The effect of uncertainty on learning in game-like environments

Cataloged from PDF version of article.Considering the role of games for educational purposes, there has an increase in interest among educators in applying strategies used in popular games to create more engaging learning environments. Learning is more fun and appealing in digital educational games and, as a result, it may become more effective. However, few research studies have been conducted to establish principles based on empirical research for designing engaging and entertaining games so as to improve learning. One of the essential characteristics of games that has been unexplored in the literature is the concept of uncertainty. This study examines the effect of uncertainty on learning outcomes. In order to better understand this effect on learning, a game-like learning tool was developed to teach a database concept in higher education programs of software engineering. The tool is designed in two versions: one including uncertainty and the other including no uncertainty. The experimental results of this study reveal that uncertainty enhances learning. Uncertainty is found to be positively associated with motivation. As motivation increases, participants tend to spend more time on answering the questions and to have higher accuracy in these questions

Structural and electrical characterizations of InxGa1-xAs/InP structures for infrared photodetector applications

Cataloged from PDF version of article.Three InGaAs/InP structures for photodetector applications were grown with different indium compositions by MBE technique. The structural properties of the samples have been obtained by means of high resolution X-ray diffraction and secondary ion mass spectrometry measurements. Three InGaAs/InP metal-semiconductor-metal devices were fabricated at room temperature. The experimental forward and reverse bias current-voltage characteristics of the devices such as ideality factor, barrier height, and saturation current were evaluated considering the structural properties of the grown structures. The carrier recombination lifetime and diffusion length in the devices were also calculated using carrier density and mobility data obtained with Hall effect measurement at room temperature. It was determined that all room temperature fabricated devices improved the Schottky barrier height. Especially, the device fabricated on the lower mismatched structure exhibited barrier height enhancement from 0.2 eV, which is the conventional barrier height to 0.642 eV. In addition, the obtained results show that the room temperature fabricated devices on InGaAs/InP structures can be convenient for infrared photodetector applications. (C) 2014 AIP Publishing LLC

The effect of Si(x)N(y) interlayer on the quality of GaN epitaxial layers grown on Si(111) substrates by MOCVD

Cataloged from PDF version of article.In the present paper, the effects of nitridation on the quality of GaN epitaxial films grown on Si(111) substrates by metal-organic chemical vapor phase deposition (MOCVD) are discussed. A series of GaN layers were grown on Si(111) under various conditions and characterized by Nomarski microscopy (NM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD), and room temperature (RT) photoluminescence (PL) measurements. Firstly, we optimized LT-AlN/HT-AlN/Si(111) templates and graded AlGaN intermediate layers thicknesses. In order to prevent stress relaxation, step-graded AlGaN layers were introduced along with a crack-free GaN layer of thickness exceeding 2.2 mu m. Secondly, the effect of in situ substrate nitridation and the insertion of an Si(x)N(y) intermediate layer on the GaN crystalline quality was investigated. Our measurements show that the nitridation position greatly influences the surface morphology and PL and XRD spectra of GaN grown atop the Si(x)N(y) layer. The X-ray diffraction and PL measurements results confirmed that the single-crystalline wurtzite GaN was successfully grown in samples A (without Si(x)N(y) layer) and B (with Si(x)N(y) layer on Si(111)). The resulting GaN film surfaces were flat, mirror-like, and crack-free. The full-width-at-half maximum (FWHM) of the X-ray rocking curve for (0002) diffraction from the GaN epilayer of the sample B in omega-scan was 492 arcsec. The PL spectrum at room temperature showed that the GaN epilayer had a light emission at a wavelength of 365 nm with a FWHM of 6.6 nm (33.2 meV). In sample B, the insertion of a Si(x)N(y) intermediate layer significantly improved the optical and structural properties. In sample C (with Si(x)N(y) layer on Al(0.11)Ga(0.89)N interlayer). The in situ depositing of the, however, we did not obtain any improvements in the optical or structural properties. (C) 2008 Elsevier B.V. All rights reserved

The effect of competition on learning in games

Today serious games are having an important impact on areas other than entertainment. Studies show that serious games have a potential of creating learning environments to better reach the educational and training goals. The game design characteristics and game elements are need to be explored in detail for increasing the expected benefits of the gaming environments. In this study, the effect of competition, one of the design elements of game environments, on learning is analyzed experimentally. The study is conducted with 142 students. The results of this study show that when a competition environment is created in a serious game, motivation and post-test scores of learners improve significantly. The results of this study are expected to guide the serious game designers for improving the potential benefits of serious games. © 2015 Elsevier Ltd

