A simple model for quantum mechanical effects in hole inversionlayers in silicon PMOS devices

The effects of quantization of the inversion layer of MOSFET devices is an area of increasing importance as technology is aggressively scaled below 0.25 μm. Although electron inversion layers have attracted considerable interest, very little work has been reported for holes. This paper describes the implementation and results of a simple, computationally efficient model, appropriate for device simulators, for predicting the effects of hole inversion layer quantization. This model compares very favorably with experimental results and the predictions of a full-band, self-consistent Schrodinger-Poisson solver     

System requirements for Ka-band Earth-satellite propagation data

Accurate estimates of the propagation impairments that affect link quality and availability and determine signal interference fields are essential for the reliable design of telecommunication systems and the efficient use of the electromagnetic spectrum. Recent announcements by commercial entities of their intent to use Ka-band spectrum to supply satellite services have heightened interest in propagation data and models for these frequencies. This paper provides a brief overview of Ka-band Earth-satellite systems and requirements in relation to the need for specific types of propagation data     

Remote sensing of land surface temperature: the directional viewingeffect

Land surface temperature and emissivity products are currently being derived from satellite and aircraft remote sensing data using a variety of techniques to correct for atmospheric effects. Implicit in the commonly employed approaches is the assumption of isotropy in directional thermal infrared exitance. The authors' theoretical analyses indicate angular variations in apparent infrared temperature will typically yield land surface temperature errors ranging from 1 to 4°C unless corrective measures are applied     

A multichannel neural probe for selective chemical delivery at thecellular level

A bulk-micromachined multichannel silicon probe capable of selectively delivering chemicals at the cellular level as well as electrically recording from and stimulating neurons in vivo has been developed. The process buries multiple flow channels in the probe substrate, resulting in a hollow-core device, Microchannel formation requires only one mask in addition to those normally used for probe fabrication and is compatible with on-chip signal-processing circuitry. Flow in these microchannels has been studied theoretically and experimentally. For an effective channel diameter of 10 μm, a channel length of 4 mm, and water as the injected fluid, the flow velocity at 11 torr is about 1.3 mm/s, delivering 100 pl in 1 s. Intermixing of chemicals, with the tissue fluid due to natural diffusion through the outlet orifice becomes significant for dwell times in excess of about 30 min, and a shutter is proposed for chronic use. The probe has been used for acute monitoring of the neural responses to various chemical stimuli in guinea pig superior and inferior colliculus     

A thermal-fully hydrodynamic model for semiconductor devices andapplications to III-V HBT simulation

Because of the interaction between self-heating and hot carriers effects, neither isothermal nor conventional macrothermal models are adequate for the simulation of state-of-the-art power devices; instead, a detailed electro-thermal model accounting for nonstationary transport, such as the Thermal-Fully Hydrodynamic (T-FH) model, is required. We apply a one-dimensional (1-D) implementation of such a model to the simulation of AlGaAs/GaAs and InP/InGaAs Heterojunction Bipolar Transistors (HBTs), comparing the results with those provided by simplified models, and highlighting how deeply both nonlocal transport and self-heating affect the predicted device performance. The importance of the convective terms is assessed, and a new nonthermal mechanism for the output Negative Differential Resistance (NDR) is proposed     

Temperature performance of 1.3-/spl mu/m InGaAsP-InP lasers with different profile of p-doping

Temperature dependencies of the threshold current, device slope efficiency, and heterobarrier electron leakage current from the active region of InGaAsP-InP multiquantum-well (MQW) lasers with different profiles of acceptor doping were measured. We demonstrate that the temperature sensitivity of the device characteristics depends on the profile of p-doping, and that the variance in the temperature behavior of the threshold current and slope efficiency for lasers with different doping profiles cannot be explained by the change of the measured value of the leakage current with doping only. The entire experimental data can be qualitatively explained by suggesting that doping ran affect the value of electrostatic band profile deformation that affects temperature sensitivity of the output device characteristics. We show that doping of the p-cladding/SCH layer interface in InGaAsP-InP MQW lasers leads to improvement of the device temperature performance.     

A temperature-dependent model for the complex dielectric function of GaAs

In this work, we discuss a temperature-dependent model for the complex dielectric function for GaAs valid for the temperature range 31°C ≤ T ≤ 634°C. We describe our model, which is an extension of the critical point parabolic band method. This is a phenomenological method which is based on the physical processes occurring in the semiconductor, and has been previously demonstrated for composition-dependent models of the dielectric function for lattice-matched materials systems. We demonstrate the quality of the model in fitting optical data for individual temperatures, and compare our results to other established models. The data used for each fitting ranges from 1.25 to 4.5 eV. Using results obtained from the individual fits, we generate a temperature-dependent model that is valid for the range of temperatures given above. Also, we show how this model can be used to accurately determine the temperature (±2.3°C) of a material whose dielectric response has been obtained but was not included when generating the model.     

A Fourth Order Bandpass Delta-Sigma Modulator with Digitally Programmable Passband Frequency

The design and implementation of a fourth order switched-capacitorbandpass delta-sigma modulator with digitally programmable passbandis described. The quantization noise null can be programmed from0.4 (0.2f_s) to 0.6(0.3f_s) in steps of 0.01 (f_s/200)by changing digital switch settings. This design enables theA/D conversion of a bandpass signal with digital tuning of thecenter frequency for application in systems such as a transceiverIF stage. The modulator IC measures 4.8mm² in a2µ m CMOS process and achieves an SNR of 47 and59 dB over a 0.01 bandwidth at sampling ratesof 2.358 MHz and 1.25 MHz, respectively.     

Thickness dependence of stress-induced leakage currents in siliconoxide

The thickness dependence of high-voltage stress-induced leakage currents (SILC's) has been measured in oxides with thicknesses between 5 and 11 nm. The SILC's were shown to be composed of two components: a transient component and a DC component. Both components were due to trap-assisted tunneling processes. The transient component was caused by the tunnel charging and discharging of the stress-generated traps near the two interfaces. The DC component was caused by trap-assisted tunneling completely through the oxide. The thickness, voltage, and trap density dependences of both of these components were measured. The SILC's will affect data retention in electrically erasable programmable read-only memories (EEPROM's) and the DC component was used to estimate to fundamental limitations on oxide thicknesses     

Diversity performance of precoded orthogonal space-time block codes using limited feedback

Orthogonal space-time block codes (OSTBCs) are simple space-time codes that can be used for open-loop transmit diversity systems. OSTBCs, however, can only be designed for certain numbers of transmit antennas. Channel-dependent linear precoders have been proposed to overcome this deficiency, but it is not clear what conditions the precoder design must satisfy to guarantee full diversity order. In this letter, we show necessary and sufficient conditions for linear precoded OSTBCs to provide full diversity order. We show that limited feedback precoding can achieve full diversity order using fewer bits than limited feedback beamforming. We also present a simplified version of antenna subset selection for OSTBCs that can provide full diversity order with low complexity and only a small amount of feedback.