GaAs Templates Research Articles

Investigation of OP-GaP Grown on OP-GaAs Templates Using Nondestructive Reciprocal Space Mapping

Orientation-patterned gallium phosphide (OP-GaP) has been grown heteroepitaxially on OP gallium arsenide (GaAs) templates using hydride vapor phase epitaxy (HVPE). The effect of OP-GaAs template fabrication methods of epitaxial-inversion and wafer bonding on the heteroepitaxial OP-GaP growth has been investigated. OP-GaP layers with a growth rate of up to 35 µm/h and excellent domain fidelity were obtained. The growth rate and the domain fidelity have been revealed/studied by scanning electron microscope (SEM). In addition, we demonstrate that the crystalline quality of the individual domains, namely, the substrate-oriented domains (ODs) and the inverted domains (IDs), can be investigated by high-resolution x-ray diffraction reciprocal space mapping (HRXRDRSM), which can also indicate the domain fidelity. Attempts to increase the growth rate and improve the domain fidelity by increasing the III and V group precursors resulted in either an increase in the growth rate in the OP-GaP layers grown on epitaxial inversion OP-GaAs template at the expense of the domain crystalline quality and fidelity or an improvement in the crystalline quality of the domains at the expense of the growth rate in the OP-GaP layers grown on wafer-bonded OP-GaAs templates. In the case of OP-GaP grown on OP-GaAs templates prepared by epitaxial inversion, the crystalline quality of the ODs is better than that of the IDs, but it shows that the quality of the inverted layer in the template influences the quality and fidelity of the grown domains. To the authors’ knowledge, exploitation of HRXRDRSM studies on OP-GaP to establish the crystalline quality of its individual domains (ODs and IDs) is the first of its kind. OP-ZnSe grown on OP-GaAs templates has also been included in this study to further emphasize the potential of this method. We propose from this study that once the growth rate is optimized from SEM studies, HRXRDRSM analysis alone can be used to assess the structural quality and to infer the domain fidelity of the OP structures.

Second‐Harmonic Generation in Heteroepitaxially Grown, Orientation‐Patterned, Ternary GaAsP Periodic Structures

Orientation‐patterned GaAs0.85P0.15 is grown by hydride vapor phase heteroepitaxy on an orientation‐patterned GaAs template and second‐harmonic generation is demonstrated for this ternary periodic structure using ultrashort pulses with an internal conversion efficiency exceeding 19%.

Molecular beam epitaxy of GaAs templates on water soluble NaCl thin films

Expensive III-V substrates are cost limiting for the adoption of many technologies. Thus, being able to reuse the original substrate is highly desirable. Existing substrate reuse techniques have significant drawbacks, but this work discusses a new method using molecular beam epitaxy deposition of water soluble NaCl thin films on commonly employed (001) GaAs substrates. Single-crystal GaAs templates are grown on continuous NaCl layers utilizing careful exposure of the NaCl to an in-situ electron beam and a low temperature nucleation layer. The template layers can be quickly removed from the substrate via dissolution of the NaCl. After liftoff, the original wafer shows an increase in rms surface roughness of only 0.2 nm.

An electrically driven whispering gallery polariton microlaser.

Near-infrared micro/nanolaser devices utilizing low-dimensional semiconductors can provide essential building blocks to achieve integrated optoelectronic devices and circuitry for advanced functionalities and are compatible with on-chip technologies. Although significant progress has been made through using narrow-band semiconductor micro/nanostructures to realize near-infrared stimulated radiation at room temperature, severe challenges still remain involving much lower quantum efficiencies and higher auger recombination. Herein, we report an experimental realization of a current-injection semiconductor polariton device made of a ZnO microwire via Ga-doping (ZnO:Ga MW) and p-type GaAs template. The device can emit polaritonic illumination directly from sharp edges of the hexagonal MW. The experimental results of angle-resolved electroluminescence measurements reveal a typical anticrossing feature between excitons and cavity modes, unambiguous evidence of the strong exciton-polariton coupling, with corresponding Rabi splitting energy extracted to be about 195 meV. As the applied bias goes above a certain value, electrically driven whispering gallery lasing action was achieved in the near-infrared spectrum, and the lasing features can be assigned to the exciton-polariton effect. The results not only can afford insights into the development of low-threshold coherent light sources via the exciton-polariton effect, but also can expand the fabrication of low-dimensional, near-infrared microlaser devices.

