Growth Of In0 Research Articles

Importance of liquid phase epitaxy on achieving near-lattice-matched growth of In0.145Ga0.855As0.132Sb0.868 layers on GaSb(100) substrates

We report the growth of In0.145Ga0.855As0.132Sb0.868 layers on GaSb(100) substrates by the liquid phase epitaxy (LPE) technique using the ramp-cooling method. We achieved a near-lattice-matched epitaxial growth with a lattice mismatch of between the quaternary layer and GaSb(100) substrate due to optimal growth parameters. Aberration-corrected scanning transmission electron microscope (AC-STEM) confirmed the high crystalline quality of the quaternary layer and the low lattice mismatch in the heterostructure, without the presence of linear or planar defects. Also, the Secondary Ion Mass Spectrometry (SIMS) technique evidenced a uniform distribution of the atomic elements along the quaternary layer and an abrupt interface between the In0.145Ga0.855As0.132Sb0.868 layer and the GaSb substrate. Plasmon-phonon interactions were observed by Raman spectroscopy indicating that the crystalline quality increases at greater depth in the sample with respect to the surface. The quaternary layer presented a uniform and flat morphology, and luminescence emission attributed to the recombination of bound exciton states at 641 meV. The structural, chemical, and optical properties of the In0.145Ga0.855As0.132Sb0.868 layer demonstrated that it could be auspicious material for infrared range optoelectronic applications. Likewise, the LPE technique successfully shows that it should be used to grow near-lattice-matched heterostructures.

Impacts of growth conditions on InAlBiAs electrical properties and morphology

As a highly mismatched alloy class, dilute bismuthide materials exhibit strong valence band-Bi impurity state interactions, leading to large bandgap bowing parameters and strong spin–orbit coupling due to the inclusion of Bi in III-V semiconductors. Such properties make the dilute bismuthides ideal candidates for devices requiring band and strain engineering, particularly those in the infrared regions. In this work, the molecular beam epitaxy growth of the dilute bismuthide InxAl1−xBiyAs1−y on InP is studied. To address challenges universally faced in dilute bismuthide growth, a growth–space diagram is constructed to better understand the conditions needed for Bi incorporation and droplet-free growth of the class of dilute bismuthide materials. From this understanding, high-quality, droplet-free growth of In0.52Al0.48BiyAs1−y with up to 5.1% Bi is demonstrated. The n-type unintentional doping of these films is found to be ∼1013–1015 cm−3 with a free carrier mobility of ∼700–1500 cm2/(V s). From these films, the compressive strain induced by Bi incorporation is measured to be (0.190 ± 0.004)% strain/(% Bi) for In0.52Al0.48BiyAs1−y. Using this value to offset strain, lattice-matched InxAl1−xBiyAs1−y on InP is demonstrated.

InAlAs/InGaAs/InP heterostructures for microwave photodiodes grown by molecular beam epitaxy

Pre-epitaxial (001)InP substrate cleaning, growth of In0.52Al0.48As/In0.53Ga0.47As heterostructures lattice-matched to InP substrate by molecular beam epitaxy technique and manufacturing processes of microwave photodiodes with Schottky barrier are developed in this work.

MOCVD Growth of High Quality InGaAs HEMT Layers on Large Scale Si Wafers for Heterogeneous Integration With Si CMOS

We report on the growth of In0.30Ga0.70As channel high electron mobility transistor (HEMT) epi-layers on a 200-mm Si substrate by metal-organic-chemical-vapor-deposition. The HEMT layers were grown on the Si substrate by using a ~3- ${\mu }\text{m}$ thick epitaxial buffer composing of a Ge layer, a GaAs layer, and a compositionally graded and strain relaxed InAlAs layer. The optimized epitaxy has a threading dislocation density of less than $2 {\times } 10^{{7}}$ cm−2 and a root mean square surface roughness of ~6.7 nm. The device active layers include a ${ {\delta } }$ -doped InAlAs bottom barrier, a ~15-nm thick InGaAs channel, a ~8-nm InGaP top barrier layer and a heavily doped InGaAs contact layer. MOSHEMTs with channel length down to 130 nm were fabricated. The devices achieve a peak transconductance of ${\sim }450 ~{\mu }\text{S}/ {\mu }\text{m}$ at ${V} _{ D}$ of 0.5 V. The peak effective mobility ( ${\mu }_{\text {eff}}$ ) in a device with a channel length of 20 $ {\mu }\text{m}$ device channel was ~3700 cm2/ $\text{V} {\cdot }\text{s}$ .

