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Integration of InGaAs/InAs nanowire on silicon (Si) substrate has been attracting huge attention for opto- and micro-electronics applications. In this work we report selective area epitaxy (SAE) of InGaAs/InAs heterostructure (HS) on Si (111) using metal organic chemical vapor deposition (MOCVD). High quality InAs wurtzite (WZ) segment is grown axially on InGaAs NW when the arsine (AsH 3 ) supply is low. The growth phenomenon behind the axial InAs HS on InGaAs is attributed due to surface segregation and sidewall diffusion of indium (In) adatoms on the surface of the InGaAs nanowire at In-rich/arsenic (As)-limited region. For high AsH 3 flow, As coverage impedes InAs segment formation.

Avalanche photodiodes are fabricated and characterized, using a single diffusion fabrication process with the surface patterned by selective area growth prior to diffusion. Raster mapping of the photocurrent near the breakdown voltage is used to characterize the electric field distribution in the multiplication layer. Devices fabricated with the precursor CBrCl 3 introduced during selective area epitaxy show a smoother surface morphology and effective edge breakdown suppression, while those fabricated without CBrCl 3 have a rougher surface morphology and exhibit evidence of premature edge breakdown at the corners of the device along specific crystal orientations. Comparison of the dark current — voltage curves below breakdown shows a reduction of dark current associated with the use of CBrCl 3 , as well as with the inclusion of floating guard rings in the device design.

Because of its indirect bandgap nature, Gallium phosphide (GaP) in its conventional zinc blende crystal structure, has only limited optoelectronic applications in the visible light spectrum. The WZ structured GaP, on the other hand, has a direct band gap between 2.18 and 2.25 eV, ideal for a green-yellow spectral range light emitting devices. It is well known that the crystal structure of the III-V materials can be modulated when they are grown in nanowire (NW) form via the VLS/SAE mechanism so that either a ZB, WZ, or an intermixing of the ZB and WZ structured III-V NWs can be achieved. The realization of WZ GaP NWs were experimentally verified but the mechanism of selecting a crystal structure while NW is grown are still controversial. However, a common factor that promotes the realization of WZ structured NW is the suppression of the lateral overgrowth, because the ZB structure has the lowest surface energy at $\{11^{-}0\}$ side facets of the hexagonal NW. On the other hand, the nucleation at side $\{11^{-}00\}$ facets of WZ NW is difficult so that the hexagonal WZ NWs tend to grow more vertically with less lateral overgrowth. Understanding, developing, and controlling the growth condition of GaP NWs to form WZ structures would be crucial to practical applications of this highly promising material system. In addition, integrating GaP on silicon is also challenging. Recently, GaP nanowire (NW) heteroepitaxial growth have been demonstrated on Si (111) and Si (100) substrates using the VLS method. However, selective area epitaxy (SAE) of GaP NWs on Si (111) substrate or even on the GaP (111) substrate have not been well developed yet.

Growth of III-V materials on Si could enable dramatic cost reduction for III-V PV by eliminating the need for expensive III-V substrates and enabling high-efficiency tandem solar cells. The direct heteroepitaxy of III-V materials on Si for high-efficiency photovoltaics has progressed greatly in recent years, but most studies have focused on off-cut wafers polished using an expensive chemical-mechanical planarization process (which is not used for commercial solar cells). Alternative growth approaches are needed that can enable the integration of high material quality III-Vs with PV-grade Si materials. Here we demonstrate the use of cost-effective patterning and etching approaches to create templates for selective area epitaxy on PV-grade Si substrates. We investigate the nucleation of III-V materials on these substrates.

Metalorganic chemical vapor deposition (MOCVD) has been the epitaxial growth method of choice for lasers and other photonic devices for nearly forty years. Here we very briefly review selected aspects of MOCVD selective area epitaxy (SAE) and nanostructure self-assembly, to patterned nano-structure growth.

