Switching and negative capacitance in Al-Ge15Te81Sb2S2-Al devices
TL;DR: In this article, a theory to explain the switching behavior and variation of the capacitance with temperature and voltage, is proposed for vacuum evaporated metal-glass-metal devices, and it is also shown that the observed capacitance of the device could be negative under voltage bias conditions.
Abstract: A theory to explain the switching behaviour and variation of the capacitance with temperature and voltage, is proposed for vacuum evaporated metal-glass-metal devices. It is also shown that the observed capacitance of the device could be negative under voltage bias conditions. It is proposed that the voltage Vth at which the device changes from the off state to the on state and the transition voltage Vcn at which the capacitance of the device becomes negative should be related to the glass transition temperature Tg. A study of Al-Ge15Te81Sb2-Al devices reveals that the experimental results are in concurrence with the theoretical predictions.
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TL;DR: In this paper, the negative capacitance effect in quantum well infrared photodetectors (QWIPs) has been investigated theoretically and confirmed experimentally by simulation results and experimental studies.
Abstract: Nontrivial capacitance behavior, including a negative capacitance (NC) effect, observed in a variety of semiconductor devices, is discussed emphasizing the physical mechanism and the theoretical interpretation of experimental data. The correct interpretation of NC can be based on the analysis of the time-domain transient current in response to a small voltage step or impulse, involving a self-consistent treatment of all relevant physical effects (carrier transport, injection, recharging, etc.). NC appears in the case of the nonmonotonic or positive-valued behavior of the time-derivative of the transient current in response to a small voltage step. The time-domain transient current approach is illustrated by simulation results and experimental studies of quantum well infrared photodetectors (QWIPs). The NC effect in QWIPs has been predicted theoretically and confirmed experimentally. The huge NC phenomenon in QWIP's is due to the nonequilibrium transient injection from the emitter caused by the properties of the injection barrier and the inertia of the QW recharging.
279 citations
Additional excerpts
...The NC effect has been displayed by a variety of electronic devices, both heterostructures and homostructures, made of crystalline or amorphous semiconductors, such as Si, Ge, GaAs, HgCdTe, Se, and others [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38]....
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TL;DR: In this paper, the authors investigated the high-frequency switching behavior of negative-capacitance FETs using the Landau-Khalatnikov equation to model ferroelectric materials.
Abstract: Recently, negative-capacitance FETs (NCFETs) have been proposed to reduce subthreshold slope and help continue supply-voltage scaling alongside channel-length scaling. We investigate the high-frequency switching behavior of NCFETs using the Landau–Khalatnikov equation to model ferroelectric materials. Multidomain interactions in the ferroelectric are considered, resulting in strong agreement with experimental measurements. Operation of NCFETs at gigahertz frequencies is investigated with this experimentally validated multidomain model. We find that the effectiveness of the voltage amplification in NCFETs is strongly dependent on the viscosity coefficient $\rho $ of the ferroelectric, and that a low $\rho $ ( $ ) is required for the operation at the high gigahertz frequencies.
63 citations
TL;DR: In this article, the importance of parasitic series inductance at low frequencies when device conductance is large, such as in a forward biased Schottky barrier, or when large device leakage currents are present.
Abstract: A number of authors make reference to “negative capacitances” observed during impedance measurements of metal-semiconductor and other semiconductor device structures at sufficiently low frequencies for parasitic inductances to be assumed negligible. Often, these negative capacitances are attributed to physical phenomena associated with the devices being measured. It is demonstrated in this paper that many such interpretations incorrectly neglect the importance of parasitic series inductances at low frequencies when device conductance is large, as in a forward biased Schottky barrier, or when large device leakage currents are present. Simulations of experimental data for a Schottky diode show that typical values of probe lead and other instrumental inductance may be sufficient to provide an instrumental explanation for the apparent effect.
49 citations
TL;DR: In this article, an experimental investigation was carried out on the kinetic nature of the set process in a phase change memory device by combined analyses of set voltage wave forms and time-resolved low-field resistances.
Abstract: An experimental investigation was carried out on the kinetic nature of the set process in a phase change memory device by combined analyses of set voltage wave forms and time-resolved low-field resistances. As it turned out, the progress of a set process may be measured in terms of three characteristic times in sequence i.e., threshold switching time tth, incubation time for crystallization tinc, and complete set time tset. These characteristic times are supposed to demarcate, in some measure, different stages of crystallization in the memory material during a set process. Each of these times has a strong dependence on input pulse voltage and particularly threshold switching time tth was found to have an exponentially decaying dependence. The latter may be related to the decreasing capacitance of an amorphous phase-change material with approaching threshold switching.
29 citations
TL;DR: In this article, the negative capacitance effect in quantum well infrared photodetectors (QWIPs) has been investigated theoretically and confirmed experimentally by simulation results and experimental studies.