Epitaxial low-temperature growth of In0.5Ga0.5As films on GaAs(100) and GaAs(111)A substrates using a metamorphic buffer

A complex investigation of epitaxial In0.5Ga0.5As films grown on GaAs substrates with crystallographic orientations of (100) and (111)A in the standard high- and low-temperature modes has been performed. The parameters of the GaAs substrate and In0.5Ga0.5As film were matched using the technology of step-graded metamorphic buffer. The electrical and structural characteristics of the grown samples have been studied by the van der Pauw method, atomic force microscopy, scanning electron microscopy, and transmission/ scanning electron microscopy. The surface morphology is found to correlate with the sample growth temperature and doping with silicon. It is revealed that doping of low-temperature In0.5Ga0.5As layers with silicon significantly reduces both the surface roughness and highly improves the structural quality. Pores 50–100 nm in size are found in the low-temperature samples.

Growth and structure of In0.5Ga0.5Sb quantum dots on GaP(001)

Stranski-Krastanov (SK) growth of In0.5Ga0.5Sb quantum dots (QDs) on GaP(001) by metalorganic vapor phase epitaxy is demonstrated. A thin GaAs interlayer prior to QD deposition enables QD nucleation. The impact of a short Sb-flush before supplying InGaSb is investigated. QD growth gets partially suppressed for GaAs interlayer thicknesses below 6 monolayers. QD densities vary from 5 × 109 to 2 × 1011 cm−2 depending on material deposition and Sb-flush time. When In0.5Ga0.5Sb growth is carried out without Sb-flush, the QD density is generally decreased, and up to 60% larger QDs are obtained.

The effects of zinc-doping on the composition of InGaAsP layers grown by MOCVD

We report on the effects of Zn-doping using diethylzinc (DEZn) on the growth of In1−xGaxAsyP1−y quaternary layers (x=0.18–0.41 and y=0.34–0.76) by metalorganic chemical vapour deposition. Independent of the quaternary layer compositions, a systematic reduction (increase) in Indium (Gallium) was observed. This was accompanied by a reduction in the overall growth rate, and increased tensile strain, with increasing DEZn flow. In contrast, the dependence of arsenic/phosphorus incorporation on DEZn flow was found to depend on the surface stoichiometry. We show quantitatively that the observed tensile strain can be explained by compositional variations caused by the Zn-doping process. These results suggest that DEZn affects both homogeneous and heterogeneous processes during the growth of InGaAsP layers.

Growth and optimization of InxGayAl1−x−ySb buffer layers for electronic and optoelectronic applications

InxGayAl1−x−ySb alloys have been grown by molecular beam epitaxy for use as a buffer layer for growing semiconductors on GaAs substrates with lattice constants beyond that of AlSb. This is an extension of the use of AlxGa1−xSb alloys to accommodate for the lattice mismatch with semi-insulating GaAs substrates. The growth of In0.21Ga0.19Al0.6Sb with a 6.2 Å lattice constant on semi-insulating GaAs substrates is the focus of this work. Several measures of the quality of a 1 μm-thick In0.21Ga0.19Al0.6Sb layer improved when the growth temperature was increased from 460 to 600 °C. Atomic force microscopy root-mean-square values decreased from 2.9 to 1.8 nm and the peak-to-valley values decreased from 17.7 to 9.7 nm. In addition, double crystal x-ray diffraction ω-2Θ spectra linewidths decreased from 568 to 482 arc sec. At the lower growth temperatures, several photoluminescence (PL) peaks associated with radiative recombination from regions with different alloy compositions were found. However, on increasing the growth temperature a single PL line was observed, strongly suggesting a more uniform alloy composition.

