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Purpose: Here, we report a case of benign concentric annular macular dystrophy associated with a visual field defect.Case summary: A 34-year-old woman presented with a visual field defect that was not accompanied by a deterioration in visual acuity. The patient’s best-corrected visual acuity was 1.25 in both eyes. No signs of anterior chamber inflammation were observed, and fundoscopy showed annular hypopigmentation at the fovea in both eyes. Annular hyperfluorescence was observed on fluorescein angiography due to the window defect. Automated perimetry demonstrated an annular paracentral scotoma in both eyes. The standard electroretinogram was normal, whereas optical coherence tomography showed a loss at the inner and outer boundaries of the foveal photoreceptors. The patient had no history of chloroquine or hydroxychloroquine intake, which excluded Bull’s eye maculopathy. The patient was observed without treatment for 2 years and no change was observed in her visual acuity or the appearance of the fovea.Conclusions: Benign concentric annular macular dystrophy should be considered in patients with annular hypopigmentation at the fovea without deterioration in the visual acuity of both eyes.

Purpose: To report a case of unilateral orbital lipoma in a 22-year-old woman after an autologous fat graft.Case summary: A 22-year-old woman visited our clinic with the chief complaint of persistent ptosis of the left upper eyelid for 6 months. Five years prior, she had undergone double eyelid surgery on both eyes, in which autologous fat grafting was performed. She had experienced swelling of the left upper eyelid that began 6 months prior to her visit. Examinations of her visual acuity, intraocular pressure, pupil reflex, extraocular movement, and fundus revealed no abnormal findings. Sagittal images from orbital contrast computed tomography scans revealed a translucent lesion in the posterior space of the orbital septum of the left upper eyelid. Histological examination of excisional biopsy specimens showed mature adipose cells surrounded by a fibrous capsule. The patient remained disease-free at the 3-month follow-up.Conclusions: Lipoma can occur both during and after autologous fat grafting. It is important that the patient is well-informed of this issue before surgery and that the appropriate treatment is provided when it occurs.

Purpose: To investigate the effects of intravitreal bevacizumab injection combined with laser photocoagulation in patients with retinal microaneurysms.Methods: We retrospectively reviewed the medical records of 21 eyes of 21 patients who underwent intravitreal bevacizumab injection and/or laser photocoagulation to treat retinal macroaneurysms. Eleven eyes received the combination therapy (CT) and 10 eyes monotherapy (MT) (either bevacizumab injection or laser photocoagulation). Changes in visual acuity, central macular thickness, macroaneurysm size and location, blood pressure, and the lipid level were compared between the two groups.Results: The mean patient age was 74.0 ± 10.5 years and the mean study period 7.0 ± 5.3 months. The mean macroaneurysm diameter of the CT group was 480.00 ± 292.30 μm and that of the MT group 328.75 ± 87.09 μm. The diameter was significantly larger in the CT group (p = 0.002). The initial visual acuities were 0.91 ± 0.66 and 0.88 ± 0.83 in the CT and MT groups, respectively. At the 4-month follow-up, the visual acuities were 0.33 ± 0.26 and 0.17 ± 0.29 in the CT and MT groups, respectively, and had significantly improved only in the CT group (p = 0.042). The initial central macular thicknesses were 441.82 ± 226.81 and 541.63 ± 401.97 μm in the CT and MT groups, respectively. At the 4-month follow-up, the figures were 293.60 ± 46.10 and 269.00 ± 48.34 μm in the CT and MT groups, respectively, and had significantly decreased only in the CT group (p = 0.043). Compared to the initial findings, the proportion of patients whose final visual acuities improved by more than two lines were 73% and 40%, respectively, thus significantly higher in the CT group (p < 0.001).Conclusions: Combined intravitreal bevacizumab injection and laser photocoagulation treatment of retinal macroaneurysms improve visual acuity and decrease macular thickness.

