Semiconductor Nanostructures towards Electronic and Optoelectronic Device Applications (original) (raw)

Low Dimensional Semiconductor Structures

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Defects in semiconductor nanostructures

Pramana, 2008

Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow impurities in semiconductors. Although work in semiconductor nanostructures (SN) has been in progress for the past two decades, the role of impurities in them has been only sketchily studied. We outline theoretical approaches to the electronic structure of shallow impurities in SN and discuss their limitations. We find that shallow levels undergo a SHADES (SHAllow-DEep-Shallow) transition as the SN size is decreased. This occurs because of the combined effect of quantum confinement and reduced dielectric constant in SN. Level splitting is pronounced and this can perhaps be probed by ESR and ENDOR techniques. Finally, we suggest that a perusal of literature on (semiconductor) cluster calculations carried out 30 years ago would be useful.

Size Effects on Semiconductor Nanoparticles

Nanoparticles, 2014

This chapter addresses the fundamental concepts needed to understand the impact of size reduction on the electronic structure and optoelectronic properties of semiconductor nanostructures, with emphasis on quantum confinement effects. This effect is explained by two different approaches: the "top-down" and the "bottom-up". Subsequently, a brief description of the optical properties of semiconductor nanocrystals is presented. This is followed by sections discussing the essential characteristics of nanocrystals consisting of two (or more) different semiconductors joined together by heterointerfaces (i.e., heteronanocrystals). Moreover, the essential differences between the impact of size reduction on semiconductors in comparison to metals and insulators is discussed. The chapter ends by briefly discussing the potential applications of semiconductor nanoparticles.

Semiconductor Nanocrystals: Structure, Properties, and Band Gap Engineering

Accounts of Chemical Research, 2010

S emiconductor nanocrystals are tiny light-emitting particles on the nanometer scale. Researchers have studied these particles intensely and have developed them for broad applications in solar energy conversion, optoelectronic devices, molecular and cellular imaging, and ultrasensitive detection. A major feature of semiconductor nanocrystals is the quantum confinement effect, which leads to spatial enclosure of the electronic charge carriers within the nanocrystal. Because of this effect, researchers can use the size and shape of these "artificial atoms" to widely and precisely tune the energy of discrete electronic energy states and optical transitions. As a result, researchers can tune the light emission from these particles throughout the ultraviolet, visible, near-infrared, and mid-infrared spectral ranges. These particles also span the transition between small molecules and bulk crystals, instilling novel optical properties such as carrier multiplication, single-particle blinking, and spectral diffusion. In addition, semiconductor nanocrystals provide a versatile building block for developing complex nanostructures such as superlattices and multimodal agents for molecular imaging and targeted therapy. In this Account, we discuss recent advances in the understanding of the atomic structure and optical properties of semiconductor nanocrystals. We also discuss new strategies for band gap and electronic wave function engineering to control the location of charge carriers. New methodologies such as alloying, doping, strain-tuning, and band-edge warping will likely play key roles in the further development of these particles for optoelectronic and biomedical applications.

Advancement of Group IV Nanostructures Nanophotonics and Nanoelectronics

2014

Si quantum dots for future electronics and photonics Shunri Oda Quantum Nanoelectronics Research Center, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Quantum dot structures, where electrons are confined three-dimensionally in the sub-10 nm scale, show characteristics quite different from conventional bulk structures. Recent progress in the fabrication technology of silicon nanostructures has made possible observations of novel electrical and optical properties of silicon quantum dots, such as single electron tunneling, ballistic transport, visible photo-luminescence and high-efficiency electron emission. Silicon quantum dots are fabricated either by bottom-up or top-down processes. Fabrication and electrical/opto-electrical characterization of nanocrystalline Si films by plasma processes and coupled Si quantum dots by electron beam lithography processes are discussed. Si nanocrystals in SiO2 for spectral shaping in future photovoltaics T. Gregorkiewicz Van der Waals –...

Production and Characterization of Quantum Nanostructures of Epitaxial Semiconductors

Le Journal de Physique IV, 1995

An experimental study has been performed using RBS and AFM characterization on InP islands grown by MOVPE on GaAs substrate, aiming to understand the influence of the growth parameters on the size distribution of the nanostructures. In the temperature range 580 +650 O C the total amount of deposited InP is independent of temperature which, on the contrary, affects the morphology of the growing islands.This work is part of a broader investigation on the feasibility of self organized growth to obtain nanosized semiconductor islands (Quantum Dots) by exploiting the mismatch-induced strain between substrate and epilayer in MOVPE deposition. In particular our data on the islands size are in very good agreement with preliminary indications of analytical and numerical models on the minimization of the total energy of the island-substrate system.