Photonic crystals provide unprecedented control over light emission, absorption and propagation, which has led to the proposal of a large variety of optoelectronic devices. Three-dimensional devices with electronic functionality have however remained elusive, as fabrication of three-dimensional, electrically active nanostructured materials remains complex. Numerous techniques have been demonstrated to fabricate 3D photonic and plasmonic crystals, including colloidal crystallization, phase mask and multibeam interference lithography, direct laser writing, photolithography, and wafer bonding, but, most of these techniques result in amorphous or polycrystalline material which does not possess the required electronic properties for application in optoelectronics. In this work we demonstrate a method of forming 3D photonic and plasmonic crystals from single crystal III–V semiconductors by metal-organic vapor phase epitaxy (MOVPE). We employ a templatebased fabrication method and grow semiconductor material to fill the structure using a form of selective area epitaxy. The epitaxial growth process (originating at the substrate, in contrast to conformal growth) is much the same as the growth of planar III-V devices in that light emitting layers (e.g. quantum wells), cladding layers, electrically doped layers, etc may all be grown in a single process. Thus, the layers of an optoelectronic device may be defined by the MOVPE growth parameters while the photonic crystal structure is simultaneously imparted to the material using the 3D template. To demonstrate the potential of this technique we have fabricated vertically emitting LED's with embedded InGaAs QW's. The fundamental behaviors of this growth technique will be discussed, including prevention of polycrystalline nucleation, doping, and steps for fabrication of light-emitting heterostructures.

Highly uniform InGaN quantum dots (QDs) were grown by metal-organic chemical vapor deposition utilizing self-assembled diblock copolymer nanopatterns. This approach resulted in ultra-high InGaN QD density of 8 × 1010 cm−2.

Using GSMBE with ammonia on (0001) sapphire substrates, AlN/AlGaN nanostructured short period superlattices (SPSLs), with respective well and barrier thickness from 0.5 to 1 nm and from 0.75 to 1.5 nm, have been shown to have energy gaps in the deep UV suitable for light emitting diodes (LEDs) and photodetectors (PDs) operating down to 247 nm. Performance of LEDs and PDs is limited by factors including efficiency of radiative recombination and absorption in the active region and electrical resistivity of p-type wide bandgap SPSLs. Based on MOVPE, we have used selective area epitixy (SAE) to grow InGaN/GaN quantum structures. By patterning SiO2 hard mask materials on planar sapphire substrates, we have grown various shapes including pyramidal stripes with In x Ga 1−x N multiple quantum wells. The structures at the apex are found to have very high In content with corresponding optical emission in the green wavelength range and excellent uniformity.

An accurate and repeatable sub-10 nm patterning technique is proposed and demonstrated using atomic-layer deposition. Together with selective area epitaxy, this technique is suitable for the fabrication of III-nitride quantum dots.

We studied photoluminescence of InGaN site-controlled nanostructures formed by selective area epitaxy. We developed a theoretical model for the nanoscale growth evolution and used this model for the optimization of optical qualities of InGaN nanostructures.

InAs patterned QDs (PQDs) preferentially nucleate on faceted GaAs pyramidal buffers using selective area epitaxy by metalorganic chemical vapor deposition. The photoluminescence (PL) wavelength is shown to be controlled by a single growth parameter, the growth time, without affecting the density of PQDs. Strong room temperature PL emissions over 1.5 mum from PQDs are demonstrated. The long wavelength emission is attributed to the large QD size and the partial strain energy relaxation of PQDs.

We report fabrication of site-controlled, highly uniform and dense (>=1e10/cm2) InGaN multiple stacks of quantum dots using selective area epitaxy in MOCVD. The dot height and lateral dimension are 3 nm and 30 nm, respectively.

We present results on integrated photonic devices fabricated using InGaAs quantum-dots. Selective-area MOCVD is used to tune the bandgap of epitaxial layers for device integration.

We demonstrate that InAs and InGaAs quantum dots can be grown selectively in specific regions of GaAs substrates using selective-area MOCVD. Growth parameters can be controlled to obtain high density ( /spl sim/10/sup 10//cm/sup 2/) of defect free quantum dots. Emission spectra from these selectively grown dots are presented and are comparable in linewidth to that from dots grown on unpatterned substrates. We propose that this growth scheme can be used for fabrication of quantum dot lasers integrated with waveguides.