To elucidate the differences in muscle bundle and satellite cells in medial rectus muscle through histological and Immunofluorescence studies of intermittent exotropia patients and normal controls....

Purpose This study aims to provide an automatic strabismus screening method for people who live in remote areas with poor medical accessibility. Materials and methods The proposed method first utilizes a pretrained convolutional neural network-based face-detection model and a detector for 68 facial landmarks to extract the eye region for a frontal facial image. Second, Otsu’s binarization and the HSV color model are applied to the image to eliminate the influence of eyelashes and canthi. Then, the method samples all of the pixel points on the limbus and applies the least square method to obtain the coordinate of the pupil center. Lastly, we calculated the distances from the pupil center to the medial and lateral canthus to measure the deviation of the positional similarity of two eyes for strabismus screening. Result We used a total of 60 frontal facial images (30 strabismus images, 30 normal images) to validate the proposed method. The average value of the iris positional similarity of normal images was smaller than one of the strabismus images via the method (p-value Conclusion The experimental results of 60 images show that the proposed method is a promising automatic strabismus screening method for people living in remote areas with poor medical accessibility.

Objectives To identify the relationship between surgical success rate and preoperative nasal mucosal thickness around the lacrimal sac fossa, as measured using computed tomography. Methods We reviewed 33 eyes from 27 patients who underwent endoscopic dacryocystorhinostomy after diagnosis of primary nasolacrimal duct obstruction and who were followed-up with for at least six months between 2011 and 2014. We measured preoperative nasal mucosal thickness around the bony lacrimal sac fossa using computed tomography and analyzed patient measurements after classifying them into three groups: the successfully operated group, the failed operation group, and the non-operated group. Results Surgery failed in six of the 33 eyes because of a granuloma at the osteotomy site and synechial formation of the nasal mucosa. The failed-surgery group showed a clinically significantly greater decrease in nasal mucosal thickness at the rearward lacrimal sac fossa compared with the successful-surgery group. However, nasal mucosal thickness of fellow eyes (i.e., non-operated eyes) was not significantly different between the two groups, and the location of the uncinate process did not appear to influence mucosal thickness. In the failed group, posteriorly located mucosal thickness of operated eye fossa was thinner than that of the non-operated eyes, but not significantly so. Conclusions Our results from this quantitative anatomical study suggest that nasal mucosal thickness is a predictor of endoscopic dacryocystorhinostomy results.

In this paper, we fabricated In0.53Ga0.47As-on insulator (OI) MOSFETs on Si substrates with different doping types to mimic ground plane doping using direct wafer bonding and epitaxial lift-off (ELO) techniques. We investigated the impact of doping types on the ground plane and the backgate biasing, which are important and preferable components in monolithic 3-D (M3D) integration, on the electrical properties of MOSFETs, such as the threshold voltage ( ${V} _{T}$ ) and the effective mobility ( $\mu _{\textsf {eff}}$ ). It was found that ${V} _{T}$ and $\mu _{\textsf {eff}}$ were significantly modulated by the backsubstrate doping and the backbiasing. These observations were explained by the change of carrier distributions, which were confirmed by technology computer-aided design simulation. Furthermore, we investigated the reusability of InP donor substrates for sequential epitaxial growth after ELO process toward a cost-effective M3D integration with the In0.53Ga0.47As channel.

Epitaxial Ge layers have been grown on Si (001) substrates by metalorganic chemical vapor deposition (MOCVD) using an isobutylgermane (IBuGe) metalorganic source. Low and high temperature two-step growth and post annealing techniques are employed to overcome the lattice mismatch problem between Ge and Si. It is demonstrated that high quality Ge epitaxial layers can be grown on Si (001) by using IBuGe with surface RMS roughness of 2 nm and an estimated threading dislocation density of 4.9 × 107 cm −2. Furthermore, single-junction Ge solar cells have been directly grown on Si substrates with an in situ MOCVD growth. The epitaxial Ge p-n junction structures are investigated with transmission electron microscopy and electrochemical C-V measurements. As a result, a power conversion efficiency of 1.69% was achieved for the Ge solar cell directly grown on Si substrate under AM1.5G condition.

