Potential and limits of superlattice multipliers coupled. Lashkaryov institute of semiconductor physics, nat. The work deals with the highly important problem of the qualitative temperature dependence of avalanche breakdown voltage in pn junctions based on 4hsic. Negative highfrequency differential conductivity in semiconductor superlattices. 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. Cui department of physics engineering physics, stevens institute of technology, hoboken, new jersey 07030 and k. 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. 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. Negative highfrequency differential conductivity in. Layerlike field inhomogeneities in homogeneous semiconductors in the range of nshaped negative differential conductivity. We examine the highfrequency differential conductivity response properties of semiconductor superlattices having various miniband dispersion laws.
Lateral surface superlattice having negative differential. Ibm journal of research and development 14 1, 6165, 1970. We analyze theoretically a superlattice structure proposed by a. Superlattice electrodynamics as a source of terahertz. If the period of a superlattice, of the order of 100a, is shorter than the electron mean. 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. They are in agreement with miniband transport and demonstrate superlattice negative differential conductance far in the millimetrewave domain. Semiconductorsuperlattice parametric oscillator as a.
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. It is shown that the presence of regions with a negative effective mass in a brillouin miniband is not necessary for ndc to. Negative differential conductivity in a confined superlattice. This type of conductivity is not infrequently found in semiconductors, where both factors that determine conductivitydensity of carriers and their mobility drift. Us7531850b2 semiconductor device including a memory cell. Chargecarriers propagating in superlattices exhibit the related phenomena known as negative differential conductivity and bloch oscillation. In this type the current is a single valued, continuous function of the voltage, but the voltage is a multivalued function of the current. Layerlike field inhomogeneities in homogeneous semiconductors.
Bloch oscillations and wannier stark ladder study in semiconductor superlattice. A semiconductor device may include at least one memory cell comprising a negative differential resistance ndr device and a control gate coupled thereto. Dynamics of electronic transport in spatiallyextended. The engineering of nanostructured materials with very low thermal conductivity is a necessary step toward the realization of efficient thermoelectric devices. Semiconductor superlattice theory and application introduction kai ni superlattice is a periodic structure of layers of two or more materials. Ndc exists even in superlattices with parabolic and superquadratic miniband dispersion relations, where the electron effective mass is positive. There are also other striking differences between physicals effects in graphene and common semiconductors, such as landau levels and hall conductivity. 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. 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. We consider a onedimensional periodic potential, or superlattice, in monocrystalline semiconductors formbeyd a periodic variation of alloy composition or of. As it has been shown before, the temperature coefficient of avalanche breakdown voltage tcabv is negative in seven sic polytypes, including 4sic. Watson research center, yorktown heights, nyj table showing the growth of research in superlattices and quantum wellsfrom 1972 to1986.
Pdf negative highfrequency differential conductivity in. The system is treated nonperturbatively in the illuminating field by employing local boundary conditions which allow the inclusion of asymmetric relaxation rates. Negative differential resistance and domain formation in. 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. Superlattice and negative differential conductivity in. In solidstate physics, the electron mobility characterises how quickly an electron can move. However, a strong enhancement in the current density intensity is observed in ndc of the achiral carbon nanotubes. On the nature of the negativeconductivity resonance in a. 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. 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.
Here we confirm the existence of gain and show that an optimized structure displays gain above 20 cm. Tsu communication superlattice and negative differential conductivity in semiconductors abstract. A theoretical study is presented to assess the performance of semiconductor superlattice multipliers as a function of the currently available input power sources. Millimetrewave negative differential conductance in. If a semiconductor has both electrons and holes, the total conductivity is. Wannierstark ladder and negative differential conductance. The resulting negative differential conductance in the device characteristics persists up to room temperature and is gate voltagetuneable due to graphenes unique diraclike spectrum. Superlattice and negative differential conductivity in semiconductors article pdf available in ibm journal of research and development 141. In this report, the standard transport theories for superlattices, i. Geometric and electronic structure of a semiconductor. This ndr is found only in one bias polarity and is not found when the bias is reversed, which is. The oscillator is driven by a microwave source frequency near 100 ghz. In this work, the dependence of the drift velocity and displacement of chargecarriers on external, applied electric fields is investigated. A novel multistate sshaped negative differential conductivity ndc.
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. Applying the insight into superlattice and quantum wells for nanostructures. Superlattice and negative differential conductivity in semiconductors free download as pdf file. A simple admittance model for negative differential conductance devices accounts for the results in both experimental approaches. Superlattice and negative differential conductivity in semiconductors abstract. Pdf superlattice and negative differential conductivity. Superlattice and negative differential conductivity in semiconductors. As shown in the figure below, it is a superlattice formed by. Typically the width of layers is orders of magnitude larger than the lattice constant, and is limited by the growth of the structure1. Electric transport in semiconductor superlattices is dominated by pronounced negative differential conductivity. Among all the ndc effects, periodical ndc is one of the most special ones. The prime devices which are considered as input power sources are impatt diodes, inp gunn devices, superlattice electron devices and backward wave oscillator sources. On the differential conductivity of semiconductor superlattices on the differential conductivity of semiconductor superlattices romanov, yu.
Thornber nec research institute, 4 independence way, princeton, new jersey 08540 received january 1993 by a. Negative differential resistance ndr is observed at around 85 k. Voltage controlled negative resistance vcnr, shortcircuit stable, or n type. Carrier dynamics in semiconductors studied with timeresolved terahertz spectroscopy pdf. Resonant tunnelling and negative differential conductance. We also present an analysis indicating that operation at frequencies above 1 thz should be possible. The nature of negative differential conductivity ndc of a semiconductor superlattice was studied. While group iiiv semiconductors especially gaasal x ga 1. Shot noise in negativedifferentialconductance devices. Fabrication of a chirp coherent heterointerfaces for reflection and penetration superlattice device is presented. This behaviour may be utilised for the generation of tunable electromagnetic radiation. A negative differential conductivity ndc is predicted in quasistatic approximation i.
Tunnelling and negative resistance phenomena in semiconductors. Semiconductor materials, which are used to fabricate the superlattice structures, may be divided by the element groups, iv, iiiv and iivi. Their relation to each other is clarified by a comparison with a quantum transport model based on nonequilibrium. Esaki and tsu1 have proposed that a semiconductor superlattice a periodically repeated arrangement of alternating layers of two iiiv semiconductors might exhibit negative differential. We consider a onedimensional periodic potential, or superlattice, in. The physics, technology, and circuitry of semiconductor negative resistance devices are. Theoretical model for negative differential conductance in 2d. The multistate ndc originates from a sequential subavalanche multiplication in the superlattice periods.
In this report the standard transport theories for superlattices, i. The conditions for absolute negative conductivity and for the spontaneous generation of a significant static electric field are determined. We analyze the transport properties of a semiconductor superlattice in the presence of a biharmonic electric field. Citeseerx document details isaac councill, lee giles, pradeep teregowda. We describe the operation of a semiconductor superlattice parametric oscillator spo at a subterahertz frequency near 300 ghz. Superlattice gain in positive differential conductivity. 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. 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. On the nature of the negative conductivity resonance in a superlattice bloch oscillator herbert kroemer ece department, university of california, santa barbara, ca 93106. The spo is based on the ability of conduction electrons in a superlattice to perform bloch. 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.
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