This report shows for the first time the simultanous growth of InP/GaInAsP heterostructures having vertical and horizontal interfaces, demonstrated with multi (5) quantum well structures. The surface selective growth (SSG) in metalorganic MBE (MOMBE or CBE) enables on the one hand selective area epitaxy and on the other hand it allows to obtain vertical side walls at selectively grown structures. In addition SSG can provoke that the GaInAsP material composition is different on horizontal (100) and vertical (01 1 ) planes. This effect is utilized in order to allocate the results from focused photoluminescence measurements to the different types of superlattices. It is discussed that the proposed growth technique includes an attractive way to produce quantum wire systems besides the realization of vertical superlatices.

InP/InGaAs/InP heterostructures were selectively grown in an array of 60 nm holes on a 90 nm pitch by MOCVD. The pattern was defined photolithographically directly in hydrogen silsesquioxane, a spin-on-glass, obviating the need for pattern transfer processes.

The threshold and spectral characteristics of patterned quantum dot lasers fabricated by selective area MOCVD crystal growth are presented Full three-dimensional confinement of carriers in an engineered quantum structure is demonstrated.

The use of an InGaAs quantum well as the active layer of a photonic crystal microcavity is problematic in that the perforation of the quantum well creates nonradiative recombination sites. We propose to eliminate this problem by spatially restricting the well to exist only in the photonic crystal defect region. By inhibiting growth of the quantum well in the region that will be etched during the formation of the photonic crystal, we anticipate greatly diminished nonradiative recombination. The crystal is grown by a three-step metal-organic chemical vapor deposition growth process employing nanolithographic selective area epitaxy for the quantum well active layer followed by a second lithographic layer and a dry etch process to form the photonic crystal. The quantum well is designed to luminescence between 1025 and 1050 due to growth enhancement effects created by the selective area epitaxy. The photonic crystal parameters are designed to vary the photonic bandgap over this range.

We demonstrate that selective-area-epitaxy can be used to selectively tune the properties of InGaAs quantum-dots in different regions of the same wafer. We report single step, MOCVD growth of different sized dots, luminescing at wavelengths spread over a range of 100 nm

High speed and low chirp light sources are among the most essential components in long distance multigigabit optical communication systems. InGaAsP-InGaAsP electroabsorption (EA) modulator integrated DFB-LDs (EMILD) have attracted special interest because of their small size, low operating voltage and low chirp. In this paper, the optical and electrical characteristics of an InGaAs-InGaAsP MQW EMILD were studied.

Improvements in selective area epitaxy (SAE) of InP have been achieved by optimizing the epitaxial parameters in metal-organic vapor-phase epitaxy (MOVPE). The significant effect of V/III ratio on the shape of the selectively grown ridge allows the tailoring of ridge geometries for device applications: at high V/III ratios, ridges with vertical side walls can be obtained on substrates with a slight appropriate misorientation. The data show that in contrast to metal-organic molecular-beam epitaxy (MOMBE) for SAE in MOVPE both surface kinetics (diffusion, adsorption-desorption relation) and gas phase diffusion play an important role; in MOMBE only surface kinetics is present and is almost comparable to the mechanisms found in the present study. The results are described by a qualitative model taking into account the dependence of the surface mobility of the adatoms on group V adsorption flux. The reduction of the adatom surface diffusion length should have significant consequences for selective growth of ternary and quaternary layers. These results will also impact selective area growth in the vicinity of mesa stripes, which is important for the monolithic integration of a laser ridge and a waveguide. >

The authors describe the use of selective area epitaxy to prepare monolithically integrated lasers and heterostructure bipolar transistors (HBTs) based on InGaAs(P)/InP. The laser is a capped mesa buried heterostructure structure grown by metal-organic chemical vapor deposition (MOCVD) and optimized for fiber communications. The HBT structures were grown by metal-organic molecular beam epitaxy (MOMBE) on the semi-insulating current confining layers of the lasers. The quality of selectively grown HBTs is illustrated in the Gummel plot and common emitter output characteristics. The DC performance of an integrated structure is illustrated. The laser is driven with the collector current of the HBT. Threshold is achieved at a base current of I/sub B/=360 /spl mu/A. Light output of the laser is linear to at least 10 mW. Preliminary experiments show the bandwidth of the integrated device to be in excess of 3 GHz. >