Defect less semiconductor-on-insulator (-OI) by a cost-effective and low-temperature process is strongly needed for monolithic 3-D integration. Toward this, in this paper, we present a cost-effective fabrication of the indium gallium arsenide-OI structure featuring the direct wafer bonding (DWB) and epitaxial lift-off (ELO) techniques as well as the reuse of the indium phosphide donor wafer. We systematically investigated the effects of the prepatterning of the III–V layer before DWB and surface reforming (hydrophilic) to speed up the ELO process for a fast and high-throughput process, which is essential for cost reduction. This method provides an excellent crystal quality of In0.53Ga0.47As on Si. Crystal quality of the film was evaluated using Raman spectra, and transmission electron microscope. Finally, we achieved good electrical properties of In0.53Ga0.47As-OI metal-oxide-semiconductor field-effect-transistors fabricated through the proposed DWB and ELO.

A concentrating photovoltaic (CPV) cell exhibits the highest conversion efficiency among any solar cells. However, the further enhancement of the CPV efficiency is strongly limited by the heat generation at high solar concentrations. Here, we demonstrate a concentrating photovoltaic/thermoelectric hybrid generator using a single-junction, GaAs-based solar cell and a conventional thermoelectric module as a model system. Our hybrid generator gives rise to the conversion efficiency larger than the single CPV cell by ~3% at the solar concentration of 50 suns. Controlling thermal flow in the hybrid generator and the Peltier cooling effect is the key to achieving high efficiency. Our result provides a framework for designing a highly-efficient hybrid generator using both photo-electric and photo-thermal effects for the clean-energy production.

Single-junction Ge solar cells have been epitaxially grown on GaAs (001) substrates by a low pressure metalorganic chemical vapor deposition using isobutylgermane. Various growth conditions have been studied to reduce the high doping level of over 1×10 19 cm −3 of the p-type Ge epitaxial layer, which is detrimental to the minority carrier collection efficiency. By increasing the growth rate and employing a discontinuous doping technique, the p-type doping level of the epitaxial Ge layer has been lowered to 2×10 18 cm −3 , and the hole mobility increased from 44 to 162 cm 2 /V s. A high power conversion efficiency of 6.72% can be achieved under AM1.5 G illumination by the epitaxial Ge solar cell with the lowered doping level in the p-type Ge base region. The spectral response of the epitaxial Ge solar cell with a 5 µm thick base layer is good enough to use for InGaP/GaAs/Ge triple-junction solar cells.

Single-junction p–i–n InGaP solar cells are grown at various temperatures from 620 to 700 °C by low pressure metalorganic chemical vapor deposition on GaAs (001) substrates. The short circuit current density of the p–i–n InGaP solar cells increases by up to 38.8% when the growth temperature is reduced from 700 to 620 °C, while the open circuit voltage and fill factor show relatively small changes. The external quantum efficiency, especially, in the wavelength regime below 500 nm, is improved for the p–i–n InGaP solar cells grown at lower temperatures. The improvement might be attributed to the reduced absorption loss of the photons in the n-InGaP emitter region. The highest conversion efficiency of 11.01% is attributed from the p–i–n InGaP solar cell grown at 640 °C. Electron mobility and concentration of undoped InGaP layers are investigated as a function of the growth temperature and correlated with the p–i–n InGaP solar cell performance.

We present the heterogeneous integration of GaAs a single-junction solar cell (SC) on copper (Cu) via electroplating and epitaxial lift-off. We characterized the layer quality and the residual strain of the transferred SC layer through X-ray diffraction measurements and Raman spectroscopy. These results indicated that the fabrication process of SCs was quite stable, providing a high-quality film with a relatively small residual compressive strain. The SC transferred on Cu showed a highenergy conversion efficiency of 19.6% at 1sun illumination. In addition, we obtained a peak energy conversion efficiency of 20.8% at 2.5 suns in a solar concentrator.