Thick Heteroepitaxy of Binary and Ternary Semiconductor Materials for Nonlinear Frequency Conversion in the Mid and Longwave Infrared Region

Thick hydride vapor phase heteroepitaxy of some III–V, II–VI, and III–VI binary and ternary semiconductor materials such as GaAs, GaP, GaP, GaAsxP1‐x, ZnSe, and GaSe is performed on GaAs substrates and orientation‐patterned GaAs templates. Up to 500 μm thick GaAs, GaP, GaP, GaAsxP1‐x, and ZnSe layers are deposited in single growths or after a regrowth. The GaSe layers deposited through van der Waals heteroepitaxy are up to 4–5 μm thick. When possible, growths are also performed homoepitaxially as the comparison of growth rate and layer quality indicates similar or better results in some of the heteroepitaxial cases. Material analysis using optical microscopy, scanning electron microscopy, atomic force microscopy, high‐resolution X‐ray diffraction, and energy dispersive X‐ray spectroscopy indicate smooth surface morphology, uniform layer thicknesses, high crystalline quality, and gradual substrate‐to‐layer material transition in the cases of heteroepitaxy. Respectively, the growths on the templates prepared by an optimized polarity inversion technique (assisted by molecular‐beam epitaxy) reveal excellent domain fidelity and good infrared transparency. The samples grown on templates are intended for frequency conversion devices operating in mid and longwave infrared. The layers grown on plain substrates are meant to support applications in optoelectronics, renewable energy, sensing, and solar cells.

Heteroepitaxial growth of nonlinear optical materials for frequency conversion in the mid and longwave IR

We report recent results on heteroepitaxy of ZnSe on GaAs, GaSe on GaP, GaAs and GaN substrates, and GaAsxP1−x ternaries on GaAs, as well growths of OPGaP, OPGaAsP and OPZnSe on orientation-patterned (OP) GaAs templates. ZnSe and GaSe were chosen for their wide IR transparency and good NLO properties, taking advantages from the close lattice match of ZnSe to GaAs, α–Ga4Se6 (cubic) to GaP and GaAs, and β–GaSe (hexagonal) to GaN. For the same reason growth of OPGaP was attempted on OPGaAs templates. As for the GaAsxP1−x ternaries, the idea was to determine whether these ternaries can combine in one material the lower 2-photon absorption of GaP with the higher nonlinear susceptibility of GaAs since a GaAsxP1−x ternary always has a closer lattice match to either GaAs or GaP than the two parenting materials. Up to 500 µm thick layers grown by Hydride Vapor Phase Epitaxy (HVPE) on plain substrates and up to 300 µm thick OP structures grown on OP templates revealed smooth surface morphology (RMS < 2 nm from 1 μm2 AFM scan) and superior crystalline quality (FWHM < 100 arcsec of the XRD Omega scan). The growth of α–GaSe/GaAs can be considered as a low-dimensional Van-der-Waals heteroepitaxy. Further characterization of the heteroepitaxial layers by Nomarski optical imaging, linear transmission and nonlinear absorption measurements, TEM, SEM, AFM, and EDX revealed that in some of the cases a smooth transition between the substrate and the layer material can be achieved by the formation at the interface of an intermediate ternary layer with a gradually changing composition. It also indicated that during fast growth processes, such as HVPE, the strain built due to the lattice and the thermal mismatch between substrate and growing layer shall be relaxed in faster and more energy absorbing processes such as formation of voids or roughening surfaces (GaP/GaAs) or an immediate formation of stacking faults that originate still from the substrate (ZnSe/GaAs). All this may postpone or even replace the formation of the expected misfit dislocations frequently observed in the slower MOCVD and MBE growths.

