Organic Vapor Phase Epitaxy Growth Research Articles

Formation of the Axial Heterojunction in GaSb/InAs(Sb) Nanowires with High Crystal Quality

Switching of the group-III element in III–V nanowire heterostructures is difficult due to the high solubility of group-III atoms in the Au seed particle. In addition, switching from Sb to a different group-V element has not been achieved in binary materials, largely due to its high solubility in Au. In metal–organic vapor phase epitaxy (MOVPE) growth, the use of Sb precursors presents further complications due to reactor background contamination. In this paper, we demonstrate growth of GaSb/InAs(Sb) nanowire heterostructures with potential applications in tunneling devices and study the processes occurring during the transition from GaSb to InAs growth. We show how the heterostructure can be grown with a sharp transition by taking advantage of a growth stop, which occurs naturally as the Au seed particle is emptied of Ga and filled with In. The remaining Sb background in the reactor during the InAs growth results in a finite Sb incorporation into this segment. This has the advantage of suppressing stackin...

Double step structure and meandering due to the many body interaction at GaN(0001) surface in N-rich conditions

Growth of gallium nitride on GaN(0001) surface is modeled by Monte Carlo method. Simulated growth is conducted in N-rich conditions, hence it is controlled by Ga atoms surface diffusion. It is shown that dominating four-body interactions of Ga atoms can cause step flow anisotropy. Kinetic Monte Carlo simulations show that parallel steps with periodic boundary conditions form double terrace structures, whereas initially V-shaped parallel step train initially bends and then every second step moves forward, building regular, stationary ordering as observed during metal organic vapor phase epitaxy or hydride vapor phase epitaxy growth of GaN layers. These two phenomena recover surface meandered pair step pattern observed, since 1953, on many semiconductor surfaces, such as SiC, Si, or GaN. Change in terrace width or step orientation particle diffusion jump barriers leads either to step meandering or surface roughening. Additionally it is shown that step behavior changes with the Schwoebel barrier height. Furthermore, simulations under conditions corresponding to very high external particle flux result in triangular islands grown at the terraces. All structures, emerging in the simulations, have their corresponding cases in the experimental results.

Impact of AlN seeding layer growth rate in MOVPE growth of semi‐polar gallium nitride structures on high index silicon

AbstractWe present metal organic vapor phase epitaxy growth of semi‐polar GaN structures on high index silicon surfaces. The crystallographic structure of GaN grown on Si(112), (115), and (117) substrates is investigated by X‐ray analysis and scanning electron microscopy. X‐ray diffraction was performed in Bragg Brentano geometry as well as pole figure measurements. The results demonstrate that the orientation of GaN crystallites on Si is significantly dependent on thickness of the AlN seeding layer and TMAl‐flow rate. We observe that the crystallographic structures of GaN by applying thin AlN seeding layers grown with high TMAl‐flow rate depend on Si surface direction while they are independent for thicker layers. By applying such seeding layer we obtain single crystalline semi‐polar GaN on Si(112), while GaN structures grown with the same growth parameters on Si(117) show four components of GaN(0002).

Semipolar single component GaN on planar high index Si(11h) substrates

We present metal organic vapor phase epitaxy growth of polarization reduced, single component GaN on nonpatterned Si(112), Si(113), Si(114), Si(115), and Si(116) substrates. We find that the inclination angle of GaN c-axis with respect to the surface normal depends on the angle between Si(111) and above mentioned Si(11h)-surfaces. The growth of the GaN layer is essentially performed as c-axis oriented growth on the naturally occurring Si(111) facets of these Si(11h)-surfaces. The c-axis tilt-angle of GaN crystallites depends on the Si-surface direction and increases from Si(112) to Si(116) planes. GaN layers are investigated by x-ray analysis and scanning electron microscopy.

Correlation between hetero-interface properties and photoluminescence efficiency of Ga(NAsP)/(BGa)P multi-quantum well structures on (0 0 1) Si substrate

The photoluminescence (PL) characteristic of Ga(NAsP)/(BGa)P quantum well heterostructures pseudomorphically grown on (0 0 1) Si substrates are dominated by the compound semiconductor crystal quality in line with local defects and impurities, but also influenced by the hetero-interface morphology. A comparison of the PL line width of multi-quantum well (QW) structures with different QW thicknesses reveals an increase in line width due to interfacial composition undulation. The degree of interface roughness is related to the N concentration of the active material system. A pronounced decline in PL intensity of the QW material is observed when B and N precursors are simultaneous utilized in the metal organic vapor phase epitaxy growth process. In order to preserve the luminescence efficiency a GaP spacer layer is inserted between each B-containing barrier film and the Ga(NAsP) active material system. The minimum required GaP film thickness is linked to the amount of interface undulation. A GaP spacer width of 3 nm is sufficient to maintain the luminescence intensity of Ga(NAsP)/(BGa)P multi-quantum well heterostructures.

