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Strained InGaAs/GaAs quantum wells were grown on (111) B GaAs substrates and the pyroelectric coefficient was determined.

We report the comprehensive study on the temperature dependence of excitonic properties for an InGaAs/GaAs p-i-n multiquantum well structure grown on a (111)B GaAs substrate by molecular-beam epitaxy using photoreflectance spectroscopy, in which the pyroelectric effect (temperature dependence of piezoelectric field) is taken into account. The temperature dependence of the confined transition energies was investigated in terms of a Varshni’s semiempirical equation and a Bose–Einstein expression to analyze the excitonic properties. We also determined the optical-phonon energy and strength of electron-phonon coupling for the <111> crystallographic directions of this material system, as well as the interface roughness from an analysis of the temperature dependence of PR broadening parameters. [ABSTRACT FROM AUTHOR]

We investigate the effect of the properties of an intracavity diamond heat spreader on the lasing performance of vertical-external-cavity surface-emitting lasers. We compared two intracavity diamonds with different average birefringences. When a polarization selective element is inserted into the cavity, the infrared output powers are reduced by 13% and 7%, respectively, for the samples with higher and lower average birefringences. The pump-power limited maximum green output powers were changed from 3 to 5.2 W by rotating the samples with lower average birefringence. In order to explain the variation in green output power, the additional round-trip loss caused by diamond birefringence was analyzed theoretically and experimentally. We found that the loss can be reduced when axes of the birefringence are aligned to the axes of the polarization selective element. [ABSTRACT FROM AUTHOR]

We report on the demonstration of highly efficient blue lasers based on intracavity frequency doubling vertical-external-cavity surface-emitting lasers (VECSELs). By optimizing the number of InGaAs quantum wells and employing Al0.3Ga0.7As carrier blocking layers in resonant periodic gain structures, we observed the pump-power-limited output power of 4.5 W at 920 nm for an InGaAs/GaAs quantum well VECSEL. With a frequency doubling LiB3O5 crystal inside the cavity, 1.9 W continuous-wave 460 nm blue output was demonstrated. Power conversion efficiencies (=output power/pump input power) of 22.5% and 9.5% are realized for λ∼920 nm and λ∼460 nm, respectively. [ABSTRACT FROM AUTHOR]

In this work we employed photoreflectance spectroscopy over the temperature range 11-300 K to investigate the heterointerfaces of a strained piezoelectric InGaAs/GaAs single quantum well structure grown on a (111)A GaAs substrate by metalorganic vapor phase epitaxy. Photoreflectance spectroscopy measurements in combination with a theoretical analysis using the quantum well structural parameters obtained by high-resolution x-ray diffractometry enabled us to evaluate separately the abruptness and roughness of the quantum well interfaces. The excellent agreement between the experimental and calculated transition energies for a quantum well structure with a well width of 41 Å and 13% In demonstrates that the heterointerfaces are abrupt. From a theoretical analysis of the temperature dependence of the photoreflectance broadening parameters, based on the Bose-Einstein phonon-coupling model, we determined the longitudinal optical phonon energy and the electron-phonon coupling strength. This analysis shows an interface roughness of less than ±1 monolayer. These results in conjunction with the observation of a narrow photoluminescence linewidth of 9.1 meV indicate the achievement of essentially atomically smooth interfaces in a highly strained (∼1%) piezoelectric InGaAs/GaAs quantum well structure. [ABSTRACT FROM AUTHOR]

In this work we used the differential photocurrent technique to measure the strain-induced piezoelectric field in pseudomorphic In[sub x]Ga[sub 1-x]As/GaAs heterostructures grown by molecular beam epitaxy on (111)B GaAs substrates. Single and multiple quantum well p-i-n diodes with two different In fractions in the well were analyzed in the temperature range of 25-300 K. Our results for a sample with a 17% In fraction confirm the previously reported value of the pyroelectric coefficient for a similar sample obtained by photoreflectance spectroscopy, hence, the equivalence of the differential photocurrent and photoreflectance techniques is also demonstrated. For a sample with 21% In, we report experimental determination of the temperature dependence of the piezoelectric constant and, therefore, of the strain-induced component of the pyroelectric coefficient. [ABSTRACT FROM AUTHOR]

We report that the charged oxygen vacancies are the key element to induce a resistive switching in copper oxide resistive devices and an external bias drifts the charged vacancies at the metal/oxide Schottky interface causing the switching phenomenon by in situ transmission electron microscopy. Notable results are that the switching polarity is determined by the charge of the vacancies and that the voltage inducing non-volatile switching behavior originates from the Schottky barrier at the interface, which clarifies the origin of resistive switching and provides a design strategy for oxide resistive devices. [ABSTRACT FROM AUTHOR]

The interfacial electronic structures of a bilayer of fullerene (C60) and zinc phthalocyanine (ZnPc) grown on vanadium pentoxide (V2O5) thin films deposited using radio frequency sputtering under various conditions were studied using X-ray and ultraviolet photoelectron spectroscopy. The energy difference between the highest occupied molecular orbital (HOMO) level of the ZnPc layer and the lowest unoccupied molecular orbital (LUMO) level of the C60 layer was determined and compared with that grown on an indium tin oxide (ITO) substrate. The energy difference of a heterojunction on all V2O5 was found to be 1.3~1.4 eV, while that on ITO was 1.1 eV. This difference could be due to the higher binding energy of the HOMO of ZnPc on V2O5 than that on ITO regardless of work functions of the substrates. We also determined the complete energy level diagrams of C60/ZnPc on V2O5 and ITO. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a fully transparent nonvolatile resistive polymer memory device based on an anthracene-containing partially aliphatic polyimide along with indium tin oxide (ITO) top and bottom electrodes. High transmittance of over 90% in the wavelength range of 400 to 800 nm is accomplished with an ITO/polyimide/ITO/glass device. The device shows unipolar write-once-read-many times (WORM) memory behavior with an ON/OFF current ratio of ∼2 × 103, and the ratio remained without any significant degradation for over 104 s. The memory behavior of the device is considered to be governed by trap-controlled space-charge limited conduction (SCLC) and local filament formation. Based on molecular simulation of the polyimide, the location of energy states is different from that in the conventional charge transfer (CT) mechanism. Despite the relatively low ON/OFF current ratio, our results can give insight into the development of fully transparent memory device. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 918-925 [ABSTRACT FROM AUTHOR]