Buried heterostructure lasers are formed by first growing a planar broad area structure, masking with a dielectric stripe and etching of mesas, usually down to the substrate. In the second growth step, current confining layers are grown between the mesas. A successful regrowth process must provide a planarized final surface, which is a particularly important issue when MOVPE is used, since this technique tends to result in mask overgrowth and rough morphology adjacent to the mask edge. In this paper the kinetics of the regrowth has been studied using MOVPE at atmospheric pressure in a Thomas Swan reactor. The contours of InP regrowth were observed by growth interruption at each 0.2 /spl mu/m of thickness and inserting a 1.5 nm thick lattice matched InGaAs marker layer or by alternating doping between Fe and S at each 0.2 /spl mu/m of layer growth. The doping or compositional markers were easily stained to show the growth contours. >

Devices based upon the monolithic integration of a distributed feedback (DFB) laser with an electroabsorption modulator offer considerable promise as the next generation of sources for high speed optical communication systems. Their advantage over directly modulated diode lasers stems from the reduction of wavelength chirp, which is important for high frequency operation. One interesting route to devices of this type uses selective area epitaxy (SAE) of multi quantum well structures, to laterally pattern the band gap wavelength. This allows a low insertion loss of the laser light into the modulator to be achieved, by red shifting the laser emission wavelength with respect to the modulator band edge. This is done by fabricating the emitter in an area of perturbed epitaxy, where the quantum wells are thicker. The use of SAE can exacerbate growth imperfections which result when "difficult to grow" vertical structures are required. This paper discusses such problems, and the ways in which they can be ameliorated. >

For the fabrication of advanced optoelectronic devices metalorganic growth technologies will play an important role in the next years: metalorganic molecular beam epitaxy (MOMBE) and metalorganic vapor phase epitaxy (MOVPE). Both technologies are basically comparable. The former technology, however, uses a much lower system pressure so that a carrier gas is not required for the growth process. In this case due to the molecular nature of the gas beams gas phase reactions can be excluded. In MOMBE the chemical reactions for crystal growth take place at the growth front leading to surface selective growth (SSG). The mass transfer of reactants to the surface is not affected by desorption from masked or different surface areas so that high perfection selective area epitaxy (SAE) can be achieved. In MOVPE, however, additionally to surface reactions, effects of gas phase reactions and gas phase interdiffusion have to be taken into account. >

Selective area epitaxy can be easily obtained at atmospheric pressure conditions by introducing a compound preventing nucleation on the masked areas or by choosing a proper set of mask size. These two approaches have been investigated and conclusions have been made on a laser and waveguide integration realisation. >

For the first time we present the integration of a tunable buried four-section DBR-laser butt coupled to a directional coupler based on semi-insulating strip loaded (InGaAsP/InP):Fe waveguides by using selective area epitaxy with large mask areas. Good planarity after the epitaxial regrowth of the waveguide layers has been achieved applying a special preparation of the laser mesa. Average coupling efficiencies of 52% and best values of 63% have been realized. The optical power of the guided light at each output port of the coupler exceeds 1 mW. >

Strained-layer InGaAs-GaAs-AlGaAs single quantum well buried heterostructure lasers grown by selective-area MOCVD are described. Threshold currents of 2.65 mA for an uncoated device and 0.97 mA for a coated device have been obtained. A peak optical output power of 170 mW per uncoated facet for a device with a 4 /spl mu/m active region width was also achieved. Peak emissions wavelengths range from 0.956 to 1.032 /spl mu/m. >

In this work, we have fabricated delta doped quantum wire structures with sharp tips and smooth side walls. Si delta doped InGaAs/GaAs quantum wire structures were grown on SiO/sub 2/ masked GaAs substrate by low pressure metalorganic chemical vapor deposition by using selective area epitaxy. The effects of the growth parameters such as growth rate, V/III ratio, growth temperature in selective epitaxy were investigated for GaAs/Al/sub 0.5/Ga/sub 0.5/As multilayer structures. To characterize and analyze the selectively grown structures, scanning electron microscopy and temperature dependent photoluminescence were used. The emission peak from quantum wires was observed at 975 nm. With increasing of temperature the emission intensity from side wall quantum wells decreased abruptly. But the intensity from quantum wires decreased slowly compared to that of side wall quantum wells and it became even stronger at about 50 K. The carrier capture processes also discussed.