Achieving wavelength emission beyond the C-band from Type-II InAs-GaAsSb quantum dots grown monolithically on silicon substrate

Abstract The optical quality enhancement of a GaAs template grown on Silicon substrate using InGaAs/GaAs Dislocation Filters (DFs) combined with an annealing step have been assessed optically using Photoluminescence (PL) of embedded InAs/InGaAs QDs within a GaAs matrix. An annealing temperature after the growth of the DFs of 690 °C was shown to be optimum, giving an enhanced PL emission from the embedded InAs QDs in terms of intensity and Full Width at Half Maximum (FWHM). InAs quantum dots capped with GaAsSb grown at different temperatures were grown on the optimized GaAs template on Si. The prepared samples were characterized by PL, Atomic Force Microscopy (AFM), excitation power and dependent PL at 77 K and 300 K. At 77 K, the InAs/GaAsSb grown at 484 °C showed a type II band alignment with an emission wavelength of 1297 nm, which is shorter than the emission obtained from the reference sample, where the GaAsSb-capped dots were grown on GaAs (1357 nm). By reducing the GaAsSb capping layer growth temperatures to 465 °C and 450 °C, the wavelength at 77 K was extended to 1375 nm and 1480 nm respectively, resulting from an increased Sb content in the capping layer. At 300 K, a long wavelength emission of 1623 nm have been achieved.

Heteroepitaxy of orientation-patterned nonlinear optical materials

We report some recent results on thick heteroepitaxial growth of GaP on GaAs substrates and on orientation-patterned (OP) GaAs templates conducted in a hot-wall horizontal quartz reactor for Hydride Vapor Phase Epitaxy. The growths on the plain substrates resulted in up to 500 µm thick GaP with smooth surface morphology (RMS < 1–2 nm) and high crystalline quality (FWHM = 100–150 arcsec), comparable to the quality of the related homoepitaxial growths of GaP on GaP. Up to 300 µm thick OPGaP quasi-phase matching structures with excellent domain fidelity were also heteroepitaxially grown with high reproducibility on OPGaAs templates in support of frequency conversion laser source development for the mid and longwave infrared. We studied the GaAsxP1−x ternary transition layer that forms between the growing film and the substrate. We also undertook steps to determine some important characteristics of heteroepitaxy such as thickness of the pseudomorphous growth and periodicity of the expected misfit dislocations. The formation of these and some other defects and their distribution within the layer thickness was also investigated. Samples were characterized by Nomarski optical microscopy, transmission optical measurements, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The focus was predominantly on the interface and, more precisely, on what influence the pre-growth surface treatment of the substrate has on the initial and the following stages of growth, as well on the mechanisms of the strain relaxation from the lattice and thermal mismatch between layer and substrate. The efforts to accommodate the growing film to the foreign substrate by engineering an intermediate buffer layer were extended to thick growths of GaAsxP1−x ternary with the idea to combine in one material the best of the nonlinear properties of GaP and GaAs that are strictly relevant to the pursued applications.

Low threading dislocation density GaAs growth on on-axis GaP/Si (001)

We report a systematic study of high quality GaAs growths on on-axis (001) GaP/Si substrates using molecular beam epitaxy. Various types of dislocation filter layers and growth temperatures of initial GaAs layer were investigated to reduce the threading dislocation densities in GaAs on GaP/Si. Electron channeling contrast imaging techniques revealed that an optimized GaAs buffer layer with thermal cycle annealing and InGaAs/GaAs dislocation filter layers has a threading dislocation density of 7.2 × 106 cm−2, which is a factor of 40 lower than an unoptimized GaAs buffer. The root-mean-square surface roughness was greatly decreased from 7.8 nm to 2.9 nm after the optimization process. A strong enhancement in photoluminescence intensity indicates that the optimized GaAs template grown on on-axis (001) GaP/Si substrates is a promising virtual substrate for Si-based optoelectronic devices.

