Search

The electrical properties of WO3 thin films vary significantly depending on the growth conditions. In this work, the influence of O2 gas on the band gap of WO3 thin films during growth was investigated via electronic structure characterization using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES). A substantial decrease in the electrical conductivity of the WO3 films was observed with an increase in the O2 partial pressure during growth. Spectral differences in the peak energy and intensity were apparent for WO3 films grown under only Ar and those grown in Ar:O2. It is difficult to explain the acquired spectrum of WO3 with oxygen defects through the rigid-band model in terms of the simple addition of electrons to the conduction band of WO3. Our results show that an oxygen deficiency in WO3 moves the conduction band to the Fermi edge.

We investigated the use of a silver reflector embedded with Ni–Cu nanoparticles to achieve low resistance and high reflectivity in GaN-based flip-chip light-emitting diodes. Compared to a single layer of Ag, the NC-NPs/Ag reflector exhibits a higher light reflectance of ~90% at a wavelength of 450 nm, a lower contact resistance of 4.75 × 10−5 II cm2, and improved thermal stability after annealing at 400°C. The NC-NPs formed after the annealing process prevents agglomeration of the Ag layer, while also reducing the Schottky barrier height between the p-GaN layer and metal reflector. The LED fabricated with a NC-NPs/Ag reflector exhibited a forward-bias voltage of 3.13 V and an improvement in light output power of 36.6% (at 20 mA), when compared with the LED composed of a Ag SL. This result indicates that the NC-NPs/Ag reflector is a promising p-type reflector for high-intensity light-emitting diodes.

Graphene oxide (GO)–cysteamine–Ag nanoparticles (GCA)–silver nanowire (AgNW) fabricated by depositing GCA over sprayed AgNWs on PET films were proposed for transparent and flexible electrodes, and their optical, electrical, and mechanical properties were analyzed by energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, current-voltage measurements, and bending test. GCA–AgNW electrodes show optical transmittance of >80% at 550 nm and exhibit a high figure-of-merit value of up to 116.13 in the samples with sheet resistances of 20–40 Ω/◻. It was observed that the detrimental oxidation of bare AgNWs over time was considerably decreased, and the mechanical robustness was improved. To apply the layer as an actual electrode in working devices, a Pt/GO/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/GCA–AgNW/polyethylene terephthalate structure was fabricated, and resistive switching memory was demonstrated. On the basis of these results, we confirm that the proposed GCA–AgNW layer can be used as transparent and flexible electrode.

In this study, we propose a method to quantitatively analyze the concentration of VOCs adsorbed on zeolite filters via gas chromatography (GC). The sampled VOCs from the filters with ethanol as a solution were characterized using GC to determine the concentration of the adsorbed VOCs by comparing the areas of GC peaks of the detected VOCs and ethanol. The proposed method also enabled determination of the desorption (regeneration) conditions of the zeolite filters according to heating temperature and time for various VOCs. Repeated adsorption and desorption of VOCs on zeolite filters and GC analyses allow us to evaluate the durability and reusability of the filter and could help predict the lifetime of zeolite filters in practice.

We propose an Ag reflector layer with an AgCu alloy layer as a thermally reliable reflector for high power flip-chip and vertical light emitting diodes (LEDs). By annealing the deposited Ag and Cu layers, intermixed grains and grain boundaries from the alloyed AgCu layer were formed on the LEDs, and CuO nano dots precipitated at the grain boundaries. A thick AgCu layer was deposited to cover the AgCu alloy layer. The precipitation of the CuO nano dots at the grain boundaries suppressed Ag agglomeration, leading to enhanced light reflectance after the annealing process. Consequently, the alloyed AgCu/Ag reflector produced by annealing at a high temperature of 500 °C demonstrated a higher reflectance of 78% and a lower contact resistance of 7.0 × 10-5 Ω · cm2.

The interfacial electronic structure of a bilayer of fullerene (C60) and zinc phthalocyanine (ZnPc) grown on aluminum-doped zinc oxide (AZO) substrates has been evaluated by X-ray and ultraviolet photoemission 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 (EDHOMO − EALUMO) was determined and compared to that grown on an indium tin oxide (ITO) substrate. The EDHOMO − EALUMO value of the heterojunction on AZO was 1.4 eV, while that on ITO was 1.1 eV. This result is discussed in terms of the differences of the work function and resistivity of each transparent conductive oxide. We also obtained complete energy level diagrams of C60/ZnPc/AZO and C60/ZnPc/ITO.

