We report here the main results of an investigation with nonequilibrium molecular dynamics simulations on thermal transport in sige superlattice nanowires aiming at taking advantage of the inherent one dimensionality and the. Typically the width of layers is orders of magnitude larger than the lattice constant, and is limited by the growth of the structure1. Reona esaki esaki reona, born march 12, 1925, also known as leo esaki, is a japanese physicist who shared the nobel prize in physics in 1973 with ivar giaever and brian david josephson for his work in electron tunneling in semiconductor materials which finally led to his invention of the esaki diode, which exploited that phenomenon this research was done when he was with. A simple admittance model for negative differential conductance devices accounts for the results in both experimental approaches.
The resulting negative differential conductance in the device characteristics persists up to room temperature and is gate voltagetuneable due to graphenes unique diraclike spectrum. Shot noise in negativedifferentialconductance devices. Semiconductorsuperlattice parametric oscillator as a. We examine the highfrequency differential conductivity response properties of semiconductor superlattices having various miniband dispersion laws. On the differential conductivity of semiconductor superlattices on the differential conductivity of semiconductor superlattices romanov, yu. This type of conductivity is not infrequently found in semiconductors, where both factors that determine conductivitydensity of carriers and their mobility drift. As it has been shown before, the temperature coefficient of avalanche breakdown voltage tcabv is negative in seven sic polytypes, including 4sic. Dynamics of electronic transport in spatiallyextended. In this work, the dependence of the drift velocity and displacement of chargecarriers on external, applied electric fields is investigated. Negative differential resistance ndr is observed at around 85 k. In this type the current is a single valued, continuous function of the voltage, but the voltage is a multivalued function of the current. The work deals with the highly important problem of the qualitative temperature dependence of avalanche breakdown voltage in pn junctions based on 4hsic. In solidstate physics, the electron mobility characterises how quickly an electron can move. Voltage controlled negative resistance vcnr, shortcircuit stable, or n type.
This ndr is found only in one bias polarity and is not found when the bias is reversed, which is. Geometric and electronic structure of a semiconductor. This type of conductivity is not infrequently found in semiconductors, where both factors that determine conductivity density of carriers and their mobility drift velocity developed per unit fieldmay. The system is treated nonperturbatively in the illuminating field by employing local boundary conditions which allow the inclusion of asymmetric relaxation rates. Lateral surface superlattice having negative differential. Cui department of physics engineering physics, stevens institute of technology, hoboken, new jersey 07030 and k. Negative differential resistances can be classified into two types. They are in agreement with miniband transport and demonstrate superlattice negative differential conductance far in the millimetrewave domain.
Ndc negative differential conductivity ftir fourier transform infrared spectroscopy. In this paper with solve the boltzmannbloch equation within a path integral approach, delivering general, nonperturbative solutions of high harmonic generation in semiconductor superlattices with asymmetric current flow. A novel multistate sshaped negative differential conductivity ndc. Thornber nec research institute, 4 independence way, princeton, new jersey 08540 received january 1993 by a. As shown in the figure below, it is a superlattice formed by. Here we confirm the existence of gain and show that an optimized structure displays gain above 20 cm. There are also other striking differences between physicals effects in graphene and common semiconductors, such as landau levels and hall conductivity. Negative differential resistance and domain formation in.
However, a strong enhancement in the current density intensity is observed in ndc of the achiral carbon nanotubes. The oscillator is driven by a microwave source frequency near 100 ghz. Ndc exists even in superlattices with parabolic and superquadratic miniband dispersion relations, where the electron effective mass is positive. Superlattice and negative differential conductivity in semiconductors article pdf available in ibm journal of research and development 141. We consider a onedimensional periodic potential, or superlattice, in. If a semiconductor has both electrons and holes, the total conductivity is. We consider a onedimensional periodic potential, or superlattice, in monocrystalline semiconductors formed by a periodic variation of alloy composition or of impurity density introduced during epitaxial growth. While the noise spectral density of the former device was greatly enhanced over the poissonian value of 2ei in the ndc region, that of the latter device remained 2ei. A semiconductor device may include at least one memory cell comprising a negative differential resistance ndr device and a control gate coupled thereto.
Superlattice and negative differential conductivity in semiconductors. Ibm journal of research and development 14 1, 6165, 1970. Chargecarriers propagating in superlattices exhibit the related phenomena known as negative differential conductivity and bloch oscillation. On the nature of the negativeconductivity resonance in a. Carrier dynamics in semiconductors studied with timeresolved terahertz spectroscopy pdf. Pdf negative highfrequency differential conductivity in. The conditions for absolute negative conductivity and for the spontaneous generation of a significant static electric field are determined. Our analysis shows that the anharmonicity of bloch oscillations beyond tightbinding approximation leads to the occurrence of negative highfrequency differential conductivity at frequency multiples of the bloch frequency. Resonant tunnelling and negative differential conductance. While group iiiv semiconductors especially gaasal x ga 1. Superlattice electrodynamics as a source of terahertz. Watson research center, yorktown heights, nyj table showing the growth of research in superlattices and quantum wellsfrom 1972 to1986. Layerlike field inhomogeneities in homogeneous semiconductors.