High efficiency low threshold current 1.3 μm InAs quantum dot lasers on on-axis (001) GaP/Si

We demonstrate highly efficient, low threshold InAs quantum dot lasers epitaxially grown on on-axis (001) GaP/Si substrates using molecular beam epitaxy. Electron channeling contrast imaging measurements show a threading dislocation density of 7.3 × 106 cm−2 from an optimized GaAs template grown on GaP/Si. The high-quality GaAs templates enable as-cleaved quantum dot lasers to achieve a room-temperature continuous-wave (CW) threshold current of 9.5 mA, a threshold current density as low as 132 A/cm2, a single-side output power of 175 mW, and a wall-plug-efficiency of 38.4% at room temperature. As-cleaved QD lasers show ground-state CW lasing up to 80 °C. The application of a 95% high-reflectivity coating on one laser facet results in a CW threshold current of 6.7 mA, which is a record-low value for any kind of Fabry-Perot laser grown on Si.

Thick orientation-patterned growth of GaP on wafer-fused GaAs templates by hydride vapor phase epitaxy for frequency conversion

Quasi-phase-matched (QPM) GaP layers up to 300 μm thick have been produced by low-pressure hydride vapor phase epitaxy (LP-HVPE) overgrowth on orientation-patterned GaAs (OPGaAs) templates fabricated using a wafer-fusion bonding technique. The growth on the OPGaAs templates resulted in up to 200 μm thick vertically propagating domains, with a total GaP thickness of 300 μm. The successful thick growth on OPGaAs templates is the first step towards solving the material problems associated with unreliable material quality of commercially available GaP wafers and making the whole process of designing QPM frequency conversion devices molecular beam epitaxy free and more cost-effective.

Electrical switching of photoluminescence of single site‐controlled InAs quantum dots

Voltage-controlled photoluminescence (PL) switching is demonstrated for single site-controlled InAs quantum dots (QDs) embedded in Schottky–i–n diodes grown by molecular beam epitaxy on nanoimprint lithography patterned GaAs templates. The PL emission was quenched by applying a voltage over the diode structure due to the increased tunnelling rate of charge carriers out of the QDs.

Controlled nucleation and optical properties of InAs quantum dots grown on faceted GaAs microstructures

AbstractWe present a study of the site‐controlled nucleation of InAs quantum dots on faceted GaAs microstructures grown by migration enhanced epitaxy and demonstrate single quantum dot emission. Well defined GaAs templates with facets mostly belonging to the crystal plane families {01n }, {11n } and (001) are realized. Subsequent InAs nucleation occurs on the plane with the highest growth rate, and allows a precise positioning of optical active InAs quantum dots. The site‐controlled quantum dots reveal excitonic and biexcitonic transitions with narrow linewidths. The results are promising for the realization of single photon sources from site‐selected InAs QDs on faceted GaAs microstructures. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

In-rich molecular beam epitaxy of InAs on Sb-terminated GaAs(001) surface

The effect of various Sb-terminated GaAs(001) templates on the growth of InAs was investigated by varying the As flux. The growth of InAs under In-rich growth conditions on Sb-terminated GaAs(001)-(2×3), (2×4) and (2×8) templates was demonstrated to occur in the Stranski-Krastanov (SK) growth mode, in contrast to the Sb-free case, where the growth process follows the Franck-van der Merwe (FM) growth mechanism. The observed antimony dependent change of growth mode from FM to SK is qualitatively explained by the decrease of the surface energy of the growing InAs layer caused by the segregation of Sb on the surface of the InAs(001).

Nanoimprint and selective-area MOVPE for growth of GaAs/InAs core/shell nanowires

We report on the technology and growth optimization of GaAs/InAs core/shell nanowires. The GaAs nanowire cores were grown selectively by metal organic vapor phase epitaxy (SA-MOVPE) on SiO2 masked GaAs templates. These were structured by a complete thermal nanoimprint lithography process, which is presented in detail. The influence of the subsequent InAs shell growth temperature on the shell morphology and crystal structure was investigated by scanning and transmission electron microscopy in order to obtain the desired homogeneous and uniform InAs overgrowth. At the optimal growth temperature, the InAs shell adopted the morphology and crystal structure of the underlying GaAs core and was perfectly uniform.