2,6-Diaminoanthracene (AnDA)-functionalized graphene oxide (GO) (AnDA-GO) was prepared and used to synthesize a graphene oxide-based polyimide (PI-GO) by the in-situ polymerization method. A PI-GO nanocomposite thin film was prepared and characterized by infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and UV-visible spectroscopy. The PI-GO film was used as a memory layer in the fabrication of a resistive random access memory (RRAM) device with aluminum (Al) top and indium tin oxide (ITO) bottom electrodes. The device showed write-once-read-many-times (WORM) characteristics with a high ON/OFF current ratio (Ion/Ioff = 3.41 &times, 108). This excellent current ratio was attributed to the high charge trapping ability of GO. In addition, the device had good endurance until the 100th cycle. These results suggest that PI-GO is an attractive candidate for applications in next generation nonvolatile memory.

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.

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. 2015

We demonstrate the coexistence of the unipolar and bipolar switching behaviors in a single oxide resistive device composed of Pt-CuO0.8-W structure and we reveal the switching mechanism by the comprehensive analyses of both unipolar and bipolar switching behaviors. The observations suggest that the RESET (turning OFF) mechanism of unipolar and bipolar switching modes can be explained by a unified scheme. The results also elucidate that the SET (turning ON) process in bipolar mode is originated from by the drift of ions though charged vacancies, while the SET process in unipolar mode is explained by electron tunneling through vacancies. The proposed model successfully explains the observations of resistive switching of our device regardless of input voltage polarity and, more importantly, we propose a way to selectively choose one specific operation mode.

We propose a simple and efficient model using a phenomenological fitting parameter for current-voltage sweeps to describe vacancy dynamics in oxide resistive devices, and thereby to explain the relation between physical state and resistance in these devices. The fitting parameter serves as a figure of merit, describing a device’s capability for multibit operation. The understanding achieved through this model allows efficient evaluation of device performance factors including the maximum ON/OFF ratio and the multiresistance property.

In this report, we employ an Al-doped ZnO (AZO) layer as a resistive switching layer for transparent resistive switching random access memory devices. An Indium-Tin-Oxide (ITO)/AZO/ITO/glass device exhibits a transmittance of ∼80% (including a glass substrate) in the visible wavelength region and demonstrates reliable bipolar resistive switching behavior over d.c. 300 sweeping cycles with a low operation voltage and a very low variation in the switching threshold voltage. These results indicate that the AZO film is a promising transparent resistive switching layer.

A high on/off ratio in oxide resistive devices is preferable for use in memory storage, especially when multibit operations are possible. Here, we demonstrate the effect of vacancy density on resistance by using three different Pt-copper oxide-W devices with different vacancy densities in the oxide layer. We show that a higher vacancy density in the oxide layer can enhance the on/off resistance ratio and demonstrate the advantage of this ratio in the realization of multi-bit operation. Finally, we successfully explain the impact of the vacancy density in the oxide layer using a simple model.

We present the first demonstration of the environmental application of a polyimide film (Kapton) with patterned thru-holes as a novel, efficient, flexible, recyclable, and active particulate matter (PM) air filter. The Kapton air filter captures PM using micro-sized thru-holes and the strong electrostatic force because of its high work function. It is highly efficient, transparent, flexible, and heat-resistant. Furthermore, it can be recycled simply by washing it with tap water. The proposed PM filter is a promising candidate for use as a highly efficient and economical recyclable air filter for home appliances, such as air-purifiers, air-conditioners, and humidifiers, as well as industrial filtration systems.

We investigated the resistive switching behaviors of the metal–copper oxide–metal devices with the enhanced capability in terms of high speed and multi-bit operation. From the analysis of the normal and extended resistive switching behaviors, the voltage-induced resistive changes were modeled and the resistive switching polarity was explained. Also, we proposed and fabricated a dual vacancy-type device structure with an extended resistive switching behavior and demonstrated a high-speed implemental 2-bit multi-bit operation by controlling specifically switch-on voltage pulses.

The improvement of the optical output power of GaN-based light emitting diodes (LEDs) was achieved by a novel bi-layer transparent top electrode scheme. The proposed bi-layer structure is composed of a Ga-doped ZnO layer with nano-patterns obtained solely by wet etching process and an Indium Tin Oxide p-type transparent conducting electrode layer. We employed various wet-etching conditions to maximize light extraction efficiency and it was observed that the crystal morphologies of nano-patterns and optoelectronic properties are dependent on etching duration. Because of ITO under GZO layer, the current spreading was not affected even after formation of nano-patterned surface on the GZO layer by wet etching. Consequently, an enhancement of as high as 43.1% in optical output power at an injection current of 100 mA for the LED with nano-patterns wet-etched by 0.025% HCl for 30 seconds was realized without significant degradation in electrical property when compared to a reference LED.