The growth of In0.5Ga0.5N and InN layers on (1 1 1)Si using nanorod intermediate arrays

Molecular beam epitaxy has been used to grow continuous overlayers of In0.5Ga0.5N and InN on (111)Si, via growth of an intermediate nanorod arrays. Transmission electron microscopy showed that few threading dislocations are generated during nanorod growth, and are subsequently confined to twist grain boundaries 1–2μm apart in the overlayer. In the In0.5Ga0.5N growth, the nanorods formed core–shell hexagonal wurtzite structures with In-poor surfaces, with lateral growth leading to grains with cubic zinc blende structure. High spatial resolution cathodoluminescence imaging showed that the In0.5Ga0.5N overlayers luminesced strongly, with evidence of compositional variations on the 1–2μm scale. The reasons for compositional variations and the growth of cubic material are discussed.

Effects of matrix layer composition on the structural and optical properties of self-organized InGaN quantum dots

Self-organized InGaN quantum dots (QDs) with emission wavelength from green to red range have been grown on GaN templated c-plane sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The effects of matrix layer composition on the structural and optical properties of InGaN QDs have been investigated. A continued growth of QDs is observed during the growth of In0.1Ga0.9N matrix layer, which results in an increase of the QDs' size. By using In0.1Ga0.9N matrix layer instead of GaN one, the annealing induced blue-shift in emission energy of the InGaN QDs can be suppressed. After the growth of top GaN cap layer, a larger red-shift caused by the quantum confined Stark effect is observed in the sample with In0.1Ga0.9N matrix layer. Employing this method, InGaN QD sample emitting at 615 nm with an internal quantum efficiency of 24.3% has been grown. The significance of this method is that it allows a higher growth temperature of InGaN QDs with emission wavelength in the green range to improve the crystalline quality, which is beneficial to enhance the efficiency of green InGaN QD light-emitting-diodes and laser diodes.

Design of InxGa1−xAs buffer layers for epitaxial growth of high-quality In0.3Ga0.7As films on GaAs substrates

A phase field model is developed to simulate In0.3Ga0.7As thin films grown on an GaAs substrate with different buffer layer structures. Using this newly developed phase field model, an optimal step graded InxGa1−xAs buffer layer structure with four sub-layers of x = 0.09, 0.18, 0.27, and 0.33 is then proposed for epitaxial growth of high-quality In0.3Ga0.7As film on GaAs substrate. The strain distribution analysis by using the phase field model reveals that the compressive strain in this optimal heterostructure is partially balanced by the tensile strain caused by the uppermost two layers of In0.3Ga0.7As grown on top of In0.33Ga0.67As, which results in high-quality In0.3Ga0.7As film. The subsequent epitaxial growth of In0.3Ga0.7As films on GaAs substrates demonstrates that the surface RMS roughness and the full width at half maximum of X-ray rocking curve of as-grown In0.3Ga0.7As film with the optimal buffer layer structure are as low as 0.56 nm and 116′′, respectively, indicating very high film quality. These experimental results confirm the high effectiveness of the proposed approach to design buffer layer structure using our newly developed phase field model. This phase field model should be able to extend to hetero-epitaxial growth of other material systems apart from InGaAs.

Influence of GaAs(0 0 1) pregrowth surface morphology and reconstruction on the growth of InGaAs layers

The influence of pregrowth surface morphology and reconstruction upon the growth of In0.15Ga0.85As alloy layers was investigated. After obtaining different pregrowth surfaces, depositions of InGaAs were carried out by molecular-beam epitaxy (MBE). The real space ultrahigh vacuum scanning tunneling microscopy (STM) images showed the disciplinary changes between GaAs and InGaAs surface morphology. Reflection high energy electron diffraction (RHEED) has also been used to estimate InGaAs deposition. As STM images and RHEED oscillations showed, heteroepitaxial surface quality greatly depends on initial state of surface even form the earliest stages of deposition. Two reasons of the effects are proposed, a conjecture for the formation of surfaces morphology and its influence on subsequent growth is also proposed.

Growth of In0.25Ga0.75As quantum dots on GaP utilizing a GaAs interlayer

Coherent In0.25Ga0.75As quantum dots (QDs) are realized on GaP(001) substrates by metalorganic vapor phase epitaxy in the Stranski-Krastanow mode utilizing a thin GaAs interlayer prior to In0.25Ga0.75As deposition. Luminescence is observed between 2.0 eV and 1.83 eV, depending on the thickness of the In0.25Ga0.75As layer. The critical thickness for the two-dimensional to three-dimensional transition of the layer is determined to 0.75 to 1.0 monolayers. A mean activation energy of 489 meV for holes captured by In0.25Ga0.75As quantum dots is measured by deep-level transient spectroscopy, yielding a hole storage time of 3 µs at room temperature.

