AlGaInP Research Articles

Numerical Study on the Optical Properties of III-V Quaternary Compounds Aluminium Gallium Indium Phosphide Light Emitting Diode

The research works the quaternary compounds of AlGaInP (Aluminium Gallium Indium Phosphide) LEDs that provide luminescence intensity in high-brightness LEDs. AlGaInP LEDs, which are direct bandgap semiconductors with green color emission and a wavelength ranging from 500 to 565 nm, are important in electronics display and liquid crystal backlight applications. Depend on carrier concentration, the desired colors and luminescence intensity, the mole fraction of the quaternary compound is changed and also the bandgap energy. The paper contributions the carrier distribution of holes and electrons, the density of states, and the fermi-dirac distribution function calculated. Based on the carrier concentration, luminescence intensity versus photon energy has been determined. These simulation results are presented using MATLAB simulation with theoretical approach.

Epitaxial analysis of GaInP/AlGaInP red light-emitting diodes with ternary AlGaP quantum barriers for quantum efficiency enhancement

We have numerically analyzed Gallium Indium Phosphide (GaInP)/Aluminum Gallium Indium Phosphide (AlGaInP) red light-emitting diodes (LEDs) by utilizing ternary Aluminum Gallium Phosphide (AlGaP) quantum barriers instead of the conventional quaternary AlGaInP quantum barriers. The simulation findings show that the use of AlGaP quantum barriers in AlGaInP red light-emitting diodes leads to a significant increase in both electron and hole concentration in the quantum wells which in turn enhances the rate of radiative recombination compared to conventional (reference) red light-emitting diodes. Furthermore, the proposed LEDs have a substantial decline in efficiency droop from 38% to 32%.

Sheet Resistance Optimization in (Al)GaInP Solar Cells for Concentrator Quadruple–Junction Solar Cells

The reduction of the series resistance in multi‐junction solar cells is of high importance for attaining peak efficiencies in concentrator photovoltaics. This study showcases strategies to reduce the sheet resistance of the uppermost subcell of a direct wafer bonded four–junction devices, since it contributes significantly to the series resistance. Therefore, electron mobilities in n–type AlGaInP, lattice matched to GaAs, are investigated across bandgap energies between 1.9 and 2.1 eV and various doping concentrations. The sheet resistances for AlGaInP rear heterojunction cells are determined for the integration in a two terminal four‐junction solar cell. The rear heterojunction cell architecture effectively addresses the sheet resistance optimization because it features a thick n‐type doped absorption layer. The sheet resistance of our current world record quadruple‐junction solar cell with 47.6% efficiency under the 665‐fold concentrated AM1.5d spectrum is 550 Ω sq−1. Herein, it is shown that optimizing the n‐absorption layer in the 1.90 eV GaInP top cell can reduce the sheet resistance to 250 Ω sq−1 without deteriorating the short–circuit current density and current matching. This reduction corresponds to a 5 mΩ cm2 improvement in specific series resistance, which would elevate the efficiency of this device to 48.2%.

Effect of barrier layer width on the optical and spectral properties of InAsP/AlGaInP quantum dot lasers

The barrier layer thickness separating the dot-in-well structure in optoelectronic devices plays a crucial impact on the performance of these devices. Here, we report the effect of the barrier width in quantum dot (QD) laser. Three series of InAsP QD lasers were papered with different barrier widths (i.e., 8, 16, and 24 nm) of (AlGa)InP. The samples were prepared by MOVPE at 730 °C. Data of threshold current density, Jth giving a lower Jth for 8 nm barrier width sample and it becomes more temperature dependency evident by a low value of characteristic temperature, To ≈ 77 k. Emission spectra of 2 mm long lasers showed a blue-shift by approximately 11 nm when the barrier width increased from 8 to 24 nm. The modal absorption study showed a decrease in the inhomogeneous broadening for 24 nm barrier width sample. Simulation results revealed an increase in the optical absorption cross-section, σo with increasing barrier width. These results showed that significant improvements in the spectral properties of the InAsP QD lasers can be made by altering the (AlGa)InP barrier width.

