Photoluminescence Spectra of Gallium Arsenide Nanowire and Confinement Effect
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Date
2011-06
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Addis Ababa University
Abstract
In this paper we present a detailed analysis of the atomic,optical and electronic structures of GaAs
nanowires grown along [111]. and we reveal interesting trends among variation gap and size
,oscillator strength and size ,quantum confinement and size of particle and and the overall
photoluminescence of GaAs nanowire and observing their spectra by varying diameters.
The size (d) dependence of photoluminescence from nanocrystalline GaAs nanowire semiconductors
is examined. The overall luminescence is determined by two distinct physical mechanisms:
1) the variation of the semiconductor gap with size d (typically ~1/ d , 1 and
2) the variation of the oscillator strength f osc with size t͑ ypically 1/ d , 5≤≤6 We present
an analytical framework to understand the luminescence line shape based on the above two
mechanisms, taking no recourse to computational simulations. We show that the peak energy
varies with the mean particle size d0 as d0 − , where is an effective exponent
determined by the disorder in the system.
Semiconductor nanowires have occupied the center of scientific interest because of their unique
electronic nature. Among the group III-V compound , the gallium arsenide nanowire have been the
focus of this research due to their importance in constructing fast microelectric devices. The electronic
structures of gallium arsenide nanowire were studied.
Our work shows that the presence of disorder can shift the photoluminescence peak position.In the
absence of a strong size dependence of the oscillator strength ,the peak is redshifted. This allows one to
assume reasonable values for the excitonic energy (~50 meV) . However,if the oscillator strength is
strongly dependent on size,the peak blue shift so large excitonic energies are needed to explain the
disparity.
Attempts to understand the experimental data on the basis of calculation,and curve fitting model are the
core method of this thesis.
However, the surface states associated with the surface atoms having two dangling bonds in zincblende
stacking occur in the band gap and can decrease the band gap to change the nanowire from
semiconducting to metallic state. These nanowires become semiconducting upon hydrogen passivation.
Even if the band gap of some nanowires decreases with increasing diameter and hence reveals the
quantum confinement effect, generally the band-gap variation is rather complex, and depends on the
type and geometry, diameter, type of relaxation, and also whether the dangling bonds of surface atoms
are saturated with hydrogen
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Keywords
Nanowire and Confinement Effect