Fully integrated 1.2-μA and 13-μA quiescent current LDOs with improved transient response

We introduce two extremely low quiescent current (I _Q ) low-dropout (LDO) voltage regulators. The Low I _Q -LDO (LI _Q -LDO) uses 13 μA of total quiescent current and is designed for a maximum load current of 50 mA. The Micro I _Q -LDO (MI _Q -LDO) uses only 1.2 μA of total quiescent current and is designed for a maximum load current of 5 mA. Detailed pole/zero analysis is performed to aid in the design of the LDOs. Two LHP zeros cancel the two non-dominant poles which extend the bandwidth and improve transient response. Both designs are fully integrated, stabilized with an on-chip capacitive load of 100 pF. In load transient, the total variation in output voltage for LI _Q -LDO and MI _Q -LDO is 1 V and 950 mV, respectively, and the total line transient variation is 668 and 599 mV, respectively. Both designs occupy an area of 0.26 mm² in a 0.5-μm CMOS process. Two process-independent figures of merit are proposed to compare LI _Q -LDO and MI _Q -LDO with other published work.     

Multistability and synchronization of chaos in maps with “Internal” coupling

Bifurcation mechanisms responsible for the loss of the complete synchronization of chaos and for formation of multistability in a system with a unidirectional “internal” coupling are considered. The sequence of stages during which chaotic synchronization decays is described. A quantitative analysis of chaotic synchronization is performed.     

Theory of tunneling current in metal-semiconductor contacts with subsurface isotype δ-doping

The theory of tunneling current in metal-semiconductor contacts with subsurface isotype δ-doping is developed. Analytical expressions for current that take into account the decrease in the potential barrier height due to the image forces are obtained using the Murphy-Good approach. Characteristics of δ-doping that provide effective thermal field emission at the metal-semiconductor contact and a decrease in the effective barrier height from the original value to several kT are calculated. It is established that the main voltage dependence of the current in a contact with isotype δ-doping is exponential. It is shown that the nonideality factor can remain small (n≤1.07) for all values of the barrier height. A dramatic increase in n to the values n≥1.5 is typical of contacts with a partially depleted layer.     

Electric and magnetic optical polaron in quantum dot——Part 1: strong coupling

We investigated the influence of electric field and magnetic field on the ground state energy of polaron in spherical semiconductor quantum dot (QD) using a modified Lee Low Pines (LLP) method. The numerical results show the increase of the ground state energy with the increase of the electric field and the decreasing with the magnetic field. The modulation of the electric field, magnetic field and the confinement lengths lead to the control of the decoherence of the system.     

On the current transport mechanism in a metal—insulator—semiconductor (MIS) diode

The current transport mechanism in an MIS-tunnel diode has been studied by considering both the process of tunneling and the effect of pinholes in the insulating layer. It has been shown that in order to explain the experimental J-V characteristics of MIS-diodes, presence of a thin interfacial layer of thickness δ_p within the pinholes should be considered. From an analysis of the tJ-V and C-V characteristics, a method has been suggested for the estimation of the value of δ_p. The values of interface trap density and barrier height for the MOS-part of the diodes are also calculated. The dependence of barrier height on oxide thickness for the diodes is found to obey the barrier height model of Cowley and Sze.     

A curvature calibrated bandgap reference with base-emitter current compensating in a 0.13μm CMOS process

In bandgap references,the effect caused by the input offset of the operational amplifier can be effectively reduced by the utilization of cascade bipolar junction transistors(BJTs).But in modern CMOS logic processes,due to the small value ofβ,the base-emitter path of BJTs has a significant streaming effect on the collector current,which leads to a large temperature drift for the reference voltage.To solve this problem,a base-emitter current compensating technique is proposed in a cascade BJT bandgap refe...     

Magnetoabsorption of the electromagnetic radiation by a two-dimensional electron gas with Rashba’s spin-orbit coupling in a heterojunction with a lateral superlattice

Absorption of linearly polarized electromagnetic radiation by a two-dimensional electron gas in a lateral-superlattice structure subjected to a perpendicular magnetic field is calculated analytically and numerically for the first time, taking into account Rashba’s spin-orbit coupling and Zeeman splitting. Calculations are carried out for semiconductor heterostructures characterized by weak and sufficiently strong spin-orbit coupling (AlGaAs/GaAs and GaAs/InGaAs, respectively). The nature of the new effect related to intense magnetoabsorption of electromagnetic radiation in the submillimeter range by a two-dimensional electron gas in a superlattice with strong spin-orbit coupling is analyzed. Magneto-optical experiments aimed at studying spin-Peierls states of charge carriers are discussed and, in this context, optimum parameters for semiconductor structures with spin-orbit coupling and values of the magnetic field are determined.     

A zero-crossing based 10-bit 100 MS/s pipeline ADC with controlled current in 90 nm CMOS

In this paper, a new charging technique for low power zero-crossing based circuit pipeline analog-to-digital converters (ADCs) is presented. The charging current sources are implemented as voltage-controlled current sources in order to charge the sampling capacitors based on the error signal. Using this method, the ADC power consumption is reduced while improving the accuracy. The necessary current control block is shared between consecutive stages further reducing the power consumption and die area. The proposed technique is applied to a 10-bit 100 MS/s pipeline ADC designed in a 90 nm CMOS technology with 1 V power supply. Circuit level simulation results using Cadence Spectre show a signal-to-noise and distortion ratio of 55.6 dB with 3.56 mW power consumption resulting in a figure of merit of 72.3 fJ/conv.step without employing any calibration technique.     