We investigated the effect of the electrode on the resistive switching property of (Cu, Zn, Pt)-Cu2S-W structures to clarify the role of metallic ions and electrodes in forming conductive paths in solid-electrolytes and also to improve the switching property. Notably, Zn-Cu2S-W and Pt-Cu2S-W structures that lack of oxidizable metal electrodes exhibited bipolar switching characteristics, and practically preferable switching properties with appropriately higher a turn-ON voltage and resistance were achieved for Zn-Cu2S-W in comparison to Cu-Cu2S-W with too low turn-ON voltage. In contrast, the degrading evolution of switching was observed in Pt-Cu2S-W. A simplified but convincing model is also suggested and discussed to explain the observations.

The structural, electrical, and optical properties of e-beam and sputter-deposited Indium-Tin-Oxide (ITO) films on sapphire and p-GaN wafers, as well as the post-deposition annealing effect for light-emitting-diode applications, were analyzed and compared. The specific contact resistance of the sputtered ITO film on a p-GaN wafer was found to be slightly higher than that of the e-beam deposited ITO films. However, in general, the electrical, structural and optical properties of the sputtered ITO films that were annealed at comparably lower temperature are better than those of the e-beam deposited ITO films, which is the consequence of a larger average grain size. The sputtered ITO film that was annealed at 500°C demonstrated a resistivity of as low as 3.6 × 10−4 Ω·cm, along with a high transmittance of ∼98% at 450 nm.

The mammalian brain is far superior to today’s electronic circuits in intelligence and efficiency. Its functions are realized by the network of neurons connected via synapses. Much effort has been extended in finding satisfactory electronic neural networks that act like brains, i.e., especially the electronic version of synapse that is capable of the weight control and is independent of the external data storage. We demonstrate experimentally that a single metal–oxide–metal structure successfully stores the biological synaptic weight variations (synaptic plasticity) without any external storage node or circuit. Our device also demonstrates the reliability of plasticity experimentally with the model considering the time dependence of spikes. All these properties are embodied by the change of resistance level corresponding to the history of injected voltage-pulse signals. Moreover, we prove the capability of second-order learning of the multi-resistive device by applying it to the circuit composed of transistors. We anticipate our demonstration will invigorate the study of electronic neural networks using non-volatile multi-resistive device, which is simpler and superior compared to other storage devices.

We demonstrate ultra-high-resolution magnetic force microscopy images of perpendicular magnetic storage media using carbon nanotube probes coated by ferromagnetic Co 90 Fe 10 films (20, 30, 40, and 50 nm). By optimizing ferromagnetic film thickness (effective tip diameter), we obtained best magnetic domain image with an 40 nm-Co 90 Fe 10 -coated tip (50 nm tip diameter) about a lateral detect density of 1200 k flux per inch on perpendicular magnetic storage medium, one of the highest resolutions in MFM imaging reported for this material system and structure. The observed dependence of tip dimension on signal contrast and image resolution was successfully explained by a theoretical analysis indicating that the signal contrast, along with the physical probe-tip dimension, should be taken into account to design magnetic probes tips for high-resolution magnetic force microscopy.

A novel memory optical test solution is proposed and experimentally evaluated for at-speed DDR2-SDRAM test using a commercial automatic test equipment (ATE). Combination of an optical signal splitting scheme and SerDes (Serializer/De-Serializer) technique based on FPGA (Field programmable gate array) allows the high-speed multi-parallel memory test with reduced channel resources. Owing to the SerDes, optical fiber channels are reduced by more than 87 percent and the number of optical modules including transmitter/receiver dramatically decrease to 95 percent, compared with a conventional optical test interface system. Furthermore, the proposed system can optically expand the tester resource by 4 times using a 1 × 4 optical splitting scheme. We evaluated the signal integrity of 28 layer PCB operating at 3.125 Gbps with three-dimension electromagnetic simulation to obtain more reliable system for memory testing. Consequently, for the first time to the best of our knowledge, we realized an optical SerDes interconnect system for a memory test tester and demonstrated an actual write/read function test of DDR2-SDRAM.

