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Selective area epitaxy (SAE) can be used to grow highly uniform III–V nanostructure arrays in a fully controllable way and is thus of great interest in both basic science and device applications. Here, an overview of this promising technique is presented, focusing on the growth fundamentals, formation of III–V nanowire arrays, monolithic integration of III–V nanowire arrays on silicon, the growth of nanowire heterostructures, and networks of various shapes. The applications of these III–V nanostructure arrays in photonics, electronics, optoelectronics, and quantum science are also reviewed. Finally, the current challenges and opportunities provided by SAE are discussed.

Vertical InAs nanowires (NWs) grown on a Si substrate are promising building-blocks for next generation vertical gate-all-around transistor fabrication. We investigate the initial stage of InAs NW selective area epitaxy (SAE) on a patterned Si (111) substrate with a focus on the interfacial structures. The direct epitaxy of InAs NWs on a clean Si (111) surface is found to be challenging. The yield of vertical InAs NWs is low, as the SAE is accompanied by high proportions of empty holes, inclined NWs, and irregular blocks. In contrast, it is improved when the NW contains gallium, and the yield of vertical InxGa1-xAs NWs increased with higher Ga content. Meanwhile, unintentional Ga surface contamination on a patterned Si substrate induces high yield vertical InAs NW SAE, which is attributed to a GaAs-like seeding layer formed at the InAs/Si interface. The role of Ga played in the III-V NW nucleation on Si is further discussed. It stabilizes the B-polarity on a non-polar Si (111) surface and enhances the nuc...

We describe an x-ray microprobe measurement of selectively grown heteroepitaxial Si1−xGex on Si. The experiment was conducted at the European Synchrotron Radiation Facility of Grenoble at the ID13 Microfocus beamline. The Si1−xGex layers were deposited by a standard chemical vapor deposition process on patterned 200 mm wafers of monocrystalline Si substrate. The uniformity of the pseudomorphic layers, in terms of Ge content and thickness, is evaluated by double crystal x-ray diffraction with the use of a novel microgoniometer and with a spatial resolution of ∼5×7.5 μm2. The results show the good uniformity of the SiGe layers and indicate the possibility of evaluating the strain fields near the shallow trench isolation structures.

We describe the growth and characteristics of AlInGaAs, self-aligned buried heterostructure quantum well lasers deposited by micro-selective-area growth. The lateral waveguide is defined by metalorganic vapor-phase epitaxy in narrow stripe openings; and the natural tendency to form smooth, no-growth {111} sidewall planes produces a low-loss, single-mode waveguide. By proper adjustment of the growth conditions after the waveguide formation, the waveguide may be buried in p-type InP. A buried heterostructure (BH) laser is there formed in a single growth step, eliminating the deterioration associated with air exposure and etch damage, especially for AlInGaAs active regions. The AlInGaAs BH lasers formed in this simple manner exhibit good performance characteristics, with room-temperature threshold current of 4mA.

The surface of strained InGaAs films for selective regrowth of InAs nanostructures is investigated by atomic force microscopy and Rutherford backscattering. 3.3-nm-thick In0.33Ga0.67As films were annealed at temperatures between 400 and 800 °C. Significant indium desorption was found to occur at temperatures above 550 °C. The optimum parameters are presented for selective growth of InAs quantum dots having densities of 6.6×1010 cm−2 on In0.33Ga0.67As films.

We report the growth and characterization of patterned ZnCdSe/ZnCdMgSe quantum-well (QW) structures grown adjacent to each other on a single InP substrate. Each structure emits at a different wavelength range spanning the visible range. Stripe and square-shaped QW structures of different emission wavelengths, with lateral dimensions between 15 and 60 μm, were deposited sequentially by shadow mask selective area epitaxy (SAE) steps. Conventional and microphotoluminescence measurements were used to characterize the patterned QWs. They exhibit well-defined excitonic emission in the red, yellow, and green regions of the visible spectrum. This result demonstrates the feasibility of fabricating integrated full-color light emitting diode and laser-based display elements and white light sources using the ZnCdMgSe material system and shadow mask SAE.