MOVPE growth and characterization of a ‐plane AlGaN over the entire composition range

AbstractWe report the metal organic vapor phase epitaxy (MOVPE) growth and characterization of non‐polar (11$ \bar 2 $0) a ‐plane Alx Ga1–xN on (1$ \bar 1 $02) r ‐plane sapphire substrates over the entire composition range. Alx Ga1–xN samples with ∼0.8 μm thick layers and with x = 0, 0.18, 0.38, 0.46, 0.66, and 1.0 have been grown on r ‐plane sapphire substrates. The layer quality can be improved by using a 3‐stage AlN nucleation layer and appropriate V/III ratio switching following nucleation. All a ‐plane AlGaN epilayers show an anisotropic in‐plane mosaicity, strongly influenced by Al incorporation and growth conditions. Careful lattice parameter measurements show anisotropic in‐plane strain that results in an orthorhombic distortion of the hexagonal unit cell, making Al composition determination from X‐ray diffraction difficult. In general lower Al incorporation is seen in a ‐plane epilayers compared to c ‐plane samples grown under the same conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Shallow and deep dry etching of silicon using ICP cryogenic reactive ion etching process

We achieved to etch nanostructures as well as structures with high aspect ratios in silicon using an inductively coupled plasma cryogenic deep reactive ion etching process. We etched cantilevers, submicron diameter pillars, membranes and deep structures in silicon with etch rates between 13 nm/min and 4 μm/min. These structures find applications as templates for metal organic vapour phase epitaxial growth of GaN-based nanostructures for optoelectronic devices or they are the basic constituents of a nanoparticle balance in the subnanogram range and of a thermoelectric generator.

Investigation of optimum growth conditions of InAlN for application in distributed Bragg reflectors

InxAl1−xN is an alloy system which can be lattice matched to GaN, with many potential applications including distributed Bragg reflectors. This work investigated the effect of changing the ammonia flux during metal organic vapour phase epitaxy growth. The indium incorporation increases as the ammonia flux is increased from 44.6 mmol/min to 179 mmol/min, but remains constant for further increases up to 446 mmol/min. The surfaces across this range generally have low surface roughnesses suitable for use in distributed Bragg reflectors. However, some samples have significant surface pit densities, although these are not linked to similar rises in threading dislocations generated at the GaN / InAlN interface.

Preface: Phys. Status Solidi C 7/1

AbstractSymposium J of the E‐MRS 2009 Spring Meeting covered the diversity of the current nitride research ranging from optical, electrical and characterization over growth to processing and devices of nitride materials. There were many excellent talks which provided a nice spectrum about the state‐of‐the‐art of growth and devices based on InN. In an invited talk by Martin Stutzmann, Technische Universität München, the latest developments of GaN‐based sensors were discussed, especially their applications in biology. Highlights of the meeting were, on one hand, new developments of high power light emitting diodes (LEDs). These invited talks were given for UV LEDs by Asif Khan, University of South Carolina, for visible LEDs by Werner Goetz, Philips Lumileds, and for the green light emitters by Christian Wetzel, Rensselaer Polytechnic Institute. On the other hand, Adrian Avramescu, OSRAM Opto Semiconductors presented 500 nm electrically driven InGaN‐based laser diodes and demonstrated that quality improvements of InGaN quantum wells with high indium content as well as an efficient carrier injection makes it possible to achieve lasing up to a wavelength of 500 nm. Acentral contribution of the present proceedings is the Feature Article by Sandra Ruffenach et al. on recent advances in metal organic vapour phase epitaxy (MOVPE) growth of InN [1].The symposium venue had a very pleasant surrounding and was convenient for the participants. The open atmosphere enabled a lot of detailed discussions. In the framework of European research, a major purpose of the meeting was to stimulate the generation of new projects and goals and to promote informal scientific exchange (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Metal organic vapor phase epitaxy growth of single crystalline GaN on planar Si(211) substrates

We present metal organic vapor phase epitaxy growth of polarization reduced, wurtzitic gallium nitride layers with an 18° inclination of the c-axis to the surface normal on planar Si(211) substrates. The growth of this layer is performed as c-axis oriented growth on the naturally occurring Si(111) planes of the Si(211) substrate. Cathodoluminescence measurements on a ∼1.2 μm thick structure reveals that it has a low concentration of basal plane stacking faults and no prismatic stacking fault luminescence.

