Organic Vapor Phase Epitaxy Growth Research Articles

InGaAs quantum wells on wafer-bonded InP∕GaAs substrates

Wafer bonding and hydrogen implantation exfoliation techniques have been used to fabricate a thin InP template layer on GaAs with intermediate silicon nitride bonding layers. This template layer was used to directly compare subsequent metal organic vapor phase epitaxial growth of InGaAs∕InAlAs quantum-well structures on these wafer-bonded templates to growth on a standard InP substrate. Chemical mechanical polishing of the bonded structure and companion InP substrates was assessed. No effects from the coefficient of thermal mismatch are detected up to the growth temperature, and compositionally equivalent structures are grown on the wafer-bonded InP template and the bare InP substrate. However, after growth dislocation, loops can be identified in the InP template layer due to the ion implantation step. These defects incur a slight mosaic tilt but do not yield any crystalline defects in the epitaxial structure. Low-temperature photoluminescence measurements of the InGaAs grown on the template structure and the InP substrate exhibit near-band-edge luminescence on the same order; this indicates that ion implantation and exfoliation is a viable technique for the integration of III-V materials.

Ferromagnetic nanoclusters hybridized in Mn-incorporated GaInAs layers duringmetal–organic vapour phase epitaxial growth on InP layers under low growth temperatureconditions

We demonstrate the successful formation of ferromagnetic nanoclusters inMn-incorporated GaInAs layers grown by metal–organic vapour phase epitaxyon InP(100) substrates under low growth temperature conditions below450 °C. We find that MnAs nanoclusters with NiAs-type hexagonal crystallographic structures,which show ferromagnetic characteristics up to a relatively high temperature of about305 K, are formed near the layer surfaces of Mn-incorporated GaInAs layers grown at440 °C. After deposition of undoped InP layers on Mn-incorporated GaInAs layers,MnP nanoclusters with orthorhombic cubic crystallographic structures, in which7% arsenic is incorporated, are formed in InP layers. The samples with MnPnanoclusters show strong ferromagnetic coupling up to about 305 K, although theCurie temperature of MnP bulk compounds is 291 K. Energy dispersive x-rayspectroscopy (EDS) indicates that Mn concentrations in InP and GaInAs layers surroundingMnP nanoclusters are almost negligible. MnAs nanoclusters are also formed inMn-incorporated GaAs layers grown under low growth temperature conditions of450 °C on GaAs(100) substrates. From the results of magnetic characterizationswith respect to growth temperatures of the samples, we found thatall the Mn-incorporated GaAs layers grown at temperatures below450 °C showed ferromagnetic behaviour.

Epitaxially grown GaP/GaAs1−xPx/GaP double heterostructure nanowires for optical applications

We demonstrate metal organic vapour phase epitaxy growth ofGaP/GaAs1−xPx/GaP double heterostructure nanowires on GaP(111)B, and reportbright photoluminescence at room temperature. By using differentPH3 toAsH3 flow ratios duringgrowth of the GaAs1−xPx segment, we are able to control the composition of the segment, making it feasible to tunethe wavelength of the emitted light. A photoluminescence system was employed tocharacterize the luminescence, and x-ray energy dispersive spectrometry and x-raydiffraction studies were used to investigate the composition of the segment. Thesedouble heterostructure nanowires could in the future be used in optoelectronicdevices and as multiple-wavelength fluorescent markers for biomedical applications.

A two-step metal organic vapor phase epitaxy growth method for high-quality ZnO on GaN/Al 2O 3 (0 0 0 1)

High-quality [0 0 0 1]-oriented ZnO films were grown in a single growth experiment on GaN/Al 2O 3 applying a two-step metal organic vapor phase epitaxy growth technique. The essence of this method is the heteroepitaxy of a low-temperature ZnO buffer layer using dimethyl-zinc and tertiary-butanol precursors on GaN/Al 2O 3 and the subsequent homoepitaxial growth of a high-temperature layer using N 2O as O-precursor. The layers show smooth surface morphology and high crystalline quality as demonstrated by X-ray diffraction (FWHM of (0 0 0 2) ω-scans for a 2.28 μm thick layer is 160″). The bright luminescence is dominated by narrow excitonic emission lines (e.g., FWHM <1.3 meV for bound exciton I 8). Our method opens broad prospect for the growth of ZnO-based device structures.

