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Papers by Hamilton Carrillo-Nunez

2015 45th European Solid State Device Research Conference (ESSDERC), 2015

2015 International Workshop on Computational Electronics (IWCE), 2015

Innovative Devices, Architectures, and Applications, 2012

2013 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), 2013

The phonon-assisted band-to-band tunneling (BTBT) current has been computed for a cylindrical nan... more The phonon-assisted band-to-band tunneling (BTBT) current has been computed for a cylindrical nanowire tunneling field-effect transistor (TFET) with an all-round gate covering the source region. Although we have considered relatively thick wires, i.e. diameters ranging between 5 and 8 nm, we found that BTBT is considerably affected by the carrier confinement in the radial direction. Therefore, a self-consistent solution of the Schrödinger and Poisson equations must be carried out. For the latter, we have implemented a non-linear variational principle based on the modified local density approximation taking into account non-parabolic corrections for both conduction and valence bands. Our findings show not only that the confinement effects in nanowire TFETs have a stronger impact on the onset voltage of the tunneling current in comparison with their planar counterparts but also that the value of the onset voltage is overestimated when the valence band nonparabolicity is ignored.

Microelectronics Journal, 2008

In this work we analyze the localization of electronic states of low-dimensional systems. We choo... more In this work we analyze the localization of electronic states of low-dimensional systems. We choose a well known strictly onedimensional chain and an heuristic model for DNA-like molecules, in order to compare two established methods for analyzing the degree of localization, namely the localization length and participation ratio. r

Journal of Applied Physics, 2015

A rigorous framework to study direct band-to-band tunneling (BTBT) in homo-and hetero-junction se... more A rigorous framework to study direct band-to-band tunneling (BTBT) in homo-and hetero-junction semiconductor nanodevices is introduced. An interaction Hamiltonian coupling conduction and valence bands (CVBs) is derived using a multiband envelope method. A general form of the BTBT probability is then obtained from the linear response to the "CVBs interaction" that drives the system out of equilibrium.

2014 44th European Solid State Device Research Conference (ESSDERC), 2014

Extremely narrow and bulk-like p-type InAs-Si nanowire TFETs are studied using a full-band and at... more Extremely narrow and bulk-like p-type InAs-Si nanowire TFETs are studied using a full-band and atomistic quantum transport simulator based on the sp 3 d 5 s * tight-binding model and a drift-diffusion TCAD tool. As third option, the WKB approximation has been adapted to work in heterostructures through a careful choice of the imaginary dispersion. It is found that for ultra-scaled InAs-Si nanowire TFETs, the WKB approximation and the quantum transport results agree very well, suggesting that the former could be applied to larger hetero-TFET structures and considerably reduce the simulation time while keeping a high accuracy.

Journal of Applied Physics, 2014

Single dopant nanowire transistors can be viewed as the ultimate miniaturization of nano electron... more Single dopant nanowire transistors can be viewed as the ultimate miniaturization of nano electronic devices. In this work we theoretically investigate the influence of the electron-phonon coupling on their transport properties using a non equilibrium Greens function approach in the selfconsistent Born approximation. For an impurity located at the center of the wire we find that, at room temperature, acoustic phonons broaden the impurity level so that the bistability predicted in the ballistic regime is suppressed. Optical phonons are found to have a beneficial impact on carrier transport via a phonon-assisted tunneling effect. We discuss the position and temperature dependence of these effects, showing that such systems might be very promising for engineering of ultimate devices. * carrillh@iis.ee.ethz.ch; Current address: Integrated Systems laboratory ETH Zürich,

Solid-State Electronics, 2013

The Zener tunneling current flowing through a biased, abrupt p-n junction embedded in a cylindric... more The Zener tunneling current flowing through a biased, abrupt p-n junction embedded in a cylindrical silicon nanowire is calculated. As the band gap becomes indirect for sufficiently thick wires, Zener tunneling and its related transitions between the valence and conduction bands are mediated by short-wavelength phonons interacting with mobile electrons. Therefore, not only the high electric field governing the electrons in the space-charge region but also the transverse acoustic (TA) and transverse optical (TO) phonons have to be incorporated in the expression for the tunneling current. The latter is also affected by carrier confinement in the radial direction and therefore we have solved the Schrödinger and Poisson equations self-consistently within the effective mass approximation for both conduction and valence band electrons. We predict that the tunneling current exhibits a pronounced dependence on the wire radius, particularly in the high-bias regime.

Physical Review B, 2008

In this work we discuss and compare different definitions for localization of electronic states i... more In this work we discuss and compare different definitions for localization of electronic states in lowdimensional systems. We choose a heuristic model for DNA-like molecules as a system prototype in order to establish ranges of equivalence for the localization length obtained from both the conductance and participation ratios. The results suggest also criteria to infer the extension of wave function in mesoscopic systems within the diffusive transport regime as complementary information to the localization length.

We analyze the density of states of neutral donors randomly distributed inside a In(Ga)As selfass... more We analyze the density of states of neutral donors randomly distributed inside a In(Ga)As selfassemled quantum dot. The curves of the dependencies of donor's ground state binding energies on the distance to the axis of the disk-like, lens-like, pyramid-like and ring-like geometry are calculated. It is shown that the Van-Hove singularity presemted in these curves provides pronounced peaks in the density impurity states. It is found that the curves of the impurity states have structured shapes with some separated peaks in the high-energy part of the spectrum. Se analiza la densidad de estados de donadoras neutras distribuidas aleatoriamente dentro un punto cuántico autoensamblado de In(Ga)As. Las curvas de dependencia de energías de enlace del estado base de las donadoras, en función de la distancia hasta el eje de los puntos cuánticos con las geometrías similares a un disco, lente, pirámide y anillo se han calculadas. Se muestra que las singularidades de Van-Hove presentadas en e...

Journal of Applied Physics, 2010

A simplified quantum mechanical model is developed to investigate quantum transport features such... more A simplified quantum mechanical model is developed to investigate quantum transport features such as the electron concentration and the current flowing through a silicon nanowire metal-oxide-semiconductor field-effect transistor ͑MOSFET͒. In particular, the electron concentration is extracted from a self-consistent solution of the Schrödinger and Poisson equations as well as the ballistic Boltzmann equation which have been solved by exploiting a nonlinear variational principle within the framework of the generalized local density approximation. A suitable action functional has been minimized and details of the implementation and its numerical minimization are given. The current density and its related current-voltage characteristics are calculated from the one-dimensional ballistic steady-state Boltzmann transport equation which is solved analytically by using the method of characteristic curves. The straightforward implementation, the computational speed and the good qualitative behavior of the transport characteristics observed in our approach make it a promising simulation method for modeling quantum transport in nanowire MOSFETs.