors that affect tunneling probability with emphasis on the importance of the effective mass for transistor applications, and (iii) a novel approach that enables determination of barrier presence and its actual height.