MOCVD growth and characterization of high efficiency (Al)InGaP solar cells for luminescent concentrators

The employment of Luminescent Solar Concentrators (LSCs) is a well known strategy for the integration of photovoltaic technologies in buildings. One of the main challenges in this area lies in the developement of effective solar cells, whose band gap and structures are adjusted to match the emisson peak of the related LSCs. The cells are placed at the edges of the concentrator plate and should be designed to benefit of quasi-monochromatic irradiation. In this work we investigate the growth and characterization of high-efficiency (Al)InGaP-based solar cells designed to be coupled with LSCs: their performance is evaluated upon variation of their structure and composition and compared with Si cell efficiency. In particular, by EQE theoretical simulations, we evidence how InGaP structures optmized for LSCs differ from those to be used under direct solar spectrum. Results obtained not only unveil the characteristics for an improved performance of the cells, but also represent an advance in the elucidation of the behaviour of InGaP-based devices in LSCs for future optimization.

Study of the Factors Limiting the Efficiency of Vertical-Type Nitride- and AlInGaP-Based Quantum-Well Micro-LEDs

The efficiency of micro-light-emitting diodes (μ-LEDs) depends enormously on the chip size, and this is connected to sidewall-trap-assisted nonradiative recombination. It is known that the internal quantum efficiency (IQE) of aluminum gallium indium phosphide (AlGaInP)-based red μ-LEDs is much lower than that of nitride-based μ-LEDs. To establish the major reasons giving rise to this huge IQE discrepancy, we examined the limiting factors in the two structures. For the nitride-based InGaN quantum wells, the influences of random alloy fluctuations were examined. A two-dimensional Poisson and drift-diffusion solver was applied to analyze these issues.

Gingival hyperplasia treatment using diode laser gingivectomy in a child with cerebral palsy: case report

Gingival hyperplasia is associated with several factors, such as chronic inflammation due to the large accumulation of biofilm and medications including anticonvulsants. The aim of this study is to report a clinical case of a 4-year-old spastic quadriplegic cerebral palsy patient with gingival hyperplasia in the palatal region of the upper teeth induced by the use of high doses of anticonvulsant medications. The patient attended the Dental Assistance Center for People with Disabilities, with fibrotic gingival hyperplasia in the upper posterior region, covering the dental crowns on the palatal and occlusal surfaces. Oral hygiene instructions were previously carried out using chlorhexidine gluconate solution (0.12%) on the teeth with the aid of a cotton swab, twice a day for seven days, to reduce bacterial plaque levels and control periodontal inflammation. Gingivectomy was performed using a gallium aluminum arsenide diode laser (GaAlAs; 808±10 nm, 2.5 W output power, continuous mode). Following the surgical procedures, photobiomodulation therapy was performed with a low-level aluminum gallium indium phosphide diode laser (InGaAlP; 660±10 nm, 100 mW, 3 J) at three points (anterior, middle and posterior region of surgical wound). The patient returned at 7 and 30 days after surgery presenting accelerated wound healing. It was concluded that the high-level diode laser associated with photobiomodulation therapy were effective for performing a conservative and safe procedure in a patient with severe neurological disorder.

AlGaInP optical source integrated with fiber links and silicon avalanche photo detectors in fiber optic systems

This study has clarified aluminium gallium indium phosphide (AlGaInP) optical source integrated with fiber links and silicon avalanche photodetectors in fiber optic systems. The output spectral power, rise time, signal frequency and resonance frequency for AlGaInP laser diode. The laser diode rise time, output spectral power and resonance/signal frequencies versus injection current and ambient temperatures are sketched. The silica doped germanium fiber link pulse broadening and the signal fiber bandwidth are investigated against temperature variations. The signal per noise ratio is related to Q value and bit error rate (BER) at the receiving point (Si avalanche photodetector (APD)) are sketched with temperature.