On the profile of frequency and voltage dependent interface states and series resistance in (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures by using current–voltage (I–V) and admittance spectroscopy methods

Cataloged from PDF version of article.In order to explain the experimental effect of interface states (N-ss) and series resistance (R-s) of device on the non-ideal electrical characteristics, current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/omega-V) characteristics of (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures were investigated at room temperature. Admittance measurements (C-V and G/omega-V) were carried out in frequency and bias voltage ranges of 2 kHz-2 MHz and (-5 V)-(+5 V), respectively. The voltage dependent R-s profile was determined from the I-V data. The increasing capacitance behavior with the decreasing frequency at low frequencies is a proof of the presence of interface states at metal/semiconductor (M/S) interface. At various bias voltages, the ac electrical conductivity (sigma(ac)) is independent from frequencies up to 100 kHz, and above this frequency value it increases with the increasing frequency for each bias voltage. In addition, the high-frequency capacitance (C-m) and conductance (G(m)/omega) values measured under forward and reverse bias were corrected to minimize the effects of series resistance. The results indicate that the interfacial polarization can more easily occur at low frequencies. The distribution of N-ss and R-s is confirmed to have significant effect on non-ideal I-V. C-V and G/omega-V characteristics of (Ni/Au)/Al0.22Ga038N/AlN/GaN heterostructures. (C) 2011 Elsevier Ltd. All rights reserved

Strain analysis of the GaN epitaxial layers grown on nitridated Si(111) substrate by metal organic chemical vapor deposition

Cataloged from PDF version of article.The strain analysis of GaN film on nitridated Si(111) substrate with different growth times between 0 and 660 s via metal organic chemical vapor deposition (MOCVD) was conducted based on the precise measurement of the lattice parameters by using high-resolution X-ray diffraction (HR-XRD). The nitridation time (NT) was changed at a fixed growth condition. The a- and c-lattice parameters were measured, followed by the in-plane and out-of-plane strains. Then, the biaxial and hydrostatic components were extracted from the total strain values obtained, and were then discussed in the present study as functions of the NT. The biaxial strain and stress are also strongly affected by the non-uniformity of the SiNx buffer layer thickness. Published by Elsevier Ltd

A study of semi-insulating GaN grown on AlN buffer/sapphire substrate by metalorganic chemical vapor deposition

Cataloged from PDF version of article.We report the remarkably improved crystal quality of semi-insulating GaN grown by metalorganic chemical vapor deposition on an AlN buffer layer, which is deposited on sapphire substrate. The electrical and structural properties are characterized by dark current-voltage transmission line model and X-ray diffraction measurements. It is found that the crystal quality of the GaN epilayer is strongly related with the growth temperature of the decreased-temperature GaN interlayer. In comparison with the normal GaN grown on sapphire, the crystal quality is remarkably improved along with a semi-insulating electrical character. The high-mobility field effect transistors device based on the semi-insulating GaN shows good pinch off properties. Our electrical measurement results of GaN grown directly on an AlN buffer indicated that the as-grown-undoped GaN is naturally semi-insulating material. The origination of the residual donors in normal GaN grown on sapphire substrate is also discussed. (c) 2006 Elsevier B.V. All rights reserved

The profile of temperature and voltage dependent series resistance and the interface states in (Ni/Au)/Al0.3Ga0.7N/AlN/GaN heterostructures

Cataloged from PDF version of article.The profile of the interface state densities (N(ss)) and series resistances (R(s)) effect on capacitance-voltage (C-V) and conductance-voltage (G/omega-V) of (Ni/Au)/Al(x)Ga(1-x)N/AlN/GaN heterostructures as a function of the temperature have been investigated at 1 MHz. The admittance method allows us to obtain the parameters characterizing the metal/semiconductor interface phenomena as well as the bulk phenomena. The method revealed that the density of interface states decreases with increasing temperature. Such a behavior of N(ss) can be attributed to reordering and restructure of surface charges. The value of series R(s) decreases with decreasing temperature. This behavior of R(s) is in obvious disagreement with that reported in the literature. It is found that the N(ss) and R(s) of the structure are important parameters that strongly influence the electrical parameters of (Ni/Au)/Al(x)Ga(1-x)N/AlN/GaN(x = 0.22) heterostructures. In addition, in the forward bias region a negative contribution to the capacitance C has been observed, that decreases with the increasing temperature. Copyright (C) 2010 John Wiley & Sons, Ltd