AEETC—adaptive energy-efficient timing control in wireless networks with network coding

Energy is a scarce resource in wireless networks. Network coding has been proposed recently as a means to reduce the number of transmissions and energy consumption. In this paper, we introduce timing control into network coding to further enhance its performance. It is found that when bandwidth is sufficient, the extra delay introduced by waiting for additional data to perform network coding will increase the number of codings without affecting system throughput. Both delay and throughput suffers when bandwidth is insufficient. An adaptive energy-efficient timing control algorithm called AEETC is proposed which can automatically adjust local node’s transmission behavior on the basis of the network traffic conditions. Simulation results demonstrate that AEETC increases network coding by 7% to 60% for light network load and is able to provide good performance in terms of delay, throughput and the number of successful codings.     

The spread of cross section for electron capture by a trap with a discrete energy level in γ-La2S3 crystals

The data on a new phenomenon (a formation of the range of values for an electron-capture cross section) are reported by the example of an electron trap with a discrete level of E _c -0.2 eV in γ-La₂S₃ crystals; the data were obtained by employing the thermally stimulated luminescence. The range of variations in the cross section is as large as four orders of magnitude (10^?23–10^?19 cm²). A model, according to which the electron trap at E _c -0.2 eV is a donor involved in the donor-acceptor pairs distributed in interatomic distances and localized in the vicinity of a negatively charged dislocation, is suggested. It is shown that the formation of a range of electron-capture cross sections is a result of a spread of the cross-section modulation factor at points with different values of potential of the dislocation electric field.     

OMH—Suppressing Selfish Behavior in Ad hoc Networks with One More Hop

In ad hoc networks, wireless nodes rely on each other to transmit data over multi-hops by forwarding packets. A selfish node may decide not to forward packets for other nodes to save its own resource but still use the network to send and receive data. Such a selfish behavior can degrade network performance significantly. Most existing work took observation, reputation and token based mechanisms. However observation based mechanism suffers from mobility and collusion; reputation and token based mechanisms suffer from system complexity and efficiency. In this paper, we propose One More Hop (OMH) protocol which suppresses selfish behavior from a totally new angle. Basing on the fact that the selfish but rational nodes still want to receive and send packets, if a node can not determine whether a packet is destined for it or not, it can not drop the packet. With modified routing protocol and cryptographic techniques, OMH achieves this design target. It is robust and efficient. The simulation shows that OMH works well under different network situations.     

Transport in GaAs/Al x Ga1−x As superlattices with narrow forbidden minibands: Low-frequency negative differential conductivity and current oscillations

Semiconductors - Current-voltage characteristics have been measured and low-frequency current instabilities have been studied for GaAs/Al x Ga1?x As superlattices with narrow forbidden...     

Nature of forward and reverse saturation currents in metal—semiconductor contacts with the Schottky barrier

The heavy dependence of the saturation currents for the forward and reverse I–V characteristics of high-barrier (>0.6 V) metal-semiconductor cont acts with the Schottky barrier on their diameter D is determined by an additional electric field formed under the effect of the contact periphery; this field is built into and codirected with the intrinsic electric field of the contact. It prevents the motion of electrons through the contact when a forward bias is applied across it. An increase in contact diameters from 5 to 700 μm results in decreasing the difference in forward and reverse saturation currents from five orders of magnitude to almost zero. The increase in the contact diameter, thus, results in decreasing periphery effect and absolute value of the built4n electric field. Adecrease in the barrier height( ≤0.6 V for D = 5 μm) also results in almost complete coincidence of forward and reverse saturation currents. At the reverse portions of the I–V characteristics, the effect of the built-in field manifests itself in a significant decrease in the effective height of the potential barrier due to a decrease in its width near the top and the substantial increase in the field electron emission through the barrier for lower energies. At the forward portions, it manifests itself in almost complete absence of the forward currents at low biases.     

Analysis of mechanisms for electron scattering in GaAs/AlxGa1−x As superlattices with doped quantum wells for longitudinal resonant current flow in high electric fields and at low temperatures

Formulas are derived for, and a numerical analysis made of, the dependence of the transverse phase relaxation time on electron energy for resonant current flow through GaAs/Al_xGa_1−x As superlattices with doped quantum wells. The parameters are chosen to be close to those of superlattices used for creating photodiodes for operation at λ⋍10 μm. The analysis is limited to the interactions of electrons with neutral atoms and impurity ions at low temperatures. Resonant current flow is ensured by an electric field that brings the ground state and the first excited state of the “Stark ladder” into resonance with neighboring, weakly interacting quantum wells. Fiz. Tekh. Poluprovodn. 33, 438–444 (April 1999)     

gEM Services Rooted in China - Expect to Harvest——Interview with CEO of gEM Services,Inc.,Mr. Richard Kulle

“At the beginning of any new entrepreneurship, you need to set one clear goal, which is a belief, a passion, and an eagerness to succeed, in order to lead your career toward a correct direction. During the process of starting a new business, there are many difficulties that need to be overcome;however, many difficulties can be overcome with such passion. Success means that you win in ALL aspects of the business, not only portions.“Richard Kulle     

Formation of local insulating regions in Si/Si—Ge structures by ion implantation with subsequent stain etching

It is suggested to use amorphous porous films obtained by stain etching for device isolation. The characteristics of the isolations, as applied to heteroepitaxial transistor structures, are compared with those obtained by trench isolation.