Our analysis shows that the anharmonicity of bloch oscillations beyond tightbinding approximation leads to the occurrence of negative highfrequency differential. In this report, the standard transport theories for superlattices, i. The engineering of nanostructured materials with very low thermal conductivity is a necessary step toward the realization of efficient thermoelectric devices. In this report the standard transport theories for superlattices, i.
Millimetrewave negative differential conductance in. It is shown that the presence of regions with a negative effective mass in a brillouin miniband is not necessary for ndc to. A negative differential conductivity ndc is predicted in quasistatic approximation i. N a semiconductor situated in a strong electric field, the currentvoltage characteristic j e have a section with negative differential conductivity ud superlattice with high electron mobility and an unusual electronic dispersion whose miniband edges and saddle points can be reached by electrostatic gating. U nique electrical behavior results when a system operates in a region of negative differential conductivity, where current density falls rather than rises with increasing electric fields. Superlattice and negative differential conductivity in semiconductors abstract. Esaki and tsu1 have proposed that a semiconductor superlattice a periodically repeated arrangement of alternating layers of two iiiv semiconductors might exhibit negative differential.
Wannierstark ladder and negative differential conductance. Tsu communication superlattice and negative differential conductivity in semiconductors abstract. Fabrication of a chirp coherent heterointerfaces for reflection and penetration superlattice device is presented. We analyze theoretically a superlattice structure proposed by a. We describe the operation of a semiconductor superlattice parametric oscillator spo at a subterahertz frequency near 300 ghz.
Pdf superlattice and negative differential conductivity. Applying the insight into superlattice and quantum wells for nanostructures. On the nature of the negative conductivity resonance in a superlattice bloch oscillator herbert kroemer ece department, university of california, santa barbara, ca 93106. Negative differential conductivity ndc is a nonlinear property of electronic transport for high electric field strength found in materials and devices such as semiconductor superlattices, bulk. The ndr device may include a superlattice including a plurality of stacked groups of layers, with each group of layers of the superlattice including a plurality of stacked base semiconductor monolayers defining a base semiconductor portion. Negative di erential conductivity ndc is a nonlinear property of electronic trans port for high electric eld strength found in materials and devices such as semiconduc tor. The multistate ndc originates from a sequential subavalanche multiplication in the superlattice periods. Layerlike field inhomogeneities in homogeneous semiconductors in the range of nshaped negative differential conductivity. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Theoretical model for negative differential conductance in 2d. Bloch oscillations and wannier stark ladder study in.
Potential and limits of superlattice multipliers coupled. Tunnelling and negative resistance phenomena in semiconductors. Electric transport in semiconductor superlattices is dominated by pronounced negative differential conductivity. We consider a onedimensional periodic potential, or superlattice, in monocrystalline semiconductors formbeyd a periodic variation of alloy composition or of. Instability in semiconductor material is frequently related to the occurrence of negative differential conductivity ndc, which has proven to be very useful in the generation, amplification, switching and processing of microwave signals. Superlattice and negative differential conductivity in. Among all the ndc effects, periodical ndc is one of the most special ones. The study of superlattices and observations of quantum mechanical effects on a new physical scale may provide a valuable area of investigation in the fieid of. Semiconductor materials, which are used to fabricate the superlattice structures, may be divided by the element groups, iv, iiiv and iivi. Negative differential conductivity in a confined superlattice. We analyze the transport properties of a semiconductor superlattice in the presence of a biharmonic electric field. The physics, technology, and circuitry of semiconductor negative resistance devices are. The spo is based on the ability of conduction electrons in a superlattice to perform bloch. Superlattice gain in positive differential conductivity.
If the period of a superlattice, of the order of 100a, is shorter than the electron mean. We also present an analysis indicating that operation at frequencies above 1 thz should be possible. Lashkaryov institute of semiconductor physics, nat. The prime devices which are considered as input power sources are impatt diodes, inp gunn devices, superlattice electron devices and backward wave oscillator sources. Bloch oscillations and wannier stark ladder study in semiconductor superlattice. It is shown that the presence of regions with a negative effective mass in a brillouin miniband is not necessary for ndc to set in. This behaviour may be utilised for the generation of tunable electromagnetic radiation.
Negative highfrequency differential conductivity in semiconductor superlattices. The nature of negative differential conductivity ndc of a semiconductor superlattice was studied. Semiconductor superlattice theory and application introduction kai ni superlattice is a periodic structure of layers of two or more materials. Negative highfrequency differential conductivity in. This invention relates to semiconductor devices and more particularly to a lateral surface superlattice device having electronically created quantum wells and which exhibits negative differential conductivity due to bloch oscillations as well as to a processes for producing same. This effect has been explained by the wannierstark localization wsl. Superlattice and negative differential conductivity in semiconductors free download as pdf file. The modification of currentvoltage characteristics induced by the biharmonic radiation is obtained.
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