Electrical analysis of three-stage passivated In0.53Ga0.47As capacitors with varying HfO2 thicknesses and incorporating an Al2O3 interface control layer

The atomic layer deposition of high dielectric constant oxides like HfO2 on III-V substrates such as In0.53Ga0.47As leads to a poor interface, with the growth of In0.53Ga0.47As native oxides regardless of the surface pretreatment and passivation method. The presence of the native oxides leads to poor gate leakage current characteristics due to the low band gap of the native oxides and the presence of potential wells at the interface. In addition, the poor quality of this interface leads to very large interface state defect densities, which are detrimental to metal-oxide-semiconductor-based device performance. A wide band gap interlayer replacing the native oxide layer would remove the potential wells and provide a larger barrier to conduction. It may also assist in the improvement of the interface quality, but the problem remains as to how this native oxide interlayer cannot only be removed but prevented from regrowing. In this regard, the authors present electrical results showing that the atomic layer deposition (ALD) growth of a thin (∼1 nm) Al2O3 layer before the ALD growth of HfO2 causes a removal/reduction of the native oxides on the surface by a self-cleaning process without subsequent regrowth of the native oxides. As a result, there are significant improvements in gate leakage current densities, and significant improvements in the frequency dispersion of capacitance versus gate voltage, even when a defective In0.53Ga0.47As epitaxial layer on an InP substrate is employed. Measurements at different temperatures confirm that the frequency dispersion is mainly due to interface state defect responses and another weakly temperature dependent mechanism such as border traps, after accounting for the effects of nonideal In0.53Ga0.47As epitaxial layer growth defects where applicable.

Deep traps in GaAs/InGaAs quantum wells and quantum dots, studied by noise spectroscopy

Remotely doped In0.35Ga0.65As layers of different coverages 6, 9, 11, and 13 ML were grown by molecular beam epitaxy on (100) GaAs. Quantum dot (QD) nucleation was observed in situ by reflection high-energy electron diffraction at 8 ML growth of In0.35Ga0.65As, while for 6 ML, only two-dimensional (2D) growth was observed. Atomic force microscopy, low temperature photoluminescence, and Hall effect measurements confirmed this transition from 2D to three-dimensional growth. Low-frequency noise studies have been performed to probe defects in such heterostructures throughout the transition from a highly strained quantum well to QDs. Results were compared to a bulk n-type GaAs reference sample. We revealed three main defects in GaAs with activation energies of 0.8, 0.54, and 0.35 eV. These defects with the same activation energies were found in all samples. However, structures containing In0.35Ga0.65As QDs show an additional peak at low temperatures due to the presence of defects which are not observed for reference GaAs and quantum well samples. Detailed analysis shows that for 9 and 11 ML In0.35Ga0.65As QD samples this peak corresponds to the well known M1 defect in GaAs with an activation energy of 0.18 eV, while for a coverage of 13 ML the defect was found to have an activation energy of 0.12 eV. All defects were characterized quantitatively in terms of their activation energy, capture cross section, and density. These studies indicate that noise spectroscopy is a very sensitive tool for electronic material characterization on the nanoscale.

In(Ga, Al)As quantum dot/wire growth on InP

The authors have investigated the growth of dots/wires on InP substrates by tuning the In(Ga, Al)As compositions for dots/wires and buffer layers. Dots and wires with compositions including InAs, In0.95Al0.05As, In0.95Ga0.05As, and In0.90Ga0.10As were grown on In0.53Ga0.26Al0.21As and In0.52Al0.48As buffer layers, respectively. In(Ga)As nanostructure grown on InAlAs ternary buffer layer forms elongated dots along the [0-11] direction. On the other hand, In0.95Ga0.05As and In0.90Ga0.10As nanostructures grown on InGaAlAs buffer layer form quantum wire arrays of high uniformity. The In0.90Ga0.10As quantum wires have a photoluminescence spectrum of emission peak at λ∼1680nm and a narrow full width at half maximum of 65meV at 10K. For the growth of In0.95Al0.05As nanostructures, dot formations are observed on the InAlAs and InGaAlAs buffer layers.