We investigated the effect of growth temperature on the structural and electrical properties of InAlAs layers grown on InP (1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD) method. Flat surface morphology of InAlAs layers with root mean square (RMS) surface roughness values below 0.4 nm were obtained at 500 °C and 660 °C, while RMS surface roughness values of InAlAs layers grown in the region of intermediate temperature increase from 0.7 nm at 540 °C to 3.9 nm at 620 °C with increasing growth temperature. This increase in surface roughness is caused by the phase separation of the InAlAs layer, which is divided into In-rich and Al-rich column regions. The resistivity values of the InAlAs layers grown at 500 °C and 660 °C, in which the phase separation was not observed, were analyzed by the transmission line method (TLM) and those values were ~1 × 104 Ω·cm and 0.06 Ω·cm, respectively. We propose that oxygen atoms being incorporated into InAlAs layers during growth were the cause effect explaining the change in resistivity depending on the growth temperature. In order to evaluate high-resistivity InAlAs layers grown at 500 °C for a buffer layer of devices, we fabricated InGaAs-channel metal oxide field effect transistors (MOSFETs). The on/off current ratio values obtained from ID-VG transfer measurement was a value of 6.10 × 105, indicating a high-performance characteristic.

InAs nanowires (NWs) were selectively grown on hole patterned InP (1 1 1)B substrate by Metal-Organic Chemical Vapor Deposition (MOCVD). This study reports the vertical growth behavior of InAs NWs transitioned at a certain height and its difference under various growth conditions. This certain height is referred as “critical height.” This is a boundary where both vertical and lateral growth occur. Under this height, only vertical growth takes place. Vertical growth characteristics were reported through the determination of the critical height of NWs. The critical height was investigated for its three growth conditions; growth temperature, molar flow rates of In and As sources. Increase in growth temperature induced increase in critical height. Increase in growth temperature enhances the mobility of In adatom. This further increases diffusion length on the sidewall surface. However, increased AsH3 molar flow rate decreased the critical height. The surface reaction of In adatoms on the top (1 1 1)B surface of InAs NWs was reduced by the formation of As trimer. As a result, reduced relative vertical growth rate decreased the critical height of InAs NWs. The critical height of InAs NWs, however, was not changed by the variation of the Tri-Methyl Indium (TMIn) molar flow rate. This variation doesn’t affect the mobility of In adatom on the sidewall surface or the surface reaction rate on the top (1 1 1)B surface of NWs. Hence, we concluded that variation of the mobility of In adatom on the sidewall surface and relative vertical growth rate affect the critical height of InAs NWs.

Tellurium (Te) doping of InGaP with diethyl Te (DETe) was investigated to apply for tunnel junctions (TJs) in multijunction solar cells. When the DETe flow rate was 2 sccm, the electron concentration was found to increase with decreasing growth temperature. The obtained electron concentration reached up to $\sim 1 \,\, \times \,\, 10^{19}$ cm $^{-3}$ . The photovoltaic (PV) properties of InGaP/InGaAs/Ge triple-junction solar cells with a Te-doped InGaP layer in TJ were measured under concentrated light condition. Here, Te-doped InGaP layers in TJ were prepared using different growth temperatures ranging from 540 °C to 660 °C. Compared with other samples, open-circuit voltage ( $V_{\mathrm{ OC}})$ , fill factor, and conversion efficiency were higher for the sample with an InGaP grown at 570 °C. For this sample, external quantum efficiency was also found to be higher than the other samples, associated with the improved crystalline quality.