Structural design and performance improvement of flip-chip AlGaInP mini light-emitting diodes

Flip-chip (FC) aluminum gallium indium phosphide (AlGaInP) mini light-emitting diodes (mLEDs) with p and n lateral electrode structures and a larger light-emitting area have significant potential for integrating red, green, and blue mLEDs of locally dimmable zones for developing new-generation LED-backlit liquid crystal displays. Herein, an FC AlGaInP mLED having 9 × 6 mil dimensions is fabricated using wafer bonding and transfer technology methods. We propose a patterned n-gallium-arsenide (GaAs) epilayer by etching for ohmic contact and optimizing the specific contact resistance of an FC mLED. The light-output intensity images demonstrated that this etching process improved the uniformity of current distribution and matched the simulation results. Compared with conventional FC mLEDs, the output powers of FC mLEDs with a patterned n-GaAs layer increased from 3.4% to 4.5% and the wall-plug efficiency improved by 1.04%. Moreover, Ag was applied as a reflector on patterned n-GaAs rather than AuGe. The output power of FC mLEDs with an Ag reflector showed a 3.5%–8.2% improvement over FC mLEDs with an AuGe reflector. Finally, FC mLEDs that were encapsulated with epoxy and far-field radiation patterns indicated that packaged FC mLEDs had a smaller divergence angle and narrower viewing angle.

Giant and Anisotropic Nonlinear Optical Responses of 1D van der Waals Material Tellurium

AbstractRecently, tellurium (Te), composed of helical Te chains stacked via the van der Waals interaction, emerges as a versatile material with high carrier mobilities and intriguing topological properties. Here, it is revealed that Te's 1D counterpart, that is, Te nanowire (NW), has advantages over the NWs of other materials in the characteristics of giant and anisotropic nonlinear optical responses. This endows the Te NW with potentials for developing nonlinear photonic and optoelectronic nanodevices with high efficiency and polarization selectivity. Compared with the well‐studied III–V and II–VI compound NWs, such as aluminium gallium arsenide, zinc oxide, and indium phosphide NWs, second harmonic generations (SHGs) and third harmonic generations (THGs) from the Te NWs are more than two orders of magnitude stronger. Its second‐order nonlinear susceptibility is estimated as 1.25 × 104 pm V−1, which is the highest value in the reported NWs, and almost four orders of magnitude higher than ZnO NW. Further, this giant optical nonlinearity promises the realizations of strong SHGs and sum‐frequency generations from Te NWs with the pump of sub‐milliwatt continuous‐wave lasers. Determined by the helical Te chain, its SHG only responds to the pump laser polarized perpendicularly to the long axis of NW, which is opposite to the polarization dependencies in other NWs, and the THG has a distorted fourfold polarimetric pattern.

Treatment Using Low Level Laser Therapy in The Oral Manifestations of Steven Johnson Syndrome

This paper reports the objective intervention of the Hospital Dentistry team of the Beneficent Association of Campo Grande Santa Casa, contemplating a multi-professional approach to present Low-Level Laser Therapy (LLLT) as a therapeutic alternative for the treatment of individuals with Stevens-Johnson Syndrome (SJS). Male patient, 13 years old, with an initial complaint of pain, edema and burning mouth was treated by in situ applications of LLLT - Aluminium Gallium Indium Phosphide - InGaAlP type diode Laser (Laser duo / DMC Therapy XT, São Carlos, SP, Brazil), to promote photobiomodulation and subsequent repair of the compromised mucosa. Monitoring the patient during four laser therapy sessions with 24-hour intervals between them revealed a favorable evolution of the clinical picture with tissue repair, decreased pain and consequent oropharyngeal homeostasis. The favorable results consolidate LLLT as an alternative to be adopted with considerable effectiveness in combating pain and tissue changes in the oral mucosa resulting from the SJS.