GaN grown by selective area epitaxy and subsequent lateral overgrowth exhibits sharply peaked anisotropic structures in the form of hexagonal pyramids and ridges. Spatially resolved optical emission from these structures, using both cathodoluminescence and collection-mode near-field scanning optical microscopy, of radiation centered near 550 nm, the so-called yellow band, indicates that the emission arises predominantly from the apex regions of the pyramids and ridges. In contrast, transmission electron microscopy shows that the apex region is nearly dislocation free and that dislocations cluster at the vertical growth core region. The spatial separation of the dislocations and optical emission indicates that the yellow-band emission has no direct relationship to dislocations. The observation of yellow-band emission strongly localized in the apical regions of both types of structures and the tendency of impurity species to concentrate in these areas argues that it arises instead from impurity states, the ...

The selective area epitaxy of GaInAs/InP layers grown by low‐pressure metalorganic vapor phase epitaxy through SiO2 patterned masks was investigated. The layers are found to develop mesa structures limited by {111} and (100) facets outside of the opened mask, and perfect selective epitaxy is obtained. The absence of GaInAs growth on {111} facets allows the fabrication of very narrow buried GaInAs layers in a single growth step. For both materials, the growth rates are found to depend strongly on the mask geometry owing to surface diffusion of the reactant species from the no‐ or low‐growth SiO2 mask and {111} facets toward (100) surfaces. A detailed quantitative analysis is made to identify the critical parameters that control the growth behavior, and a model is described from which the upper limit of the growth rates for any mask design can be calculated. Low‐temperature cathodoluminescence measurements show strong emission of the buried GaxIn1−xAs layers and indicate local stoichiometry variations Δx≂±5...

Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. The model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. The model provides a route to optimize masks and processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.

Nanowires (NWs) grown via selective area epitaxy (SAE) show great promise for applications in next generation electronic and photonic devices, yet the design of NW-based devices can be complicated due to the complex kinetics involved in the growth process. The presence of the patterned selective area mask, as well as the changing geometry of the NWs themselves during growth, leads to non-linear growth rates which can vary significantly based on location in the mask and the NW size. Here, we present a systematic study of the evolution of GaAs NW geometry during growth as a function of NW size and pitch. We highlight a breakdown of NW uniformity at extended growth times, which is accelerated for NW arrays with larger separations. This work is intended to outline potential fundamental growth challenges in achieving desired III–V NW array patterns and uniformity via SAE.

We have studied the selective formation of InAs self-organized quantum dots on top of [001]- and [011]-oriented mesa stripes on patterned GaAs (100) substrates. The GaAs stripes are also grown by selective area epitaxy. The dot density and spatial distribution depend on both the stripe orientation and the width of the (100) top facet of the stripe. The density is higher for stripes aligned in the [001] direction, and lower for those aligned in the [011] direction, respectively, when compared to that obtained on a planar substrate under the same growth conditions. In addition, the dot uniformity is improved by reducing the top facet width below 200 nm in the growth of the mesa stripes, and well-aligned rows of dots are obtained for sub-100-nm widths.

Epitaxial lateral mask overgrowth which occurs during GaN selective epitaxy has been studied using linear mask features. The lateral growth varies between its maximum and minimum over a 30° angular span and exhibits hexagonal symmetry. Vertical growth follows an opposite trend, with lateral growth maxima, and vertical growth minima occurring for lines parallel to the GaN 〈10•0〉. Large variations in the lateral growth are also obtained through variations in the growth temperature and NH3 flow. Under proper growth conditions, lateral to vertical growth rate ratios of up to 4.1 can be achieved, resulting in significant lateral mask overgrowth and coalescence of features without excessive growth times.

GaInAs layers were grown selectively on partially masked InP substrates by metalorganic vapor phase epitaxy using the conventional In precursor trimethyl‐indium (TMI) and the intramolecularly saturated compound dimethylaminopropyl‐dimethyl‐indium (DADI) for comparison. We obtained for both TMI and DADI an excellent morphology of the selectively grown structures. Significant differences between the two In sources were determined for the unwanted nucleation on the masked area and for the homogeneity of the composition of the grown ternary material. We attribute this observation to the higher chemical stability of DADI and a changed decomposition behavior, which leads to longer effective diffusion lengths for DADI and its thermally decomposed fragments in the gas phase.

