IEEE transactions on very large scale integration (VLSI) systems

Semiconductor nanowires have attracted extensive interest as one of the best-defined classes of nanoscale building blocks for the bottom-up assembly of functional electronic and optoelectronic devices over the past two decades. The article provides a comprehensive review of the continuing efforts in exploring semiconductor nanowires for the assembly of functional nanoscale electronics and macroelectronics. Specifically, we start with a brief overview of the synthetic control of various semiconductor nanowires and nanowire heterostructures with precisely controlled physical dimension, chemical composition, heterostructure interface, and electronic properties to define the material foundation for nanowire electronics. We then summarize a series of assembly strategies developed for creating well-ordered nanowire arrays with controlled spatial position, orientation, and density, which are essential for constructing increasingly complex electronic devices and circuits from synthetic semiconductor nanowires. Next, we review the fundamental electronic properties and various single nanowire transistor concepts. Combining the designable electronic properties and controllable assembly approaches, we then discuss a series of nanoscale devices and integrated circuits assembled from nanowire building blocks, as well as a unique design of solution-processable nanowire thin-film transistors for high-performance large-area flexible electronics. Last, we conclude with a brief perspective on the standing challenges and future opportunities.

Nanowire Electronics: From Nanoscale to Macroscale

INTERSUBBAND RELAXATION IN GaAs/Al x Ga 1-x As QUANTUM WELL STRUCTURES

Two concentration ranges of silicon doping in MBE-grown GaAs films have been investigated in some detail. In lightly doped films, with a free-electron concentration of ≈1016cm−3, low-temperature photoluminescence spectra have been analysed to develop a model to account for spectral features previously attributed to Ge and Si acceptor levels. In heavily doped films, a maximum free-electron concentration of ≈7×1018 cm−3 has been obtained, which is only rather weakly dependent on growth conditions and the nature of the arsenic species (As2 or As4). Transmission electron microscopy has shown that no significant precipitation effects occur when higher Si fluxes are used but there is evidence for autocompensation. The maximum PL intensity (300 K) is found at a lower free electron concentration then with Sn-doped films, and is more sharply peaked, but there is no evidence for an anomalous Moss-Burstein shift.

Silicon doping of MBE-grown GaAs films

Physics of Semiconductor Devices. S. M. Sze. Interscience (Wiley), New York, 1969. xvi + 814 pp., illus. $19.95

In this paper, a technique for implementing low-power Dual Edge Triggered Flip Flop (DETFF) is introduced. Dual edge triggered flip flops has many advantages in low power VLSI compared to SETFF. The Proposed low power DETFF is implemented and compared with conventional DETFF at same simulation conditions. CAD tool based simulation and comparison between the non-conventional DET flip-flop with the conventional DETFF shows that the proposed DETFF reduces power dissipation by 66% reducing the no. of transistors used while keeping the same data rate.

Design and implementation of low power dual edge triggered flip-flop using GDI and TG for high speed FIR filter

Design of a low power, double throughput cyclic combinational gate diffusion input based radix-4 MBW multiplier and accumulator unit for on-chip RISC processors of MEMS sensor

The mobility of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures changes significantly with Al content in the AlGaN layer and also determined from temperature-dependent Hall Effect measurements, while few mechanism analysis focus on it. Theoretical calculation and analysis of the 2DEG mobility in AlGaN/GaN heterostructures are carried out based on the recently reported experimental data. We have considered different scattering mechanism while calculating electron mobility, such as, polar optical phonon scattering, ionized impurity scattering, background impurity scattering. The result is that at low temperatures ion impurity scattering is the dominant scattering mechanism and at high temperatures polar optical phonon scattering is dominant. The variation of conductivity, drain current and power dissipation with temperature in AlGaN/GaN has been studied considering phonon interactions with electrons. The conductivity and power dissipation in AlGaN/GaN is highest at 80 Ks phonons.

Effects of scattering on transport properties in GaN

Analysis of electron transport in AlGaN/GaN superlattice HEMTs for isotopes 14 N and 15 N

The presence of discrete breathers (DBs) has already been described in nonlinear photonic materials, such as ferroelectrics and metamaterials (MMs) by the Klein?Gordon (K?G) approach. Rectification of energy transport in MMs in the presence of an appropriate external field is studied via symmetry breaking leading to directed energy transport or ratchet behaviour. Based on the earlier development of the K?G equation in a MM system with a split-ring resonator for antenna applications, a theoretical model for current density is worked out by symmetry analysis and its violation to characterize the ratchet effect. The time-averaged current shows interesting results against phase shift in the ac driver. These data are further related to various parameters, such as coupling and damping in the system. For MMs, this opens a new application for rectification using ratchets.

Aniruddha Ghosal

Papers

Design and implementation of low power dual edge triggered flip-flop using GDI and TG for high speed FIR filter

Design of a low power, double throughput cyclic combinational gate diffusion input based radix-4 MBW multiplier and accumulator unit for on-chip RISC processors of MEMS sensor

Effects of scattering on transport properties in GaN

Analysis of electron transport in AlGaN/GaN superlattice HEMTs for isotopes 14 N and 15 N

Rectification of energy transport in nonlinear metamaterials via ratchets