Influence of growth kinetics on the indium distribution during MOVPE growth of GaInN quantum wells

The composition and thickness of GaInN quantum wells (QWs) determines the luminescence properties of GaInN/GaN-based optoelectronic devices. The In distribution is characterized by considerable inhomogeneities on two spatial scales. Variations of locally averaged In concentrations and QW thickness on a “large” scale of several 10 nm along the QW occur in addition to small clusters with high In concentrations up to 100% and sizes of only a few nanometers. In the present work, we investigated the influence of the growth rate during metal organic vapor phase epitaxy (MOVPE) growth on the In distribution. The composition of GaInN single QWs was determined by evaluating high-resolution transmission electron microscopy (HRTEM) lattice-fringe images. At low GaInN deposition rates, a significant increase of the inhomogeneity of the In distribution compared to a sample grown with a high rate was found. A good correlation between experimental and calculated photoluminescence energies is achieved. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Epitaxial growth of high-quality ZnSSe on ZnSSe/In/glass substrate

We have studied the metal–organic vapour phase epitaxy growth of ZnSSe on a ZnSSe/In/glass substrate. The ZnSSe/GaAs wafer was glued on an indium/glass substrate. Mechanical polishing and the etching solution of NaOH(1M):H2O2 (30%) = 4:1 was used for the removal of the GaAs substrate. The deterioration of the photoluminescence after etching is related to the surface defects originally existing at the interface of ZnSSe/GaAs and the roughening of the surface. The enhancement of the photoluminescence after surface trimming is due to the smoothness of the surface and due to the reflection of the indium mirror. The ratio of near-band emission to broad-band emission becomes higher after the regrowth of the ZnSSe epilayer on ZnSSe/In/glass substrate at 220 °C. The near-band emission was observed at 438 nm with a full width at half-maximum of 26.6 meV at 77 K. This means that a high-quality ZnSSe epilayer can be obtained on the ZnSSe/In/glass substrate.

InGaAs nano-pillar array formation on partially masked InP(111)B by selectivearea metal–organic vapour phase epitaxial growth for two-dimensional photoniccrystal application

We report on the selective area metal–organic vapour phase epitaxial growth of anInGaAs nano-pillar array on a partially masked InP(111)B substrate. Thistechnique is very promising as a way to form semiconductor two-dimensionalphotonic crystals (2DPCs) suitable for infrared optical fibre communication. Wesuccessfully formed uniform hexagonal 2DPCs having vertical (110) facet sidewallson 400 nm-pitch masked substrates. We observed vertical growth enhancement aswell as the lateral overgrowth suppression for high aspect ratio InGaAs nano-pillararray formation under high growth-rate, long growth-time, and narrowwindow-opening conditions. We verified infrared emission from the InGaAsnano-pillar array by low-temperature photoluminescence measurement.

Metal organic vapor phase epitaxial growth of heavily carbon-doped GaAs using a dopant source of CCl3Br and quantitative analysis of the compensation mechanism in the epilayers

Heavy carbon doping of GaAs by metal organic vapor phase epitaxy has been carried out using a dopant source of carbon trichloro bromide (CCl3Br), an intersubstituted compound of the two highly efficient dopant sources of CCl4 and CBr4. Results are being reported in the doping range of 1.76×1019–1.12×1020 cm−3, achieved at growth temperatures between 570 and 600 °C and V/III ratios between 10 and 50. The compensation mechanism of the carriers in the samples and its effect on the electrical and optical properties were systematically studied using double crystal x-ray diffraction, mobility, and photoluminescence measurements. A data analysis technique has been presented to quantitatively calculate the level of compensation in the layers from conventional lattice mismatch measurements. The antisite incorporation of carbon was found to be the dominant compensation mechanism for hole concentrations above 7.36×1019 cm−3. Room temperature mobility data of the samples showed a sharp deviation from the usual Hilsum’s fitting after the carrier concentration of 7.36×1019 cm−3, due to increased self-compensation of the epilayers. The optical properties of the samples were correlated to the self-compensation effect by the photoluminescence measurements carried out in the temperature range of 10–140 K.