Using scanning force microscopy we have studied the growth rate enhancement at the edge of InP and lattice matched InGaAs layers grown into openings on SiO2‐masked InP substrates by selective area epitaxy. The growth method was metalorganic molecular beam epitaxy. The growth rates were measured at the center and at the edge of the openings using a scanning force microscope. We have found that the growth rate enhancement can be minimized by using lower metalorganic and hydride flows, and that diffusion is the dominant process at work in the formation of the edge. The migration length of the species depends on the arrival rate of the precursor molecules to the substrate, determined by the absolute group III and V flows, and not on the nominal V/III ratio used for the growth.

A method is presented for maximizing the yield and crystal phase purity of vertically aligned Au-assisted GaAs nanowires grown with an SiOx selective area epitaxy mask on GaAs (111)B substrates. The nanowires were grown by the vapor-liquid-solid (VLS) method in a gas source molecular beam epitaxy system. During annealing, Au VLS seeds will alloy with the underlying GaAs substrate and collect beneath the SiOx mask layer. This behavior is detrimental to obtaining vertically aligned, epitaxial nanowire growth. To circumvent this issue, Au droplets were pre-filled with Ga assuring vertical yields in excess of 99%.

We demonstrate the use of an ultrathin (≊5 nm) Si layer deposited on InP substrates as a mask in selective area epitaxy of InGaAs by metalorganic molecular beam epitaxy. Patterns of varying shapes and sizes, from 5 to 0.5 μm, were written on the mask by focused Ga ion beam and etched by Cl2. The growth rate of InGaAs was studied by scanning force microscopy using stripes with guard rings spaced as close as 0.5 μm from the stripes. A small increase in the growth rate was detected only when the feature size was lower than 5 μm, and the growth rate was not affected by the presence of the guard rings. This shows that precursor material is being transferred from the slow growing {111}‐planes to the (100)‐plane, and that migration of species from the Si mask to the growing areas is negligible.

Heterostructure bipolar transistors (HBT) have been grown by selective area epitaxy (SAE) using metalorganic molecular beam epitaxy (MOMBE). dc characteristics, comparable to those for devices grown on unprocessed substrates, were obtained after removal of the edge growth. Data is also presented for devices in which the emitter mesas were regrown by SAE into openings which had been previously defined by photolithography on a structure containing only the collector and base layers. In both cases we use an in situ cleaning process consisting of an Ar ion beam sputtering and Cl2 etching. This step results in significantly improved junction quality.

Photoassisted heteroepitaxy of ZnSe on GaAs by metalorganic molecular beam epitaxy has been performed using sources of diethylselenium and diethylzinc. Illuminating the substrate during growth with an Ar ion laser has been observed to significantly enhance the growth rate. Growth rate enhancement was found to be a function of substrate temperature, VI/II gas flow ratio, and laser wavelength and intensity. Photons having energies sufficient to generate electron/hole pairs in the growing ZnSe film resulted in growth rate enhancement. The photoassisted growth has application for (i) increasing the anomalously low growth rate which is observed, (ii) assisting in tuning the surface stoichiometry, and (iii) providing for selective area epitaxy.

We report for the first time the successful selective deposition and fabrication of a silicon‐doped GaAs metal‐semiconductor‐field‐effect transistor by laser‐assisted chemical vapor deposition. No measurable growth or conductance outside the laser‐irradiated area was observed, indicating complete selectivity was achieved. The Schottky gate contact showed an ideality factor of 1.15 and the reverse breakdown voltage is about 38 V at a leakage current density of 1 μA/(μm)2. The current saturation beyond pinch‐off is fairly flat, indicating a good buffer layer and interfaces.

Laser‐assisted chemical vapor deposition offers a new approach for the integration of optoelectronic devices. We report for the first time the selective deposition and fabrication of a GaAs p‐i‐n photodetector. The detector, fabricated on a 200×200 μm mesa, shows an impulse response with a full width at half maximum of 150 ps and external quantum efficiency (no AR coating) of 60% both at 0 and −1.4 V bias. These results show that the p‐i‐n detector has a performance comparable to that achieved by metalorganic chemical vapor deposition and molecular beam epitaxy for similar device dimensions.

