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Learning-Related Values in Young Children’s Storybooks: An Investigation in the United States, China, and Mexico
This research examined the prevalence of learning-related values in children’s storybooks in the United States, China, and Mexico. Storybooks ( N = 157) were randomly selected from government-recommended booklists in each country. Trained coders assessed the prevalence of learning-related beliefs (e.g., malleability of ability), motivated cognitions (e.g., achievement orientation), and behaviors (e.g., effort) in the storybooks. A set of MANOVAs revealed that Chinese (vs. American and Mexican) storybooks contained more instances of learning-related beliefs and behaviors. For example, Chinese storybooks included more instances of achievement-related goals and behaviors, relative to storybooks in the United States and Mexico. With the exception of achievement goals and helplessness, the prevalence of learning-related qualities was largely similar in the United States and Mexico
Environmental sensitivity of n-i-n and undoped single GaN nanowire photodetectors
In this work, we compare the photodetector performance of single defect-free
undoped and n-in GaN nanowires (NWs). In vacuum, undoped NWs present a
responsivity increment, nonlinearities and persistent photoconductivity effects
(~ 100 s). Their unpinned Fermi level at the m-plane NW sidewalls enhances the
surface states role in the photodetection dynamics. Air adsorbed oxygen
accelerates the carrier dynamics at the price of reducing the photoresponse. In
contrast, in n-i-n NWs, the Fermi level pinning at the contact regions limits
the photoinduced sweep of the surface band bending, and hence reduces the
environment sensitivity and prevents persistent effects even in vacuum
Intersubband transitions in nonpolar GaN/Al(Ga)N heterostructures in the short and mid-wavelength infrared regions
This paper assesses nonpolar m- and a-plane GaN/Al(Ga)N multi-quantum-wells
grown on bulk GaN for intersubband optoelectronics in the short- and
mid-wavelength infrared ranges. The characterization results are compared to
those for reference samples grown on the polar c-plane, and are verified by
self-consistent Schr\"odinger-Poisson calculations. The best results in terms
of mosaicity, surface roughness, photoluminescence linewidth and intensity, as
well as intersubband absorption are obtained from m-plane structures, which
display room-temperature intersubband absorption in the range from 1.5 to 2.9
um. Based on these results, a series of m-plane GaN/AlGaN multi-quantum-wells
were designed to determine the accessible spectral range in the mid-infrared.
These samples exhibit tunable room-temperature intersubband absorption from 4.0
to 5.8 um, the long-wavelength limit being set by the absorption associated
with the second order of the Reststrahlen band in the GaN substrates
High In-content InGaN layers synthesized by plasma-assisted molecular-beam epitaxy: growth conditions, strain relaxation and In incorporation kinetics
We report the interplay between In incorporation and strain relaxation
kinetics in high-In-content InxGa1-xN (x = 0.3) layers grown by plasma-assisted
molecular-beam epitaxy. For In mole fractions x = 0.13-0.48, best structural
and morphological quality is obtained under In excess conditions, at In
accumulation limit, and at a growth temperature where InGaN decomposition is
active. Under such conditions, in situ and ex situ analysis of the evolution of
the crystalline structure with the growth thickness points to an onset of
misfit relaxation after the growth of 40 nm, and a gradual relaxation during
more than 200 nm which results in an inhomogeneous strain distribution along
the growth axis. This process is associated with a compositional pulling
effect, i.e. indium incorporation is partially inhibited in presence of
compressive strain, resulting in a compositional gradient with increasing In
mole fraction towards the surface
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