Studies of MOVPE growth conditions for the improvement of GaInAsN on GaAs substrates for 1.3 μm laser emission

Metal organic vapor phase epitaxy (MOVPE) growth conditions for the preparation of GaInAsN/GaAs single quantum wells (SQW) have been investigated using tertiarybutylarsine (TBAs) and dimethylhydrazine (DMHy) as arsenic and nitrogen precursors, respectively. We found that a low reactor pressure is required to minimize the effect of the DMHy injection on the indium composition of GaInAsN alloys. We have also established that a high TBAs/III ratio results in a significant improvement of the crystal quality GaInAsN/GaAs SQWs when it is combined with a low growth rate and a low growth temperature. As a result of such optimisation, the photoluminescence (PL) intensity of SQWs emitting at 1.3 μm could be increased by one order of magnitude and the PL line width could be reduced by half compared with more standard conditions using a lower TBAs/III ratio. The lasing threshold of optimised GaInAsN lasers emitting at 1.24 μm could be reduced by a factor of 6. We achieved photoluminescence emission at wavelengths up to 1.35 μm and lasing at 1.26 μm with a threshold as low as 540 A/cm 2 for a cavity length of 1220 μm.

Heavy carbon doping of GaAs by MOVPE using a new dopant source CBrCl 3 and characterization of the epilayers

A new dopant source of carbon trichloro-bromide (CBrCl 3), an inter-substituted compound of two highly efficient dopants viz. CCl 4 and CBr 4, has been used for the heavy carbon doping of GaAs in metal organic vapor phase epitaxy (MOVPE) growth. High doping level of 1.12×10 20 cm −3 was achieved at growth temperature of 600°C and V/III ratio of 10. Self-compensation in the samples was systematically studied using the double crystal X-ray diffraction, Hall and photoluminescence measurements. Samples with hole concentration up to 7.36×10 19 cm −3 were free of compensation, while those with higher hole concentrations were found to be compensated. Compensations of the layers were calculated quantitatively from conventional lattice mismatch measurements. Anti-site incorporation of carbon was found to be the dominant compensation mechanism for hole concentration above 7.36×10 19 cm −3.

The addition of Sb as a surfactant to GaN growth by metal organic vapor phase epitaxy

The role and effect of the isoelectronic center Sb on the structure and properties of GaN epilayers have been investigated. The gas phase Sb concentration was varied by changing the triethyl antimony/trimethyl gallium mole ratio over a wide range of concentrations while keeping other growth parameters constant. The Sb addition slightly improved the optical and structural properties of GaN epilayer at a low level of Sb incorporation, especially for the films grown under a high group V/III ratio conditions. The addition of Sb resulted in changes in GaN surface morphology, which was further explored by the lateral epitaxy overgrowth (LEO) technique through the changes in the growth rates and the facet formation. The presence of Sb in the gas phase greatly enhanced the lateral overgrowth rate and altered the formation of the dominant facets. Vertical facets to the LEO growth appeared with the addition of Sb under conditions that normally produced sloped sidewalls. While Sb altered the growth facet present during LEO, only a small amount of Sb was incorporated into the GaN, suggesting that Sb acts as a surfactant during the GaN metal organic vapor phase epitaxy growth. Sb addition produces surface conditions characteristic of a Ga-rich surface stoichiometry indicating both a possible change in the reactivity of NH3 and/or enhanced surface diffusion of Ga adatom species in the presence of Sb.

A GaN-free LED Structure for High UV-light Extraction

ABSTRACTWe improved the extraction of ultraviolet light from AlGaN-based light emitting diodes (LEDs) at the wavelength of about 350 nm, by introducing a transparent structure that is free from binary GaN. We used an AlN-template layer on a sapphire substrate as starting medium of the metal organic vapor phase epitaxial growth. The buffer layer is an Al0.2Ga00.8N alloy. We also used a short period alloy superlattice as transparent and conductive p-type cladding and p-type contact layers. The resultant epitaxial structure is confirmed to be transparent with the transmittance of about 90% within the wavelength range of 340 – 400 nm. The crystal quality of the Al0.2Ga00.8N buffer layer was estimated by the transmission electron microscope (TEM) observation. The dislocation density of AlGaN buffer layer was highly reduced on the AlN template layer, both of which have a low density of screw and mixed-type dislocations, of the order of 10−8cm−2. We also found that light extraction is improved by a factor of 6 by introducing the transparent LED structure and a p-contact mirror. The resultant LED shows high performance under RT-CW operation, where 1 mW output power at 348 nm with 20 mA injection corresponds to the external quantum efficiency of 1.4 %. The maximum power was 7 mW at 220 mA. The emission spectrum is highly monochromatic with the UV-to-visible intensity ratio of about 1000. We also demonstrate the application of this transparent UV-LED to white light source in a bottom-emission geometry.