Gigabit per second visible light communication based on AlGaInP red micro-LED micro-transfer printed onto diamond and glass.

Full-color smart displays, which act both as a display and as a high-speed visible light communication (VLC) transmitter, can be realized by the integration of red-green-blue micron-sized light emitting diodes (micro-LEDs) onto a common platform. In this work, we report on the integration of aluminum gallium indium phosphide red micro-LEDs onto diamond and glass substrates by micro-transfer printing and their application in VLC. The device on-diamond exhibits high current density and bandwidth operation, enabled by diamond's superior thermal properties. Employing an orthogonal frequency division multiplexing modulation scheme, error-free data rates of 2.6 Gbps and 5 Gbps are demonstrated for a single micro-LED printed on-glass and on-diamond, respectively. In a parallel configuration, a 2x1 micro-LED array achieves error-free data rates of 3 Gbps and 6.6 Gbps, on-glass and on-diamond, respectively.

Impact of photobiomodulation on the osseointegration around dental implants in fresh extraction socket: a 1-year split-mouth clinical trial

BackgroundLow-level laser therapy (LLLT) is a noninvasive technique that stimulates osteoblastic activity and enhances tissue healing. The goal of this trial was to assess the efficacy of LLLT on the osseointegration of implants placed on fresh extraction sockets.Patients and methodsA 1-year split-mouth controlled clinical study was conducted on 40 dental implants inserted immediately in 20 patients. Implants were randomly divided into two groups. Eight sessions of LLLT (a 660 nm aluminum gallium indium phosphide) were used to irradiate the test group implants during the first 2 weeks. A similar process was done for the control group implants using a laser headpiece that was adjusted in 'off' mode. Osseointegration was assessed by recording implant stability in addition to clinical and radiographical evaluations.ResultsThe statistical tests showed that there were no significant differences in the mean values of the primary outcome (implant stability measured by Periotest) between the test and control implants over time. Besides, no significant differences were observed between the study groups regarding the secondary outcomes which include marginal bone loss, probing depth, gingival index, modified plaque index, bleeding index, and pain on visual analog scale.ConclusionLLLT using a 660 nm aluminum gallium indium phosphide laser during the first 2 weeks following the immediate implantation in posterior mandible regions expressed no statistically significant impact on the osseointegration.

Reverse Heterojunction (Al)GaInP Solar Cells for Improved Efficiency at Concentration

Mitigating series resistance is crucial to the efficiency of concentrator solar cells at high current density. Conventional AlGaInP junction designs for the top junction of III-V multijunction cells present a challenging tradeoff between series resistance on the one hand and current collection and voltage on the other hand. In this article we discuss the physics of a reverse heterojunction solar cell that aims to improve on this tradeoff by combining a high bandgap Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.18</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.33</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.49</sub> P base and a lower bandgap (Al)GaInP emitter. The high mobility of the emitter leads to a relatively low series resistance, compared with a high bandgap homojunction cell. The electroluminescence spectrum shows emission peaks from both the emitter and base, leading to an open-circuit voltage that is not strictly dominated by either layer. The reverse heterojunction design is increasingly beneficial as the one-sun voltage increases.

Comparison and Evaluation of the Low-Level Laser and the Red and Blue LED Effects on Wound Healing in Rabbit.