Structural analysis, elemental profiling, and electrical characterization of HfO2 thin films deposited on In0.53Ga0.47As surfaces by atomic layer deposition

In this work results are presented on the structural analysis, chemical composition, and interface state densities of HfO2 thin films deposited by atomic layer deposition (ALD) from Hf[N(CH3)2]4 and H2O on In0.53Ga0.47As/InP substrates. The structural and chemical properties are investigated using high resolution cross-sectional transmission electron microscopy and electron energy loss spectroscopy. HfO2 films (3–15 nm) deposited on In0.53Ga0.47As are studied following a range of surface treatments including in situ treatment of the In0.53Ga0.47As surface by H2S exposure at 50–350 °C immediately following the metal organic vapor phase epitaxy growth of the In0.53Ga0.47As layer, ex situ treatment with (NH4)2S, and deposition on the native oxides of In0.53Ga0.47As with no surface treatment. The structural analysis indicates that the In0.53Ga0.47As surface preparation prior to HfO2 film deposition influences the thickness of the HfO2 film and the interlayer oxide. The complete interfacial self-cleaning of the In0.53Gas0.47As native oxides is not observed using an ALD process based on the Hf[N(CH3)2]4 precursor and H2O. Elemental profiling of the HfO2/In0.53Ga0.47As interface region by electron energy loss spectroscopy reveals an interface oxide layer of 1–2 nm in thickness, which consists primarily of Ga oxides. Using a conductance method approximation, peak interface state densities in the range from 6×1012 to 2×1013 cm−2 eV−1 are estimated depending on the surface preparation.

Longitudinal bandgap modulated broadband (>150 nm) InGaAs/GaAs MQWs superluminescent diodes by selective area MOVPE growth

The characteristics of broadband superluminescent diodes (SLDs) are presented. The longitudinal bandgap modulated InGaAs/GaAs multiple quantum wells of broadband SLDs are grown by selective area metal organic vapour phase epitaxy (MOVPE) growth. The centre wavelength was 1060 nm. The 3 dB bandwidth was 130 nm and the 10 dB bandwidth was 174 nm. The output power was 0.3 mW.

Process design of the pulse injection method for low-temperature metal organic vapor phase epitaxial growth of AlN at 800 °C

The pulse injection (PI) growth method in which trimethylaluminium (TMAl) and NH 3 are alternately supplied was used to grow AlN layer at 800 °C. It was found that the process parameters in the PI method such as TMAl supply time ( τ TMAl), TMAl partial pressure ( P TMAl), and 1st H 2 purge time ( τ H1) had great influence on the crystal quality and surface morphology. Control of the growth rate to 1 monolayer (ML)/cycle resulted in highly improved crystal quality. 3.91×10 −4 mbar of P TMAl and 1 s of τ H1 were also found to be very effective in realizing high crystal quality showing narrow (0 0 0 2) and (1 0 1¯ 2) full-width at half-maximum (FWHM) values confirmed by high-resolution X-ray diffraction (HRXRD) rocking curve measurement. This is because the agglomeration of initial AlN islands and adducts formation by the gas-phase reaction could be suppressed under these conditions. According to the second ion mass spectroscopy (SIMS) measurement for the AlN layer grown by PI method (PI-AlN), the impurities concentrations of hydrogen, carbon, and oxygen showed several times lower levels than those of AlN layer grown by the conventional continuous method (C-AlN) at same 800 °C. Moreover, the impurities concentrations in PI-AlN layer were almost same with those of C-AlN grown at 1240 °C. It clearly shows the effectiveness of PI method in enhancing reduction reaction by NH 3.

Metal–Organic Vapor Phase Epitaxial Growth Condition Dependences of MnAs Nanocluster Formation on GaInAs (111)A Surfaces

The authors report that the formation of MnAs nanoclusters (NCs) on GaInAs (111)A surfaces strongly depends on metal–organic vapor phase epitaxial growth conditions. It was confirmed from the atomic force microscope observation that deep holes were formed on the surfaces under low V/Mn ratio and high growth temperature conditions, in addition to the formation of MnAs NCs. From the results of cross-sectional transmission electron microscope observation, these deep holes were formed on the underlying GaInAs layers, and MnAs NCs were embedded in the GaInAs (111)A layers. The formation of these embedded MnAs NCs was possibly caused by the phenomenon of “endotaxy”. From the experimental results of thermal treatments of the samples, it was revealed that the deep holes were formed on the GaInAs (111)A surfaces even after the thermal annealing in the atmosphere of Mn source gas and hydrogen. Therefore, we concluded that high AsH3 partial pressure (V/Mn ratio) conditions were required for the MnAs growth on GaInAs (111)A surfaces.

