Multiple negative-differential-resistance (MNDR) phenomena of ametal-insulator-semiconductor-insulator-metal (MISIM)-like structurewith step-compositioned InxGa1-xAs quantum wells

In this paper, a new multiple negative-differential-resistance (MNDR) device based on a metal-insulator-semiconductor-insulator-metal (MISIM)-like structure with step-compositional In_xGa_1-x As quantum wells has been fabricated and demonstrated. The interesting MNDR phenomena are found in the current-voltage (I-V) characteristics of this device. At room temperature, the triple switching behaviours and quadruple stable operation states are obtained. In addition, the sixfold switching behaviors and a staircase-shaped I-V characteristic are observed at -105°C. A sequential carrier accumulation at InGaAs subwells and the potential lowering process are used to qualitatively explain the interesting MNDR phenomena. From the experimental results, it is shown that the studied device has good potential in multiple-valued logic applications     

Observation of the multiple negative-differential-resistance ofmetal-insulator-semiconductor-like structure with step-compositioned InxGa1-xAs quantum wells

An interesting multiple negative-differential-resistance (MNDR) device, based on an AlGaAs-InGaAs-GaAs metal-insulator-semiconductor (MIS)-like structure, has been fabricated and demonstrated. Three and six switching phenomena have been observed at room temperature and -105°C, respectively. The impressive MNDR behaviors are believed to be caused by the sequential accumulation process of carriers at In_x Ga_1-xAs subwells and the successive barrier lowering and potential redistribution effects. These effects yield the step by step enhancement of tunneling through the “insulated” AlGaAs barrier. It is known that, from experimental results, the temperature variation plays an important role on carriers transport and experimental current-voltage (I-V) characteristics     

Multiple negative-differential-resistance (NDR) of InGaP/GaAsheterostructure-emitter bipolar transistor (HEBT)

An interesting multiple S-shaped negative-differential-resistance (NDR) phenomenon is observed for an InGaP/GaAs heterostructure-emitter bipolar transistor (HEBT) under the inverted operation mode. This behavior results from a sequential avalanche multiplication and two-stage barrier lowering effect. The two-stage barrier lowering effect is assumed to be caused by the high valence-band-discontinuity (ΔE _v) to conduction-band-discontinuity (ΔE_c) ratio at InGaP/GaAs heterointerface which gives holes and electrons accumulation effect successively. Under normal operation mode, a typical common-emitter current gain of 60 is obtained at collector current density of 400 A/cm² for the studied HEBT without emitter-edge thinning structure. Consequently, the controlled switching and transistor performances provide a promise of the studied device for circuit applications     

Multiple-route current-voltage (I-V) characteristics of GaAs-InGaAsmetal-insulator-semiconductor-like (MIS) structure for multiple-valuedlogic applications

A new GaAs-In_xGa_1-xAs metal-insulator-semiconductor-like (MIS) device with the interesting dual-route and multiple-negative-differential-resistance (MNDR) current-voltage (I-V) characteristics has been fabricated and demonstrated. These performances are caused by the successive barrier lowering and potential redistribution effect. A novel multiple-route I-V characteristic is obtained in the studied device at low temperature (-130°C). This performance is different from the previously reported NDR switching device and has not yet been found in other devices. The interesting property of the studied structure provides a promising candidate for switching device applications     

A novel InGaP/GaAs S-shaped negative-differential-resistance (NDR)switch for multiple-valued logic applications

In this paper, a novel InGaP/GaAs multiple S-shaped negative-differential-resistance (NDR) switch based on a heterostructure-emitter bipolar transistor (HEBT) structure is fabricated and demonstrated. An interesting multiple NDR phenomenon resulting from an avalanche multiplication and successive two-stage barrier lowering process is observed under the inverted operation mode. The three-terminal-controlled and temperature-dependent NDR characteristics are also investigated. In addition, a typical transistor performance is found under the normal operation mode. Consequently, owing to the presented different stable operation points and transistor action, the studied device shows a good potential for multiple-valued logic and analog amplification circuit applications     

High-power punch-through avalanche-diode microwave oscillators

Two distinctive modes of oscillation are observed in specially profiled silicon avalanche diodes: transit-time mode at 3 to 7 GHz at lower bias current densities and an anomalous mode at around 1 GHz above certain threshold current levels. High pulsed power has been produced from both modes of operation. Space-charge-induced negative resistances are computed and their dependence on device parameters are discussed. Experimentally observed correlations between these two modes, including a locking behavior of the anomalous mode by the transit-time mode, and the computed and observed slight negative resistance at the anomalous-mode threshold suggest that the transit- time-mode oscillation and the space-charge-induced negative resistance are two possible pre-requisites for the initiation of the anomalous mode of oscillation.     

An optoelectronic switch based on a triangular-barrier structure

A GaAs-InGaP triangular-barrier optoelectronic switch, grown by metalorganic chemical vapor deposition (MOCVD), is reported in the paper. Owing to the avalanche multiplication and hole confinement in the device operation, S-shaped negative-differential-resistance (NDR) performances are observed in the current-voltage (I-V) characteristics under both normal and reverse operation modes. The device also showed a flexible optical function related to the potential barrier height controllable by incident light. The dependency of the carrier transport mechanism on illumination, as well as the I-V characteristics at different temperatures, are investigated     

Hot-electron-induced interface state generation in n-channel MOSFET's at 77 K

Hot-electron-induced degradation in n-channel Si MOSFET's as a result of stress voltages applied at 77 K was studied. The devices were stressed at 77 K for 48 h with a drain voltage of 5 V and a gate voltage corresponding to that at which maximum substrate current was measured. Comparison of pre-stress and post-stress electrical characteristics for forward and for inverse mode operation at room temperature and at 77 K indicate that the observed degradation was due to the generation of hot-electron-induced acceptor interface states at the drain end of the device approximately 0.09 eV below the Si conduction band edge. No trapped charge resulting from hot-electron injection into the gate oxide was observed. The charge associated with the filled interface states had no observable effect on effective channel electron mobility at room temperature, and reduced that at 77 K by no more than 25 percent of the pre-stress value. Operation of CMOS inverters in either logic state (OFF, ON) resulted in no degradation of either device. Operation in a switching mode at 77 K did result in degradation of the n-channel device but not the p-channel FET. The observed degradation is thought to be correlated with the substrate current generated during the switching transient.     

A double-barrier-emitter triangular-barrier optoelectronic switch

In this study, a triangular-barrier and a double-barrier structure are combined to form a double-barrier-emitter triangular-barrier optoelectronic switch (DTOS). In the structure center of the triangular barrier, a p-type delta-doped quantum well is inserted to enhance the hole confinement. Owing to the resonant tunneling through the double-barrier structure and avalanche multiplication in the reverse-biased junction, N-shaped and S-shaped negative-differential-resistance (NDR) phenomena occur in the current-voltage (I--V) characteristics under normal and reverse operation modes, respectively. The NDR characteristics show variations from dark to illumination conditions. Temperature effects on the NDRs of the DTOS are also obvious. The illumination and temperature influences on the device characteristics are investigated in this paper.     

The dual gate power device exhibiting the IGBT and the thyristoraction

This new power device is fabricated and demonstrated for the first time. The device can behave as an insulated gate field-effect transistor (IGBT) or a thyristor by adding a second control gate. The characteristics obtained experimentally are that the forward voltage for the thyristor mode is 1.2 V at 100 A/cm², the device transits between two operation modes within only 200 ns, and the switching speed for the IGBT mode is the same as the usual IGBT. All these results indicate that the trade-off relation between the forward voltage and switching speed was greatly improved by the additional gate