Very efficient and reliable GaInP/AlGaInP red multiple-quantum-well laser diodes for recordable/rewritable digital versatile disc (DVD-R/RW) were successfully developed by low-damage fabrication. Because we adopted dry etching instead of conventional chemical wet etching for the steep ridge sidewalls of laser diodes (LDs), devices could be operated at a high output power over 200 mW at 70°C without showing any unstable higher-order transverse modes. In-situ monitoring tools in metal organic chemical vapor deposition (MOCVD) and dry etching were useful for controlling process parameters precisely, which enhances device characteristics and maintains the reproducibility of device fabrication. A very small beam aspect ratio of 1.78 with a very low vertical beam divergence angle of 15.3° at a high output power was achieved by optimizing the two-step n-cladding layer in our LD structures. These low values of the vertical beam divergence angle and aspect ratio are essential for minimizing the coupling loss between the LD and the objective lens in DVD pickups.

In this work we employed photoreflectance spectroscopy over the temperature range 11-300K to investigate the heterointerfaces of a strained piezoelectric InGaAs∕GaAs single quantum well structure grown on a (111)AGaAs 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 41A 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 interf...

We report the structural properties of strained InGaAs/GaAs double confinement quantum well (QW) structures grown on (1 1 1)A GaAs by metalorganic vapor phase epitaxy. The structures were extensively analyzed by photoluminescence (PL) spectroscopy, High-resolution X-ray diffractometry (HRXRD) and transmission electron microscopy (TEM). Excellent interfacial characteristics and uniformly strained structures with no compositional modulation were obtained for [1 1 1]A-oriented QWs with well widths of 65–100 A containing up to ∼20% In grown over a range of growth temperatures and V/III ratios. HRXRD analyses also show that the InGaAs well layers are pseudomorphic. A narrow PL full-width-at-half-maximum (FWHM) of 7 meV at 12 K was achieved for a QW structure grown at 630°C with a V/III ratio of 260. A monolayer (ML) analysis of PL FWHM data indicates a well width fluctuation of ±1 ML, which is consistent with TEM observations showing a well width fluctuation of less than ±2 ML. The well width fluctuation values of [1 1 1]A QWs are in the range of ±(1–2) ML for growth temperatures of 630°C and 680°C with V/III ratios between 105 and 260, while for simultaneously grown [1 0 0]-oriented structures the fluctuations are in the range ±2 to over ±4 ML, depending on the V/III ratio.

The piezoelectric (PE) and pyroelectric properties of strained (111)-oriented InGaAs layers have recently attracted interest because they provide additional device design parameters. However, there still exists a substantial uncertainty as to the value of the PE constant e 14 as well as the value and sign of the pyroelectric coefficient. We applied both photoreflectance and contactless electroreflectance (CER) spectroscopy to assess the PE and pyroelectric properties of a strained InGaAs/GaAs quantum well (QW) structure grown on a (111)A GaAs substrate by metal organic vapor phase epitaxy. Photoreflectance and CER spectroscopy provide information on high-order QW transitions as well as the Franz-Keldysh oscillations that develop in the presence of electric fields in the GaAs barriers and lead to an accurate determination of the temperature dependence of the PE field and constant e 14 . High-resolution X-ray diffractometry and transmission electron microscopy were employed to independently determine the structural parameters and verify the high crystal quality of the QW structure. We observed a linear temperature dependence of the PE field and e 14 in the range 25 - 300 K. To our knowledge, this is the first observation of the pyroelectric effect in strained InGaAs layers grown on (111)A GaAs substrates.

We investigated the temperature dependence of the piezoelectric constant e 14 , i.e. the pyroelectric effect, of various strained InGaAs/GaAs single- and multi-quantum wells embedded in p–i–n structures grown on (111)B GaAs substrates and diodes made from these structures. Both photoreflectance spectroscopy and differential photocurrent spectroscopy were applied to obtain e 14 over the temperature range 11–300 K. The values of e 14 for In x Ga 1− x As quantum well layers with x =0.12–0.21 were observed to increase with temperature, which is contrary to the expected dependence, and the strain-induced components of the pyroelectric coefficients were quantitatively determined. The dependence of the pyroelectric coefficient on In fraction is discussed.

In this work we used the differential photocurrent technique to measure the strain-induced piezoelectric field in pseudomorphic InxGa1−xAs/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.