Kinetics of Subsurface Formation during Metal–Organic Vapor Phase Epitaxy Growth of InP and InGaP

InGaP layers grown by metal–organic vapor phase epitaxy (MOVPE) often have an In-rich region within several nanometers from the top of the film, which cannot be explained by normal surface segregation theory. This surface segregation deteriorates the interface abruptness of the InGaP/GaAs system, which is attractive for high-performance devices. This segregation in lattice-matched InGaP/GaAs systems can be explained by considering a “subsurface”, where unstable surface layers play an important role in controlling the composition of grown epi-layers. This subsurface is formed at the beginning of crystal growth, and its thickness is in a steady state under normal continuous epitaxial growth. In this study, the existence of a subsurface during the MOVPE growth of InP and InGaP is experimentally confirmed through kinetic analysis involving a flow modulation method. The kinetic parameters, such as the adsorption and desorption rate constants of In and Ga species, and the crystallization rate from the subsurface are estimated from experimental data and are then used to explain the tendency of In surface segregation in InGaP-MOVPE.

In situ H2S passivation of In0.53Ga0.47As∕InP metal-oxide-semiconductor capacitors with atomic-layer deposited HfO2 gate dielectric

We have studied an in situ passivation of In0.53Ga0.47As, based on H2S exposure (50–350°C) following metal organic vapor phase epitaxy growth, prior to atomic layer deposition of HfO2 using Hf[N(CH3)2]4 and H2O precursors. X-ray photoelectron spectroscopy revealed the suppression of As oxide formation in air exposed InGaAs surfaces for all H2S exposure temperatures. Transmission electron microscopy analysis demonstrates a reduction of the interface oxide between the In0.53Ga0.47As epitaxial layer and the amorphous HfO2 resulting from the in situ H2S passivation. The capacitance-voltage and current-voltage behavior of Pd∕HfO2∕In0.53Ga0.47As∕InP structures demonstrates that the electrical characteristics of samples exposed to 50°C H2S at the end of the metal-organic vapor-phase epitaxy In0.53Ga0.47As growth are comparable to those obtained using an ex situ aqueous (NH4)2S passivation.

Modelling and simulation of MOVPE of GaAs-based compound semiconductors in production scale Planetary Reactors

The paper deals with the global, reactor scale modelling and simulation of metal organic vapour phase epitaxy (MOVPE) growth of GaAs-based III–V compound semiconductor thin films in large production scale Planetary Reactor ® with various wafer load configurations. Reactor hardware and growth process improvements that aim at increased reactant utilisation efficiency, reduced gas consumption and improved layer thickness and compositional uniformity control at low wafer edge exclusion are discussed. The modelling approach consists of the computation of macroscopic gas phase transport phenomena in the process zone e.g. flow, heat and mass transfer, including thin film deposition on hot surfaces. Modelling and simulation results are used to guide the reactor chamber design, gas inlet layout and the choice of process parameters leading to overall productivity enhancement and increased robustness of the process. The model accuracy for MOVPE growth of the AlGaAs and GaInP material system in large reaction chambers is demonstrated, and the advantages of using modelling to optimise hardware and process design are highlighted.

Morphology of interior interfaces in the novel dilute nitride Ga(NAsP)/GaP material system

A novel method is presented which allows to expose and investigate interior interfaces in the Ga(NAsP)/GaP material system by a combination of highly selective etching and subsequent atomic force microscopy. We demonstrate the selectivity of the chemical etchant and prove that structural information and atomic-scale z-resolution is fully preserved when applying the method. A correlation between metal organic vapour phase epitaxy growth parameters and interior interface morphology is confirmed by subjecting compressively strained and lattice matched Ga(NAsP) material to a growth interruption. The interior interfaces of both materials smoothen during growth interruption, and for the compressively strained Ga(NAsP) we obtain a monolayer-structured morphology. The optimization of this material is very interesting from an application point of view as it has shown electrical injection lasing near room temperature and might be applied for optoelectronic integrated circuits based on Si in the future.

Catalyst-free growth of In(As)P nanowires on silicon

The catalyst-free metal organic vapor phase epitaxial growth of In(As)P nanowires on silicon substrates is investigated using in situ deposited In droplets as seeds for nanowire growth. The thin substrate native oxide is found to play a crucial role in the nanowire formation. The structure of the nanowires is characterized by photoluminescence and electron microscopy measurements. The crystal structure of the InP nanowires is wurtzite with its c axis perpendicular to the nanowire axis. Adding arsenic precursor to the gas phase during growth results in a bimodal photoluminescence spectrum exhibiting peak at the InAsP and InP band gap energies.

Nitrogen content of GaAsN quantum wells by in situ monitoring during MOVPE growth

Metal–organic vapor phase epitaxial growth of GaAsN quantum wells is monitored by in situ reflectance measurements. Correlation between the change in the reflectance intensity and nitrogen content of the quantum well is established. The reflectance as a function of time also reveals if there is deterioration of the crystalline quality during growth. This method together with X-ray diffraction and photoluminescence characterization is applied to analyze GaAsN growth using various reactor pressures and TBAs/III molar flow ratios.