Initial stages of InP/GaP (100) and (111)A,B grown by metal organic chemical vapor deposition

The initial stages of the three-dimensional metal organic vapor phase epitaxy growth of InP/GaP (100) and (111)A,B were studied by atomic force microscopy (AFM) and Rutherford back scattering (RBS). We have shown that the heteroepitaxial growth takes place under Stranski–Krastanov mode (layer by layer and dislocation free island growth). By combining RBS and AFM results, we show that the wetting layer is about 0.51 and 0.4nm for (100) and (111)A,B orientated substrates, respectively. The critical thickness is found to depend on the substrate orientation. However, we show by the AFM technique that the shape, the height and the size of uncapped InP/GaP self-organized nanostructures depend on the amount of InP deposited and on the substrate orientation. In particular, the structure grown on (111)A,B substrate presents higher islands than the structure grown on (100). Therefore, the formation of nanostructures on substrates different from (100) is an interesting possibility to be investigated.

Natural formation of multiatomic steps on patterned vicinal substrates by MOVPE and application to GaAs QWR structures

In this paper, we investigate multiatomic steps naturally formed on patterned vicinal GaAs substrates during metal organic vapor phase epitaxial (MOVPE) growth. The substrates are (0 0 1)GaAs misoriented by 2.0° and 5.0° toward [−1 1 0] direction. Periodic trenches are formed on the substrate with periods of 0.4–4.0 μm along the [1 1 0] direction using electron beam lithography and wet etching techniques. Periodic multiatomic step structures are clearly observed on AlGaAs/GaAs grown surfaces which are almost equal to the periods of the underlying substrate patterns. From cross-sectional scanning electron microscope (SEM) images, the growth modes are observed. As the growth proceeds, the growth modes change and can be divided into three regions; the multiatomic step formation, transition and multiatomic step dissociation regions. The multiatomic step features also depend on the pattern periods. GaAs grown layer thicknesses at the edges of the multiatomic steps are thicker than those on the terraces, and this effect is prominent for shorter periodicity patterns. GaAs/AlGaAs quantum wells are grown on patterned vicinal substrates with a 0.4 μm period. The cathodoluminescence (CL) spectrum at 7.0 K has two emission peaks. From the surface and cross-sectional CL images, the lower energy peak corresponds to the quantum well formed at the edges of the multiatomic steps and the higher energy peak corresponds to that on the terrace, consistent with the results of cross-sectional SEM observations. Using optimized patterning and growth condition, we can fabricate highly uniform quantum wire (QWR) arrays at the step edges.

Growth model for GaN with comparison to structural, optical, and electrical properties

A kinetic model is presented to explain the metal organic vapor phase epitaxy (MOVPE) growth of GaN. The model is based upon measured desorption rates and assumptions on the precursor dissociation and sticking probabilities. The model shows how the growth temperature and V/III ratio are linked for the growth of high quality GaN films. From a comparison of growth conditions cited in the literature to the quality of GaN produced, optimal film growth appears to occur when the V/III ratio is chosen to be slightly larger than the N to Ga desorption ratio. The relationship between the growth temperature, V/III ratio, and GaN quality are explained in terms of how the growth parameters influence the incorporation of Ga and N atoms into the growing film. The Ga and N diffusion lengths are estimated to be 2–20 nm and &amp;lt;1 nm at 1050 °C, respectively, for practical MOVPE growth rates. Growth conditions for smooth (0001) surface morphology are described in terms of the growth model, as well as possible origins for defect incorporation in GaN. As a result of the large N desorption rate, it is suggested that during growth N is incorporated into the GaN lattice via an adsorption/desorption cycle. Application of the growth model to establishing the growth process conditions and run-to-run reproducibility are also discussed.