Heavily tellurium (Te)-doped InGaP layers in tunnel junctions (TJs) grown by using metalorganic chemical vapor deposition (MOCVD) were investigated to improve the device performance of InGaP/InGaAs/Ge triple-junction solar cells. Three different doping techniques were employed to grow the Te-doped InGaP layers in the TJ; Te doping, Te and Si co-doping and Te pre-doping. Compared to other samples, the external quantum efficiency (EQE) profiles in the InGaP top cell were found to be higher for the sample with Te pre-doping. Under a concentrated light condition, higher fill factor (FF) and conversion efficiency were also observed for the sample with Te pre-doping. These indicate that the crystalline qualities of the upper TJ, composed of a p-GaAs/n-InGaP TJ, and the InGaP top cell were improved by using the Te pre-doping method.

In this work, we developed wafer bonding techniques to bond GaAs and Si wafers. Wafer bonding was carried out at room temperature without high temperature annealing processes. The bonded interface showed a low interface resistance of 8.8×10−3 Ω cm2. We also exploited the new bonding techniques to fabricate a GaAs solar cell on a Si substrate. The solar cell showed a high energy conversion efficiency (13.25%) even without an anti reflection coating. The performance of the fabricated GaAs/Si solar cell was comparable to that of a homogeneous GaAs solar cell grown on a GaAs substrate. *Corresponding author.

In this paper, we present GaAs solar cells on Si substrate by direct epitaxial growth of III–V layers on Si substrate. Fabricated solar cells have shown relatively high energy conversion efficiency of 11.17% without anti reflection coating. By analyzing external quantum efficiency, dark I–V characteristics, and photo luminescence spectra, we have found that possible defect state near the band edge strongly impact on the performance of GaAs solar cell on Si and termination of these defects will further improve the performance of GaAs solar cell directly grown on Si substrates.

Graded doping techniques have been studied to improve the power conversion efficiency of the InGaP/InGaAs/Ge solar cells. We have investigated the efficiency enhancement of the triple-junction solar cells with gradually doped p-n junction active layers. The triple-junction epi-structures are grown by metalorganic chemical vapor deposition on Ge (100) substrates. The photovoltaic devices are fabricated and characterized under AM1.5 global illuminations. It was found that the graded doping profiles in InGaP emitter and InGaAs base layers can contribute to the efficiency improvement of the InGaP/InGaAs/Ge solar cells. The open circuit voltage and the short circuit current were improved up to 3.7 and 1.3%, respectively, by employing the graded doping technique.

As an effort to improve the conversion efficiency of InGaP/InGaAs/Ge triple junction solar cells, we investigated the effect of AlGaAs barrier layer on the cell performance under concentrated light condition. Three different solar cells having upper tunnel junctions (TJs) as n ++ -GaAs/p ++ -AlGaAs layers, n ++ -GaAs/p ++ -GaAs layers and n ++ -GaAs/p ++ -GaAs/p ++ -AlGaAs layers were prepared. Under concentrated light condition, open-circuit voltage ( V OC ), fill factor (FF) and conversion efficiencies were higher for the sample with an AlGaAs barrier layer than the samples without an AlGaAs barrier layer. For the sample with an AlGaAs barrier layer, external quantum efficiency was higher than other two samples. Most of all, the sample with a TJ as n ++ -GaAs/p ++ -GaAs layers showed a very poor electrical performance, which was associated with an imperfect crystalline quality of the InGaP top cell layers.

After growing InGaP/InGaAs/Ge triple-junction solar cells, we prepared two different Ge cells by etching down to the GaAs buffer layer (sample A) and the AlGaAs layer (sample B). Then, the photovoltaic properties of these two Ge cells were investigated under various light concentrations in order to find the factors affecting the overall performance of the triple-junction solar cells. Under concentrated light, the open-circuit voltage (V OC ), fill factor and conversion efficiency were higher for sample A than for sample B. The external quantum efficiency was shown to have a slightly higher value for sample A. Both the tunnel junction layer and the top contact resistance increased the series resistance, which also provided defects acting as leakage path. A comparison to previous works suggests that the conversion efficiency of Ge bottom, if present, is degraded marginally after the growth of the full structure of triple-junction solar cells.