Introduction: Wound healing is a dynamic, interactive process to achieve the restoration of skin integrity and proper function after damage. Applying a low-level laser (LLL) and light emitting diodes (henceforth LEDs) is introduced in previous studies to accelerate the process of wound healing. The aim of this study is to compare the effect of the LLL and LEDs on wound healing in rabbits. Methods: Full thickness same size square excision wounds were created on the dorsum of the rabbits. Twenty rabbits were randomly divided into four groups, according to the treatment received. Group 1: the AlGalInP (aluminium gallium indium phosphide) laser (4 J/cm²); group 2: the red LED (30 J/cm²); group 3: the blue LED (60 J/cm²) and group 4, as the control group, was not irradiated. After 30 days, the wounds were evaluated both morphologically and histopathologically. Statistical significance was defined as a P value of less than 0.05. Results: All interfering methods including the LLL and LEDs had better outcome compared with the control group of both sizes and histopathologic features. The red laser group showed better results compared to the control group and either the LED groups. Comparing LEDs, the red LED performed better than the blue LED. Conclusion: This study confirmed the significant effects of the LLL and LEDs on wound healing. Comparing the LLL and LED, the LED may be a better choice, especially for bedridden or debilitated patients. The LED may also more cost effective in wound healing in comparison with the LLL.

Design evolution of MOVPE reactors for improved productivity: Adaptation to nitrides and feedback to classical III-V

High growth rate of GaAs more than 90 μm/h is achieved in the attempt of the productivity improvement of solar cells. The design concept is derived from the MOVPE reactor for nitrides. The design criteria for nitride MOVPE reactor were found to be very useful for GaAs MOVPE. Originally, MOVPE reactors for nitrides were developed on the basis of the reactor design for classical III-V materials. Today, the principle of reactor design to cope with the singularity of nitrides brings about essential feedback to the next-generation reactors for classical III-V materials for improved productivity.At first, design criteria for GaN MOVPE reactor are described in light of the vapor phase reaction. Secondly, cost analysis of a 19 µm-thick GaN layer on a bulk GaN substrate for a vertical diode is briefly discussed in light of a trade-off between a high purity and a high growth rate of GaN.In GaAs-based solar cells, the thickness of light absorber is a couple of micrometers, accompanied by a thin (Al)InGaP cap, the growth time of which can be reduced to a few minutes if the growth rate is on the order of a few tens µm/h. In consideration of these factors, cost analysis of MOVPE for GaAs solar cells will be discussed in comparison with GaN on GaN diode.

Comparative Study of ∼2.05 eV Lattice-Matched and Metamorphic (Al)GaInP Solar Cells Grown by MOCVD

This work investigates two conceptually different approaches, both based on the AlGaInP alloy family, to produce metal–organic chemical vapor deposition grown 2.05 eV direct bandgap materials for use in the top cell of AM0 multijunction solar cells. The first approach achieves the target bandgap via (Al0.32Ga0.68) 0.52In0.48P lattice-matched to GaAs. The second approach achieves the target bandgap via relaxed, lattice-mismatched Ga0.66In0.34P. Solar cell characterization and analytical device modeling reveal merits and challenges for both approaches. Both devices are found to possess comparable minority carrier diffusion lengths within the p-type base and an equal bandgap-voltage offset of 0.54 V, suggesting effectively similar base material quality. However, the metamorphic Ga0.66In0.34P cell exhibits a superior quantum efficiency across all wavelengths, particularly at short wavelengths. Modeling results attribute the enhanced short wavelength response to the wider direct bandgap of the internally lattice-matched Al0.69In0.31P window and a longer emitter diffusion length. As such, despite the non-negligible lattice mismatch, the enhanced short wavelength response for the metamorphic Ga0.66In0.34P approach proved significantly advantageous, at least with respect to the growth conditions used in this study. Assuming the use of a perfect antireflection coating, the lower parasitic optical absorption from the wider direct bandgap window alone provides as much as ∼0.72 mA/cm2 additional photocurrent. Combined with the higher quality emitter layer observed in this study, ∼1.1 mA/cm2 additional photocurrent was achieved for the metamorphic Ga0.66In 0.34P approach. These values correspond to ∼3.9% and ∼6.0% of the total available photocurrent for a 2.05 eV bandgap solar cell.

Short-term evaluation of photobiomodulation therapy on the proliferation and undifferentiated status of dental pulp stem cells.