Structural, morphological, and magnetic characterization of In1−xMnxAs quantum dots grown by molecular beam epitaxy

In this paper, we present a method to order low temperature (LT) self-assembled ferromagnetic In1−xMnxAs quantum dots (QDs) grown by molecular beam epitaxy (MBE). The ordered In1−xMnxAs QDs were grown on top of a non-magnetic In0.4Ga0.6As/GaAs(100) QDs multi-layered structure. The modulation of the chemical potential, due to the stacking, provides a nucleation center for the LT In1−xMnxAs QDs. For particular conditions, such as surface morphology and growth conditions, the In1−xMnxAs QDs align along lines like chains. This work also reports the characterization of QDs grown on plain GaAs(100) substrates, as well as of the ordered structures, as function of Mn content and growth temperature. The substitutional Mn incorporation in the InAs lattice and the conditions for obtaining coherent and incoherent structures are discussed from comparison between Raman spectroscopy and x-ray analysis. Ferromagnetic behavior was observed for all structures at 2 K. We found that the magnetic moment axis changes from [110] in In1−xMnxAs over GaAs to [1-10] for the ordered In1−xMnxAs grown over GaAs template.

The influence of temperature on the photoluminescence properties of single InAs quantum dots grown on patterned GaAs

We report the temperature-dependent photoluminescence of single site-controlled and self-assembled InAs quantum dots. We have used nanoimprint lithography for patterning GaAs(100) templates and molecular beam epitaxy for quantum dot deposition. We show that the influence of the temperature on the photoluminescence properties is similar for quantum dots on etched nanopatterns and randomly positioned quantum dots on planar surfaces. The photoluminescence properties indicate that the prepatterning does not degrade the radiative recombination rate for the site-controlled quantum dots.

Demonstration of Single Crystal GaAs Layers on CTE-Matched Substrates by the Smart Cut Technology

Templates made of a thin single crystal GaAs layer on CTE-matched substrate (sapphire) have been realized using the Smart CutTM technology. These templates can withstand high processing temperatures thanks to the CTE matching between the GaAs thin film and its support, and therefore can be used for many applications since they require no specific restriction concerning thermal treatments. The GaAs templates have been compared to conventional bulk GaAs substrates. TEM images and XRD spectra show similar crystalline quality. AFM measurements show a similar surface microroughness. Photoluminescence of a AlGaAs double heterostructure grown by MOCVD on the GaAs template shows the same intensity as a reference structure on bulk GaAs. Therefore, the GaAs templates can replace GaAs bulk substrates in various domains such as photonics devices (solar cell, laser) or high frequency electronics.

Large array of single, site-controlled InAs quantum dots fabricated by UV-nanoimprint lithography and molecular beam epitaxy

We present the growth of single, site-controlled InAs quantum dots on GaAs templates using UV-nanoimprint lithography and molecular beam epitaxy. A large quantum dot array with a period of 1.5 µm was achieved. Single quantum dots were studied by steady-state and time-resolved micro-photoluminescence experiments. We obtained single exciton emission with a linewidth of 45 µeV. In time-resolved experiments, we observed decay times of about 670 ps. Our results underline the potential of nanoimprint lithography and molecular beam epitaxy to create large-scale, single quantum dot arrays.

Interface magnetism of iron grown on sulfur and hydrogen passivated GaAs(001)

Sulfur (S) and hydrogen (H) atom passivated GaAs(001) templates were used for deposition of ultrathin crystalline Fe films using molecular beam epitaxy, where the Fe thickness ranged from 10 to 45 atomic layers. Reflection high-energy electron diffraction patterns showed that the S- and H-passivated surfaces had no and very weak (1 × 2) superlattice reconstructions, respectively. This indicates that these GaAs(001) templates have a square-like symmetry. Magnetic anisotropies were investigated using the in-plane angular dependence of ferromagnetic resonance at 36 GHz. The in-plane cubic and uniaxial anisotropies and perpendicular uniaxial field were described by bulk and interface contributions, indicating that the Fe films have a high lattice coherence. The magnetic properties of the Fe films were compared to those grown on more commonly used GaAs(001) templates having a (4 × 6) reconstruction with an As-rich in-plane uniaxial symmetry. The Fe films grown on S-passivated templates exhibited unique magnetic properties caused by a decreased lattice spacing compared to the bulk Fe.