We investigated the effect of antireflection (AR) coatings on the performance of high-power red laser diodes (LDs). The AR coating at the front facet and the high reflection (HR) coating at the rear facet were deposited on cleaved facets. As an AR coating, SiO2 or Si3N4 single layers with different thicknesses were employed. When the reflectivity of the AR coating was 25%, the best LD performance was obtained. The fitting to the threshold current density vs. effective optical length plot produced a transparent current density of 310 A/cm2. Under continuous wave (cw) operation at 15 °C, the operating current was 1.41 A, and the operating voltage was 2.33 V with an optical output of 280 mW. At an operating temperature of 0 °C, we observed the maximum output power of about 390 mW.

InGaAsNSb/Ge (1.14/0.67 eV) double-junction solar cells have been grown by metalorganic chemical vapor deposition (MOCVD). Ge p–n junction structures are realized by phosphorous diffusion on p-type Ge substrates. GaAs/InGaAsNSb heterojunction structures are grown on the Ge solar cells. The single-junction InGaAsNSb and Ge subcells are electrically connected by a GaAs tunnel junction. The fabricated solar cell exhibits an efficiency of 9.05% under AM 1.5G illumination with an open circuit voltage of 0.92 V. The InGaAsNSb subcell possessed a low external quantum efficiency over the sub-GaAs bandgap spectral range, reflecting the short minority carrier diffusion length of the dilute-nitride-antimonide material.

Metamorphic InGaAs laser power converters have a great potential to be used for a delivery of electrical energy over distances of centimeters up to kilometers. The direct band gap InGaAs material covers monochromatic wavelengths around 1100 nm, which can be supplied by widespread commercial lasers. In this study, the InGaAs-based laser power converter have been designed to absorb a laser at 1080 nm and grown by metalorganic chemical vapor deposition. Step graded InAlGaAs buffer layers were employed to overcome the lattice mismatch problem between InGaAs and GaAs. Various epitaxial growth conditions such as overshoot layer which contains higher indium composition than the final buffer layer, back surface field barrier, growth temperature and V/III ratio were studied to obtain high quality InAlGaAs metamorphic buffer. The fabricated InGaAs-based laser power converter, which had an enhanced metamorphic buffer and 5 μm thick grid metal, showed a high external quantum efficiency of 82.16% at 1080 nm wavelength. As a result, a conversion efficiency of 37.87% was achieved under 1080 nm monochromatic light at a laser power density of 538 mW/cm2. Further improvements are expected when the device structure is modified to reduce the series resistance and the growth condition is optimized to increase the minority carrier life time.

We investigated the effect of Si diffusion on the optical properties of GaInP-AlGaInP multiple quantum wells (MQWs) grown at different growth temperatures. Photoluminescence (PL) measurements showed that the emission wavelength was shortened and the PL intensity decreased with increasing growth temperature. Secondary-ion mass spectroscopy (SIMS) measurements showed that the Si concentrations in the MQW active region were similar regardless of the growth temperature. Different growth temperatures of the MQW layers might give rise to different compositions in the MQW layers, resulting in different emission wavelengths. We also investigated the temper-aturedependent optical properties of MQW layers grown with different well thicknesses (6, 8, and 10 nm). For the sample with a well thickness of 10 nm, better crystalline quality, better GaInP-AlGaInP interfaces and higher activation energy were observed compared to other samples. However, the activation energies for all three samples were found to be smaller than the carrier confinement energy. The carrier loss in the GaInP-AlGaInP QW might be related to defects and impurities in the AlGaInP layer.

We investigated the deep level photoluminescence and cathodoluminescence emissions from GaInP grown on Ge and Ge-on-Si substrates by metal-organic chemical vapor deposition. Considering the interface condition after the growth of GaInP on Ge, we speculated that the P vacancies and/or Ge atoms from the underlying layer due to interdiffusion were responsible for the deep level emissions. Moreover, the anti-phase boundaries in GaInP, incompletely suppressed even when grown on off-axis Ge substrates, were also responsible for the deep level emissions.