The aim of this in vitro study was to analyze the effect of photobiomodulation therapy (PBMT) on the proliferation and undifferentiating status of stem cell from human exfoliated deciduous teeth (SHEDs). PBMT was carried out with an aluminum gallium indium phosphide (InGaAlP) diode laser in contact and punctual mode (continuous wave, 660nm, 20mW, 0.028cm2, and average energy densities of 1 (1s), 3 (4s), 5 (7s), 10 (14s), 15 (21s), or 20 (28s) J/cm2 per point). The immunoprofile of the SHEDs was analyzed using flow cytometry. Cell proliferation was assessed by the MTT reduction assay. Gene expressions of mesenchymal stem cell markers (OCT4, Nestin, CD90, and CD105) were assessed by RT-qPCR 48h after PBMT. Data were compared by analysis of variance (ANOVA) and Tukey's test (p ≤ 0.05). Cells cultured under nutritional deficit and treated with PBMT at 5J/cm2 presented similar cell growth than those of positive control group. Cell growth was significantly higher than those of other groups. Mesenchymal stem cell gene markers were still expressed after PBMT at 5J/cm2. In a short-term analysis, PBMT increases the number of stem cells with no interference in the undifferentiated state of the irradiated cells, which opens wide possibilities for application in tissue regeneration.

(Al)GaInP/GaAs Tandem Solar Cells for Power Conversion at Elevated Temperature and High Concentration

We demonstrate dual-junction (Al)GaInP/GaAs solar cells designed for operation at 400 °C and 1000x concentration. For the top junction, we compare (Al)GaInP solar cells with room-temperature bandgaps ranging from 1.9 to 2.0 eV. At 400 °C, we find that ∼1.9 eV GaInP solar cells have a higher open-circuit voltage and a lower sheet resistance than higher bandgap (Al)GaInP solar cells, giving them a clear advantage in a tandem configuration. Dual-junction GaInP/GaAs solar cells are fabricated, and we show temperature-dependent external quantum efficiency, illuminated current–voltage, and concentrator measurements from 25 °C to 400 °C. We measure a power conversion efficiency of 16.4% ± 1% at 400 °C and 345 suns for the best dual-junction cell, and discuss multiple pathways to improve the performance further. After undergoing a 200 h soak at 400 °C, the dual-junction device shows a relative loss in efficiency of only ∼1%.

Wound-Healing potential of Sebastiania hispida (Mart.) Pax (Euphorbiaceae) ointment compared to low power laser in rats.

Impaired wound healing represents a serious complication in some pathologies and the use of plant extracts has proved to improve tissue repair. The objectives of this study were to evaluate the healing potential of the ointment of Sebastiana hispida compared with Aluminum-Gallium Indium-Phosphide Laser (InGaAlP) in surgically induced wounds in rats and to perform the phytochemical analysis. The phytochemical analysis was performed in the classic way and also by HPLC. A controlled study was developed with 80 rats (200-250 g) in which a linear excision was performed in the dorsal region after shaving, measuring 2 cm × 1 cm (epidermis and dermis) exposing the muscle fascia. The rats were randomly divided into four groups of twenty animals each. The experimental groups (n = 5) were G1 (Saline); G2 (crude methanol plant extract 2% + Carbopol Gel 98%); G3 (crude methanol plant extract 2% + lanolin/vaseline) and G4 (laser). The incision healing processes were monitored during 3, 7, 14 and until 21 days after excision. The histologic parameters evaluated were Collagen fiber types, microscopic examination and neovascularization. There was a significant increase in the deposition of collagen fibers, as evidenced by a better organized epithelial tissue, keratinized and showing greater proliferation of new blood vessels in the inflammatory phase in the group treated with both the extract and laser. The results were correlated to the phenolic derivatives found after qualitative and quantitative analysis. These compounds were considered responsible for the healing process. The topical treatment with S. hispida leaves, in the two different formulations, was more effective than the application of the laser (Ingan ALP) 660 nm in the model used.