Metal organic vapor phase epitaxy growth of GaAsN on GaAs using dimethylhydrazine and tertiarybutylarsine

GaAsN layers with good structural quality and surface morphology have been successfully grown on a GaAs substrate using atmospheric pressure metal organic vapor phase epitaxy. A new combination of precursors namely, dimethylhydrazine for nitrogen and tertiarybutylarsine instead of conventional arsine for arsenic, greatly facilitated growths at temperatures as low as 500 °C. Layers with N content as high as 3% and corresponding to room temperature photoluminescence (PL) peak wavelength of 1.17 μm (1.064 eV) have been obtained.

Laser diodes integrated with butt-jointed spotsize converter fabricated on 2-in wafer

Laser diodes integrated with spotsize converters by butt-joint technology combined with selective area metal organic vapor phase epitaxial (MOVPE) growth have been successfully fabricated. Satisfactory uniformity, reproducibility (>99%) and tolerance for low threshold current, a narrow emitted beam, and low optical coupling loss to fiber (<-2.4 dB) are obtained by using 2-in full wafer fabrication technology in the experimental fabrication. To investigate the tolerance in fabrication, the characteristic dependence on the variation of the wet etching time just before the butt-joint MOVPE growth and also on the mesa stripe width are investigated. A wide tolerance for these fabrication parameters is confirmed. The results indicate that the butt-joint technology is a useful and reliable process for realizing spotsize converters of the present type and also suggest that the technology is widely applicable to various photonic integrated circuits.

InP/GaAs self-assembled nanostructures: Modelization and experiment

The initial stages of the three-dimensional metal organic vapor phase epitaxy growth of InP/GaAs have been studied by atomic force microscopy and Rutherford backscattering. The results are compared with the predictions of an equilibrium model that predicts an in-plane critical size for island formation. At low growth rates the model fits well the experiments while it needs to be further developed to include kinetic effects at higher growth rates. The experiments indicate a Stranski–Krastanow growth mode with a critical thickness of 2.1 ML.

Infra-red AlGaAs and visible AlGaInP laserdiode stack

A monolithic combination of an AlGaAs laser and an AlGaInP laser is demonstrated. The two lasers are grown in a stack, in a single metal organic vapour phase epitaxial growth. The two devices can be addressed individually, and exhibit good characteristics: for the AlGaAS laser, the pulsed threshold current density and efficiency are 240A/cm2 and 26%/facet, while the respective values for the red AlGaInP laser are 260A/cm2 and 21%/facet.

Electronic structure of short-period ZnSe/ZnTe superlattices grown by MOVPE at 300ºC

ABSTRACTThe ZnSe-ZnTe combination is a potential candidate for the realisation of visible light-emitting devices. The lattice mismatch between bulk ZnSe and bulk ZnTe is important (∼ 8%). Therefore, their hetero-structures are strained and high quality superlattices will only be grown if having small periods. This prescription can be fulfilled in the case of metal organic vapour phase epitaxy (MOVPE) growth by combining triethylamine dimethyl zinc adduct with di-isopropyl telluride as precursors for the growth of the ZnTe layers. The growth of high quality ZnTe can then be performed at a temperature of 300ºC , close to the best MOVPE-growth temperature for ZnSe (280ºC). Lowering the growth temperature of ZnTe to this value, we could thus obtain sharp interfaces. This work reports on ZnSe-ZnTe superlattices grown on ZnSe and ZnTe buffers deposited on GaAs substrates. We demonstrate that the stokes-shift between the reflectance and photoluminescence features ( ∼ 40 meV ) measured when the thickness of ZnSe layers does not exceed 20 Å, drastically increases for layer thicknesses beyond this critical value. This, we interpret in terms of the onset of plastic relaxation which favours tellurium diffusion in the ZnSe slices. Then photoluminescence spectra broaden ( contributions of trapped-excitons dominate), and observation of free excitons in reflectance become impossible. We have studied in detail the optical properties of the superlattices and compared our findings with the predictions of a multiband envelope function calculation. We show that both zone centre excitons as well as excitons associated with the miniband dispersions (saddle-point excitons) are observed in these superlattices.