On the profile of frequency dependent dielectric properties of (Ni/Au)/GaN/Al0.3Ga0.7N heterostructures

Cataloged from PDF version of article.The voltage (V) and frequency (f) dependence of dielectric characteristics such as dielectric constant (epsilon'), dielectric loss (epsilon ''), dielectric loss tangent (tan (5) and real and imaginary part of electrical modulus (M' and M '') of the (Ni/Au)/GaN/Al0.3Ga0.7N heterostructures have been investigated by using experimental admittance spectroscopy (capacitance-voltage (C-V) and conductance-voltage (G/w-V)) measurements at room temperature. Experimental results show that the values of the epsilon', epsilon '', tan delta and the real and imaginary parts of the electric modulus (M' and M '') obtained from the C and G/w measurements were found to be strong function of frequency and applied bias voltage especially in depletion region at low frequencies. These changes in dielectric parameters can be attributed to the interfacial GaN cap layer, interface polarization and a continuous density distribution of interface states and their relaxation time at metal/semiconductor interface. While the values of the epsilon' decrease with increasing frequencies, tan delta, M' and M '' increase with the increasing frequency. Also, the dielectric loss (epsilon '') have a local maximum at about frequency of 100 kHz. It can be concluded that the interface polarization can occur more easily at low frequencies with the number of interface states located at the metal/semiconductor interface. (C) 2010 Elsevier Ltd. All rights reserved

The persistent photoconductivity effect in AIGaN/GaN heterostructures grown on sapphire and SiC substrates

Cataloged from PDF version of article.In the present study, we reported the results of the investigation of electrical and optical measurements in Al(x)Ga(1-x)N/GaN heterostructures (x=0.20) that were grown by way of metal-organic chemical vapor deposition on sapphire and SiC substrates with the same buffer structures and similar conditions. We investigated the substrate material effects on the electrical and optical properties of Al(0.20)Ga(0.80)N/GaN heterostructures. The related electrical and optical properties of Al(x)Ga(1-x)N/GaN heterostructures were investigated by variable-temperature Hall effect measurements, photoluminescence (PL), photocurrent, and persistent photoconductivity (PPC) that in turn illuminated the samples with a blue (lambda=470 nm) light-emitting diode (LED) and thereby induced a persistent increase in the carrier density and two-dimensional electron gas (2DEG) electron mobility. In sample A (Al(0.20)Ga(0.80)N/GaN/sapphire), the carrier density increased from 7.59x10(12) to 9.9x10(12) cm(-2) via illumination at 30 K. On the other hand, in sample B (Al(0.20)Ga(0.80)N/GaN/SiC), the increments in the carrier density were larger than those in sample A, in which it increased from 7.62x10(12) to 1.23x10(13) cm(-2) at the same temperature. The 2DEG mobility increased from 1.22x10(4) to 1.37x10(4) cm(-2)/V s for samples A and B, in which 2DEG mobility increments occurred from 3.83x10(3) to 5.47x10(3) cm(-2)/V s at 30 K. The PL results show that the samples possessed a strong near-band-edge exciton luminescence line at around 3.44 and 3.43 eV for samples A and B, respectively. The samples showed a broad yellow band spreading from 1.80 to 2.60 eV with a peak maximum at 2.25 eV with a ratio of a near-band-edge excitation peak intensity up to a deep-level emission peak intensity ratio that were equal to 3 and 1.8 for samples A and B, respectively. Both of the samples that were illuminated with three different energy photon PPC decay behaviors can be well described by a stretched-exponential function and relaxation time constant tau as well as a decay exponent beta that changes with the substrate type. The energy barrier for the capture of electrons in the 2DEG channel via the deep-level impurities (DX-like centers) in AlGaN for the Al(0.20)Ga(0.80)N/GaN/sapphire and Al(0.20)Ga(0.80)N/GaN/SiC heterojunction samples are 343 and 228 meV, respectively. The activation energy for the thermal capture of an electron by the defects Delta E changed with the substrate materials. Our results show that the substrate material strongly affects the electrical and optical properties of Al(0.20)Ga(0.80)N/GaN heterostructures. These results can be explained with the differing degrees of the lattice mismatch between the grown layers and substrates. (C) 2008 American Institute of Physics