For the first time multi-mode interference (MMI) power splitters have been fabricated by selective area growth, using our novel metal-organic vapor phase diffusion enhanced selective area epitaxy (MOVE/sup 2/) process which features extremely wide-range in-plane bandgap control and high design flexibility and therefore is very suitable for photonic integration. Excess losses as low as 2 dB have been obtained for MMI power splitters with smooth and sufficiently flat waveguide structures including S-bends.

We combine selective area epitaxy (SAE) and a newly discovered resist-less SRP technique to completely eliminate the use of photoresist during the definition of source, gate and drain. In this way the gate and channel regions are protected from exposure to resist and associated chemicals. Photoresist is only used to carry out contact enhancement after the fabrication of the device. This approach opens up the opportunity for in-situ fabrication of novel device structures through the use of various combinations of SAE and SRP. Here we show a MESFET as a demonstration of this technology.

The possibility of finding an approximate solution for the Laplace equation in two dimensions with special boundary conditions is explained. These conditions correspond to the description of a Reduced Surface Interaction Model (RSIM), appropriate for describing the problem of selective area epitaxy. Very good agreement with computed results using the standard finite difference technique for practical growing conditions of InP and GaAs was obtained. However a significant reduction of computing time (from hours to minutes) is observed.

Monolithically integrated electroabsorption modulated laser grown by selective-area epitaxy using MOVPE is a very essential source for multigigabit long-haul WDM transmission systems employing EDFAs. Such an EML offers very low chirp, low drive voltage, long-term reliability and compact size. >

Summary form only given. In this talk, we will review the progress in selective area epitaxy using organometallic chemical vapor deposition (OMCVD) on substrates with patterned masks. Selective area epitaxy enables one to obtain lateral control of thickness, composition and doping.

We have demonstrated that a novel masking technique for low energy quantum well intermixing (QWI), comparable to selective area epitaxy, can be used for the realization of multiple bandgaps in the production of WDM quantum well laser sources, as well as other photonic integrated circuits for use in 1.55 /spl mu/m optical fibre communications applications.

Recent ultra-fast optical-fiber communication systems require various functional optical components, such as all optical switches. We have fabricated InGaAsP/InP Mach-Zehnder interferometer optical switches monolithically integrated with semiconductor optical amplifiers (SOAs) using a single-step MOVPE selective area growth and two types of patterning and etching process. Preliminary optical switching experiment revealed large carrier-induced index change in the selective-area-grown multiple quantum well SOAs. Furthermore, all optical switching experiment has successfully been demonstrated in these fabricated devices.

A novel method of quantum dot selective area epitaxy of InAs quantum dots using an InGaAs pattern is presented. Indium segregation from an underlying InGaAs layer allows for preferential growth of InAs quantum dots on InGaAs when additional material is deposited. By using standard lithography techniques, selective area epitaxy was achieved on 20% InGaAs layers with a dot density of 3/spl times/10/sup 10/ cm/sup -2/ without the need for subsequent regrowth steps. The selective area quantum dot epitaxy was also observed to occur on self-organized 100 nm InAs 2D mesas with a high local selective area quantum dot density of 3.1/spl times/10/sup 12/ cm/sup -/2.

InAs and InAs/GaSb/AlSb based resonant interband tunneling diodes are grown selectively in open windows on patterned GaAs substrates. The patterning is carried out by using a recently discovered resistless process wherein the GaAs surface is modified in the light exposed regions into forming a stable gallium oxide mask that can withstand InAs selective growth conditions. The one-step process used here replaces multi-step processes typically used to pattern the silicon nitride or oxide conventionally used as a mask for selective growth. It brings about many advantages such as cleanliness, reduction in cycle time, and improved compatibility with cluster tools.

Using oxide-patterned substrates, we have selectively grown GaAs mesas with (100) top facets ranging from several /spl mu/m to less than 250 nm in width and InAs quantum dots (QDs) on top of these facets. For a given total InAs coverage, the dot density varies with the facet width. The QDs also tend to form at the facet edges. These observations suggest a strong surface diffusion effect of In-containing species adsorbed on the various GaAs facets of a mesa. By designing the oxide pattern in an appropriate manner, a two-dimensional array of QDs could be positioned in a pre-determined configuration at specific wafer locations.