We report on the properties of green light-emitting diodes (LEDs) with a photonic crystal (PC) structure on p-GaN. A PC structure was fabricated by the selective area epitaxy of p-GaN using SiO2 nanopillars. The electrical characteristics of LEDs with PC were not degraded and the optical output power of green LEDs with PC was increased by 70% at 20 mA of injection current compared with that of conventional LEDs without PC. This enhancement of optical output power was attributed to the improvement in light extraction efficiency by the SiO2/p-GaN PC layer on p-GaN.

InGaN quantum well (QW) microrings were grown using selective area epitaxy on patterned (0001) AlN/sapphire. The well defined shapes are comprised of {112¯2} and {213¯3} facets on inner sidewalls, and {11¯01} facets on outer sidewalls, as well as (0001) top surfaces. The sidewall facets exhibit distinct emission spectra when investigated using cathodoluminescence. Differences in emission spectra are attributed to variations in growth rate and indium incorporation on the facets, with peak emission wavelength as long as 500 nm. The observed weak blueshift with increasing cathodoluminescence excitation current verifies that the internal piezoelectric fields of the semipolar sidewall facets are lower than reference (0001) InGaN QWs.

Selective area epitaxy has been used to grow pyramidal GaN stripes, followed by InGaN multiple quantum well (MQW) structures, in order to produce long-wavelength green light emission. Stripes oriented along ⟨112¯0⟩ produce smooth {11¯01} sidewall facets. The room-temperature optical properties are investigated by cathodoluminescence spectroscopy using a scanning electron microscope. MQWs grown in unmasked reference regions exhibit emission at 450 nm. The stripe sidewalls emit light with peak wavelength of 500 nm with consistent linewidth and intensity. The stripe ridge emits light with peak intensity at wavelength of ∼550 nm. Based on the spatial extent of the 550 nm emission, the ridge is estimated to be ∼250 nm wide. The large redshift is produced by the enhanced presence of indium species due to lateral vapor diffusion and surface migration in selective area epitaxy.

Metal-organic chemical vapor deposition has been used for selective epitaxy of GaN pyramids ranging in size from over 1μm to 500 nm in length at the base. Pyramids are terminated by {11¯01} crystal facets. The optical properties of the pyramids are investigated by cathodoluminescence (CL) in a scanning electron microscope. CL spectrum imaging reveals the pyramid apices to emit light at ∼363.4 nm corresponding to the emission wavelength of relaxed GaN. As the CL excitation is moved away from the apex a systematic redshift is observed. The redshift is ∼4 nm for pyramids with 3 μm base dimension and ∼2 nm for the 500 nm pyramids. The shift is attributed to diffusion of silicon and oxygen into the GaN pyramids due to SiO2 mask decomposition with negligible contribution from stress. The observations are backed by finite element simulations of diffusion and stress.

Semipolar InGaN∕GaN multiple quantum wells (MQWs) were fabricated on the {101¯1} facets of GaN pyramidal structures by selective area epitaxy. Optical properties of the MQWs were investigated by photoluminescence (PL) in comparison with (0001) MQWs. Compared with (0001) MQWs, the internal electric field in the {101¯1} MQWs was remarkably reduced, the PL peak redshifted monotonically with the increasing temperature, and the internal quantum efficiency was estimated to be improved by a factor of 3. These results suggest that the {101¯1} planes are promising for improving the performance of III-nitride light emitters owing to their surface stability and suppression of polarization effects.

We analyze temperature-dependent photoluminescence (PL) behavior of patterned InAs∕GaAs quantum dots (PQDs) formed by selective area epitaxy using metalorganic chemical vapor deposition. The processing scheme, described here, yields an ensemble of electronically isolated PQDs with PL characteristics that significantly differ from self-assembled (SA) QDs since neither a wetting layer nor neighboring QDs are available for coupling. The isolated nature of the PQDs supports a non-Fermi (nonequilibrium) carrier distribution which yields very different PL characteristics compared to the Fermi (equilibrium) distribution of the SAQDs especially at temperatures >100K. Thus, the PQDs demonstrate a constant PL linewidth within the temperature range of 80–300K along with improved temperature stability of PL intensity in comparison to SAQDs. The increased temperature stability allowed by electronic isolation may prove very important for high speed, temperature-insensitive QD laser development.