Effect of gravity on InGaSb crystal growth

The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of In0.1Ga0.9Sb crystal. Two parameters were considered: (1) the inclination angle (θ) of the sample for gravity as 0° and 53°, and (2) the sample diameter (D) as 9 mm and 5mm. When θ was 0°, the interface was almost flat, indicating that convection was axisymmetric and stable. Whereas the interface was distorted towards gravitational direction when θ was 53°, indicating that solutal convection was dominant. The decrease of growth temperature and sample diameter reduced the distortion of interface and the dissolution amount of GaSb feed. The homogeneous crystals were grown at the initial growth stage by supplying the GaSb component during growth.

Control of Order Parameter during Growth of In0.5Ga0.5P/GaAs Heterostructures by Gas Source Molecular Beam Epitaxy Using Tertiarybutylphosphine

For the <001>-oriented In0.5Ga0.5P/GaAs heterostructure grown by gas source molecular beam epitaxy (GSMBE) using tertiarybutylphosphine (TBP), presence of the natural ordering of group III atoms and its effect on heterointerface properties are investigated for the first time. Using in situ reflection high energy electron diffraction (RHEED) observation and photoluminescence (PL) measurements, growth temperature and growth sequence were optimized to grow high-quality InGaP layers with defect-free heterointerfaces. By PL measurements on <001>- and <311>-oriented samples simultaneously grown under the same growth conditions, existence of natural ordering in <001>-oriented samples was found. The so-called long-range order parameter, η, of the InGaP layer increased with increase of the TBP flow rate and with decrease of the growth rate. η could be changed in the range of 0.06–0.29 by changing the growth conditions, corresponding to the band gap change of 43 meV. The valence band offset (ΔEV) measured by in situ XPS method was 0.29 eV and was independent of the value of η. The change of conduction band offset (ΔEC) due to ordering caused a corresponding change in the sheet carrier density of two-dimensional electron gas at the heterointerface. No significant contribution from piezoelectric or spontaneous polarization was seen up to η=0.29.

In situ laser light scattering studies on the influence of kinetics on surface morphology during growth of In0.2Ga0.8As/GaAs

Using real-time in situ laser light scattering we study, in this work, the influence of growth kinetics on the initial development of the crosshatched morphology and its subsequent evolution. The crosshatched morphology is characteristic of relaxed low strained layers (ε&amp;lt; 2%) and has been traditionally related to the plastic relaxation process driven by generation and multiplication of dislocations. However we have observed that, if the growth rate is slow enough, the onset of crosshatch formation takes place at a layer thickness in which the dislocation formation and multiplication processes have not appeared yet. This reveals that the stress field generated by the small density of misfit dislocations formed by bending of the dislocations preexisting in the substrate is strong enough to affect the evolution of the growth front morphology. Our results also show that the starting point and evolution of this characteristic morphology depend on the growth rate in such a way that when the growth rate is lower the crosshatched morphology starts to develop at a smaller thickness and shows a faster evolution rate.

In-Situ Monitoring of In0.53Al0.13Ga0.34As/In0.52Al0.48As 1.55 µm Vertical Cavity Surface Emitting Laser Structure Grown by Metal Organic Chemical Vapor Deposition

A 1.55 µm vertical cavity surface emitting laser (VCSEL) structure was grown by low pressure metalorganic chemical vapor deposition method. In-situ laser reflectometry with a wavelength near resonant position of VCSEL structure was employed to monitor the optical thickness over the whole growth time. The distributed Bragg reflectors (DBR's) were grown with alternate In0.53Al0.13Ga0.34As and In0.52Al0.48As quarter lambda wavelength layers. The growth time of each layer in the DBR was determined through real time feedback of growth monitoring in the growth of In0.52Al0.48As and In0.53Al0.13Ga0.34As buffer layers prior to beginning the subsequently grown DBR structure. The oscillatory reflection signals by the laser operating at 1.53 µm gave information for the position of stop band in the reflectivity spectrum of the VCSEL structure. The reflectivity spectrum of VCSEL structure showed excellent square-shaped flat band wider than 50 nm where the reflectivity reached a plateau as expected by the in-situ monitoring data.