Defect-less semiconductor-on-insulator (-OI) by a cost-effective and low temperature process is strongly needed for monolithic 3D (M3D) integration. Toward this, in this paper, we present a cost-effective fabrication of the InGaAs-OI structure featuring the direct wafer bonding (DWB) and the epitaxial lift-off (ELO) techniques as well as the re-use of the InP donor wafer. We systematically investigated the effects of the pre-patterning of the III-V layer before DWB, surface reforming (hydrophilic), and electro-chemical etching to speed up the ELO process for a fast and high-throughput process, which is essential for cost reduction. We also demonstrated the re-usability of the InP donor wafer. Finally, as a result of the high film quality of the InGaAs channel combined with DWB and ELO, fabricated InGaAs-OI MOSFETs show a record-high effective mobility of ∼2800 cm2/Vs among surface channel Ino.53Gao.47As MOSFETs reported so far.

A series of hierarchical ZnO-based antireflection coatings with different nanostructures (nanowires and nanosheets) is prepared hydrothermally, followed by means of RF sputtering of MgF2 layers for coaxial nanostructures. Structural analysis showed that both ZnO had a highly preferred orientation along the 〈0001〉 direction with a highly crystalline MgF2 shell coated uniformly. However, a small amount of Al was present in nanosheets, originating from Al diffusion from the Al seed layer, resulting in an increase of the optical bandgap. Compared with the nanosheet-based antireflection coatings, the nanowire-based ones exhibited a significantly lower reflectance (∼2%) in ultraviolet and visible light wavelength regions. In particular, they showed perfect light absorption at wavelength less than approximately 400 nm. However, a GaAs single junction solar cell with nanosheet-based antireflection coatings showed the largest enhancement (43.9%) in power conversion efficiency. These results show that the increase of the optical bandgap of the nanosheets by the incorporation of Al atoms allows more photons enter the active region of the solar cell, improving the performance.

Si-based integrated circuits have been intensively developed over the past several decades through ultimate device scaling. However, the Si technology has reached the physical limitations of the scaling. These limitations have fuelled the search for alternative active materials (for transistors) and the introduction of optical interconnects (called “Si photonics”). A series of attempts to circumvent the Si technology limits are based on the use of III-V compound semiconductor due to their superior benefits, such as high electron mobility and direct bandgap. To use their physical properties on a Si platform, the formation of high-quality III-V films on the Si (III-V/Si) is the basic technology ; however, implementing this technology using a high-throughput process is not easy. Here, we report new concepts for an ultra-high-throughput heterogeneous integration of high-quality III-V films on the Si using the wafer bonding and epitaxial lift off (ELO) technique. We describe the ultra-fast ELO and also the re-use of the III-V donor wafer after III-V/Si formation. These approaches provide an ultra-high-throughput fabrication of III-V/Si substrates with a high-quality film, which leads to a dramatic cost reduction. As proof-of-concept devices, this paper demonstrates GaAs-based high electron mobility transistors (HEMTs), solar cells, and hetero-junction phototransistors on Si substrates.

We investigated the doping profiles of Mg and Si dopants near the multiple quantum well (MQW) active region in 640-nm-band GaInP-AlGaInP red laser diodes (LDs). With a 200-nm-thick Mg diffusion barrier, optimal doping profiles were obtained with an Mg flow rate of 80 sccm. Without a Si diffusion barrier, significant Si diffusion into the MQW layers was observed even at the lowest Si flow rate of 25 sccm. A 100-nm-thick Si diffusion barrier effectively suppressed the Si diffusion into the MQW layers, resulting in improved laser performance. The results suggest that undoped diffusion barriers for Mg and Si dopants in AlInP cladding layers with optimal thickness will enhance the laser performance.