Highly stable and flexible transparent electrodes are fabricated based on silver nanowires (AgNWs) on both polyethylene-terephthalate (PET) and polyimide (PI) substrates. Terahertz time domain spectroscopy (THz-TDS) was utilized to probe AgNW films while bended with a radius 5 mm to discover conductivity of bended films which was further analyzed through Drude-Smith model. AgNW films experience little degradation in conductivity (

We report the demonstration of multilevel operation using Cu/Cu-GeTe/W nonvolatile resistive memory devices for enhanced storage density. We incorporated Cu atoms into GeTe solid-electrolyte switching layers in Cu/Cu-GeTe/W nonvolatile resistive memory devices by applying a bias to the sample holder during a radio-frequency sputtering process. By analyzing the dependence of the device current (resistance) on both the pulse input voltage magnitude and width, we achieved four distinct resistance levels that correspond to the 2-bit operation of a single memory cell. Moreover, a model was suggested and discussed to account for the observed multibit operation.

In this paper we present a study on the MOVPE growth and optical evaluation of strained InGaAs/GaAs quantum well (QW) structures with In contents of 17% and 22% on [1 1 1]A-oriented GaAs substrates. QW structures grown under different growth conditions were extensively analyzed by means of Photoluminescence (PL) spectroscopy. The dependence of the PL intensity and linewidth on the growth temperature and In content are investigated and compared to simultaneously grown [1 0 0]-oriented structures. It is shown that excellent QW interfaces with only ±(1–2) monolayer roughness were achieved for the [1 1 1]A-oriented structures with 17% In using a wide range of growth temperatures (550–670°C), whereas the interfacial properties of the [1 0 0] samples significantly degraded as the growth temperature was increased. For a [1 1 1]A QW structure with 22% In the PL characteristics are similar to those obtained for the 17% In sample; on the contrary, for the companion [1 0 0] sample a strong degradation of its optical properties is observed.

In this paper we present the achievement of high-quality strained InGaAs/GaAs piezoelectric quantum wells embedded in a P-I-N structure which was grown on a (1 1 1)A GaAs substrate at a single temperature by atmospheric pressure metalorganic vapor-phase epitaxy. The growth conditions and the structural and optical properties of a 10-period multi-quantum well structure with an In content of 13% in the wells are presented. High-resolution X-ray diffractometry studies show good crystalline and interfacial quality, as well as good repeatability of the quantum well parameters. A photoluminescence full-width at half-maximum value of 11 meV at 12 K was determined for the principal quantum well interband transition. A monolayer analysis of the principal optical transition, which includes the piezoelectric field, indicates a well width fluctuation of less than ±1 monolayer over the 10 quantum well periods.

We report our recent results on the growth and properties of GaAs/AlGaAs and strained InGaAs/GaAs quantum well (QW) structures grown on (111)A GaAs substrates by atmospheric-pressure metalorganic vapor phase epitaxy. We have fabricated 25-period GaAs/AlGaAs multiquantum well structures with good crystal quality, high photoluminescence (PL) emission intensity and monolayer (ML) well width fluctuation. We also present the optical and piezoelectric properties of strained InGaAs/GaAs single quantum well structures grown on (111)A GaAs. Photoreflectance spectroscopy has been performed to analyze not only the excitonic transitions, but also the Franz-Keldysh oscillations to obtain the electric fields in the well and barriers, which are necessary to determine the actual QW potential profile and, thereby, to properly interpret the properties of the structures. A PL linewidth of 9.7 meV has been also achieved, which corresponds to a 1 ML interfacial roughness for an In0.14Ga0.86As well with a 40 Å width.

We review the recent advances in the fabrication and properties of GaAs/AlGaAs and InGaAs/GaAs quantum well (QW) structures grown on (111)A GaAs substrates by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE). We show that a 25-period GaAs/AlGaAs multi-QW (MQW) structure was fabricated with good crystal quality, high photoluminescence (PL) emission intensity and monolayer (ML) interfacial roughness. A PL full width at half maximum (FWHM) of 10.5 meV was achieved for a 25-period MQW with a well width of 44 A. This is the narrowest linewidth reported to date for any similar structures grown on (111)A or B substrates by any growth technique. We also report the properties of an InGaAs/GaAs single quantum well structure grown on (111)A GaAs. For this structure, the PL FWHM value was 9.1 meV, corresponding to a 1 ML interfacial roughness for a well width of 41 A. This is the first demonstration of an InGaAs/GaAs quantum well structure grown on (111)A or (111)B GaAs by MOVPE.

We report an improved optical pumping efficiency in a vertical-external-cavity surface-emitting laser (VECSEL) by employing the double-band mirror (DBM), which acts as a pump beam reflector as well as a cavity mirror. The optical pumping efficiency of a VECSEL with the DBM was increased by 23%, as compared to one with the conventional distributed Bragg reflector. It was found that the use of the DBM was more effective in the VECSEL with the shorter absorption layer thickness.