Abstract: Nontrivial capacitance behavior, including a negative capacitance (NC) effect, observed in a variety of semiconductor devices, is discussed emphasizing the physical mechanism and the theoretical interpretation of experimental data. The correct interpretation of NC can be based on the analysis of the time-domain transient current in response to a small voltage step or impulse, involving a self-consistent treatment of all relevant physical effects (carrier transport, injection, recharging etc.). NC appears in the case of the non-monotonic or positive-valued behavior of the time-derivative of the transient current in response to a small voltage step. The time-domain transient current approach is illustrated by simulation results and experimental studies of quantum well infrared photodetectors (QWIPs). The NC effect in QWIPs has been predicted theoretically and confirmed experimentally. The huge NC phenomenon in QWIPs is due to the non-equilibrium transient injection from the emitter caused by the properties of the injection barrier and the inertia of the QW recharging.
26 citations
References
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TL;DR: In this paper, it was shown that all germanium junctions break down as the result of the same avalanche process found in silicon, and an empirical expression for the multiplication inherent in this breakdown process was given for step junctions.
Abstract: It is shown that all germanium junctions studied break down as the result of the same avalanche process found in silicon. An empirical expression for the multiplication inherent in this breakdown process is given for step junctions. Ionization rates for holes and electrons in Ge are derived with the use of this expression. The ionization rate for holes is larger than that for electrons by about a factor of two. The agreement between these ionization rates as a function of field and the theory of Wolff is excellent. It is determined that the threshold for electron-hole pair production is about 1.50 ev and the mean free path for electron (or hole)-phonon collisions is about 130 A.
320 citations
TL;DR: The performance and reliability of amorphous semiconductor devices that deal with the handling of information in the form of switching, modulation, storage, and display are discussed in this article.
Abstract: Performance and reliability of amorphous semiconductor devices that deal with the handling of information in the form of switching, modulation, storage, and display are discussed. Structural changes between a disordered and a more ordered state and the concomitant large change in many material properties offer the possibility of using amorphous semiconductors for high-density information storage and high-resolution display devices. The structural changes can be initiated by various forms of energy such as an electrical pulse, a short light pulse, or a brief light exposure. Many materials show good structural reversibility. The sensitivity of an amorphous photostructural film is amplified by several orders of magnitude by first forming a latent image by photonucleation and subsequent dry development by heat or radiation. Examples of optical contrast and resolution in image formation are given. The major differences between crystalline and amorphous semiconductors are briefly outlined.
229 citations
TL;DR: In this paper, experimental evidence is presented bearing on the low current conduction and on the rapid electrical switching phenomena that have been found in thin films of certain amorphous chalcogenide semiconducting materials.
Abstract: : Experimental evidence is presented bearing on the low current conduction and on the rapid electrical switching phenomena that have been found in thin films of certain amorphous chalcogenide semiconducting materials. The principal findings are that (1) the low current conduction consists of an 'ohmic' region linear with voltage and an exponentially varying nonlinear region, both of which arise from the same conduction process; (2) at voltages just below switching, the equivalent parallel capacitance of the film becomes negative; and (3) a field-influenced dielectric phase transition is implicated in the switching process. The phase transition temperature appears to be related to the glass transition temperature. (Author)
111 citations
TL;DR: In this paper, the variation in capacitance of amorphous materials was evaluated as a function of temperature and electric field in the high-resistance state, and it was shown that at low temperatures, and at fields near the threshold of switching for higher temperatures, the incremental ac capacitance becomes negative.
Abstract: Certain amorphous materials exhibit rapid electrical switching. The variation in their capacitance was evaluated as a function of temperature and electric field in the high‐resistance state. The zero‐field capacitance follows a Curie‐Weiss law above room temperature. At low temperatures, and at fields near the threshold of switching for higher temperatures, the open‐circuit incremental ac capacitance becomes negative.
34 citations
TL;DR: In this paper, the authors developed the theory of ac electrical properties in MIM systems in which Schottky barriers are assumed to exist at the metal-insulator interface, and the resulting capacitance and conductance vs frequency, temperature, and voltage bias are shown to exhibit all the salient features of the observed data, suggesting that such a model is more applicable than the Debye model.
Abstract: In the past, ac properties obtained from thin‐film metal‐insulator‐metal (MIM) samples have often been analyzed qualitatively in terms of the Debye relaxation process. Here we point out several anomalies and discrepancies associated with these analyses. We then go on to develop the theory of ac electrical properties in MIM systems in which Schottky barriers are assumed to exist at the metal‐insulator interface. The resulting capacitance and conductance vs frequency, temperature, and voltage bias are shown to exhibit all the salient features of the observed data, suggesting that such a model is more applicable than the Debye model, at least in the case of the materials reviewed.
34 citations