Carbon doping of GaAs using CBr"4 (carbon tetrabromide) in metal-organic chemical vapor deposition (MOCVD) was investigated to obtain very high and sharp doping profiles required for tunnel junction in tandem solar cells. It was found that the hole concentration increased with decreasing growth temperature and V/III ratio. Hole doping profiles versus distance from the sample surface showed that the hole concentration near the surface was very low in comparison with that far below the surface. As a post-growth treatment, CBr"4 was supplied during the cool down process and produced almost constant hole concentration of 1x10^2^0cm^-^3 regardless of the depth, when CBr"4 flow rate was 9.53@mmol/min. Based on these results, solar cells were fabricated using both carbon (C) and zinc (Zn) as a p-type dopant. It was shown that C doping exhibits higher efficiency and lower series resistance than those of Zn doping in GaInP/GaAs tandem solar cells.

The performance of GaInP/GaAs tandem solar cells with AlInP growth temperatures of 680 ℃ and 700 ℃ on n-type GaAs (100) substrate with 2° and 6° tilt angles has been investigated. The series resistance and open circuit voltage of the fabricated tandem solar cells are affected by the substrate tilt angles and the growth temperatures of the window layer when zinc is doped in the tunnel diode. With carbon doping as a p-type doping source in the tunnel diode and the effort of current matching between top and bottom cells, GaInP/GaAs tandem solar cell has been exhibited 25.58% efficiency.

Flexible thin film (In)GaAs solar cells are grown by metalorganic chemical vapor deposition on GaAs substrates and transferred to 30 μm thick Au foil by internal stress-assisted epitaxial lift-off processes. The internal stress is induced by replacing the solar cell epi-layers from GaAs to In0.015Ga0.985As, which has a slightly larger lattice constant. The compressive strained layer thickness was varied from 0 to 4.5 μm to investigate the influence of the internal stress on the epitaxial lift-off time. The etching time in the epitaxial lift-off process was reduced from 36 to 4 h by employing a GaAs/In0.015Ga0.985As heterojunction structure that has a compressive film stress of −59.0 MPa. We found that the partially strained epi-structure contributed to the much faster lateral etching rate with spontaneous bending. Although an efficiency degradation problem occurred in the strained solar cell, it was solved by optimizing the epitaxial growth conditions.

In this work, we fabricated the In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors (MOSFETs) with a MOS interface of Y2O3/In0.53Ga0.47As and recessed gate structure. We investigated the interfacial properties of the gate stack and the junction characteristics of the fabricated MOSFETs. Low subthreshold slope (SS = 110 mV/dec), high on/off current ratio (Ion/Ioff = 106), and high effective mobility of 1600 cm2/V·s were achieved in the MOSFETs at a sheet charge density (Ns) = 1.2 × 1012 cm−2. From the temperature dependence of I–V characteristics, the interface trap density was extracted to be Dit = 2.2 × 1011 cm−2·eV−1 with a negligible trap-assisted leakage current.

Using GaInP as a nucleation layer, the Ge bottom cell was fabricated with a proper junction depth in the p-n junction and this Ge bottom cell was used to grow GaInP/GaAs/Ge triple junction solar cells. Then, the growth temperature of p-type GaAs base layer in the middle cell was investigated as a means of improving the solar cell efficiency. The solar cell grown at 550°C produced the improved efficiency compared to that grown at 680°C. The result suggests that the growth temperature of GaAs base layer is an important factor to improve the cell efficiency, related to the thermal stability of previously formed bottom cells.

We investigated the optical and electrical properties of Si-doped polar (c-plane) and nonpolar (a-plane) GaN layers grown by metal-organic vapor phase epitaxy (MOVPE) using photoluminescence (PL) and Hall-effect measurements. For c-plane GaN, the dominant emission bands were related to band-acceptor and donor-acceptor transitions, and mobility was dominated by optical phonon and ionized impurity scattering at high and low temperature, respectively. For a-plane GaN, the dominant emission bands were related to extended defects such as basal stacking faults (BSFs) and prismatic stacking faults (PSFs) and mobility was dominated by the scattering mechanism due to dislocations.