An integrated process to fabricate controllable arrays of semiconductor nanorings and nanodots on patterned surfaces is presented. This approach is based on pattern transfer of nanopores to a SiO2 layer, followed by selective epitaxial growth of InGaN onto an underlying GaN substrate using metalorganic chemical vapor deposition. Using this approach, crystalline InGaN nanorings and nanodots ∼80nm in diameter have been grown on GaN surfaces. The formation mechanism of the nanorings and nanodots is described based on the initial stage of selective growth and restricted atom migration in a confined hole. Strong photoluminescence obtained at room temperature from the noncapped nanorings indicates strong confinement of the excitons in the nanostructures. This approach enables fabrication of dense, uniform arrays of epitaxial nanostructures and is potentially applicable to a variety of materials systems.

Selective growth of InGaAs quantum dots on GaAs is reported. It is demonstrated that selective-area epitaxy can be used for in-plane bandgap energy control of quantum dots. Atomic force microscopy and cathodoluminescence are used for characterization of the selectively grown dots. Our results show that the composition, size, and uniformity of dots are determined by the dimensions of the mask used for patterning the substrate. Properties of dots can be selectively tuned by varying the mask dimensions. A single-step growth of a thin InGaAs quantum well and InGaAs quantum dots on the same wafer is demonstrated. By using a single-step growth, dots luminescing at different wavelengths, in the range 1150-1230 nm, in different parts of the same wafer are achieved. © 2005 American Institute of Physics.

The use of thermal oxides of Al(x)Ga(1-x)As (x = 0-1) as masking materials for selective-area epitaxy by a organometallic chemical-vapor deposition has been investigated. It was found that the thermal oxide of GaAs is only applicable for low growth temperatures (less than or equal to 600 C), and the addition of aluminum significantly improves the thermal stability of the oxide. The oxide of Al(0.4)Ga(0.6)As is suitable for high-temperature deposition, but there are criteria for the thickness and oxidation temperature. Thin layers of AlAs oxidized at 475 C are excellent masks and allow precise thickness control. Promising results of selective-area deposition using these aluminum oxide masks have been obtained. High-quality single crystal grew in mask openings uniformly surrounded by dense and fine-grain polycrystalline deposits, producing a planar duplication of the original pattern.

Dry thermal oxidation of GaAs and AlAs has been carried out in an organometallic chemical vapor deposition system. This in situ process performed either before or after an epitaxial growth serves the purposes of surface cleaning and mask generation for selective area epitaxy of various III‐V semiconductors. AlAs oxidized immediately after growth and patterned for the next regrowth provides better oxide‐semiconductor interfaces and minimizes wafer handling. Pre‐epitaxy oxidation at 435 °C on a patterned wafer with AlAs/GaAs areas resulted in a selective oxide mask. Since thermal oxides of GaAs sublime at temperatures >600 °C, a 700 °C pregrowth annealing thus thermally cleans the oxidized GaAs areas while the oxides of AlAs remain as a mask for the following regrowth. Photoluminescence results indicate that high quality regrown interfaces have been obtained.

Optical‐quality GaAs films were successfully grown by molecular beam epitaxy (MBE) through SiO2 insulator windows on GaAs (100) substrates, thus making this selective‐area epitaxy applicable to the fabrication of GaAs optoelectronic integrated circuits. The photoluminescence spectra at 2.2 K consist of several exciton peaks near 820 nm and broader acceptor‐related peaks centered at approximately 830 nm. The spectra are comparable to those observed in high quality planar MBE GaAs grown in other laboratories. The luminescence intensity from the epitaxial layer above the windows is shown by cathodoluminescence to be much higher than that from the polycrystalline GaAs deposited on top of SiO2. From transmission electron microscopy and x‐ray diffractometry it is found that the GaAs grains on the SiO2 grow with their (111) planes preferentially parallel to the SiO2 surface.