Growth Of GaSb Research Articles

Growth and Dark Current Analysis of GaSb- and InP-Based Metamorphic In0.8Ga0.2As Photodetectors.

Short-wavelength infrared photodetectors based on metamorphic InGaAs grown on GaSb substrates and InP substrates are demonstrated. The devices have a pBn structure that employs an AlGaAsSb thin layer as the electron barrier to suppress dark current density. The strain effect on the electrical performance of the devices was specifically studied through the growth of the pBn structure on different substrates, e.g., InP and GaSb, via a specific buffering technique to optimize material properties and minimize dark current. A lower device dark current density, down to 1 × 10-2 A/cm2 at room temperature (295 K), was achieved for the devices grown on the GaSb substrate compared to that of the devices on the InP substrate (8.6 × 10-2 A/cm2). The improved properties of the high-In component InGaAs layer and the AlGaAsSb electron barrier give rise to the low dark current of the photodetector device.

Temperature dynamic compensation vertical Bridgman method growth of high-quality GaSb single crystals

Gallium antimonide (GaSb) is considered an ideal substrate for heterostructure growth. A significant property that inhibits the widespread application of infrared plane-array detector growth on GaSb is the crystal quality of the starting substrate. Herein, we report the growth of single-crystal GaSb by a temperature dynamic compensation vertical Bridgman (TDC-VB) method. This approach offers a low temperature gradient and a stable solid–liquid interface position in the furnace during the growth process. Two inch diameter twin-free GaSb single crystals with (100) orientation have been reproducibly obtained using the TDC-VB method. The crystalline character of the obtained GaSb has been examined by optical microscopy (OM), high-resolution X-ray diffraction (HRXRD), X-ray tomography (XRT), and Fourier-transform infrared (FTIR) spectroscopy. The etch pit dislocation density (EPD) of the GaSb polished wafers (100) was 6–72 cm−2, and the full-width at half-maximum (FWHM) of the Bragg diffraction peak was 15.4″. A uniform XRT image was obtained, and ca. 50 % of the GaSb wafers, which were produced by one crystal, showed transmittance > 20 % at 10 µm, indicating the formation of high-quality GaSb crystals. This work provides useful guidelines for the formation of high-quality GaSb crystals with significant promise for substrate applications.

Facile surface treatment of precursors before rapid melt growth of GaSb on silicon

The efficient monolithic III-V integration on silicon (Si) substrates can leverage the excellent optoelectronic properties of III-V semiconductors and the Si microfabrication technology for electronic, optoelectronics, integrated photonics devices. However, the origin of the interfacial and material defects during III-V monolithic integration on Si poses the challenge to achieve efficient optical emitters, detectors. In this study, we investigated different surface treatment schemes before rapid melt growth (RMG) of GaSb on Si substrate to attain defect control. The deposition of an Sb layer (10 nm) on GaSb precursors surfaces resulted in achieving better structural and optical properties of GaSb post RMG. We achieved a reduction of 2.48 atomic % of unintentional incorporation of Si into the GaSb via Sb treatment compared to that of untreated GaSb analysed using transmission electron microscopy and energy-dispersive X-ray spectroscopy. Improved surface morphology with reduced root mean square roughness of 3.7 nm is obtained with Sb layer treatment compared to 5.6 nm for untreated GaSb precursor measured by atomic force microscopy. We obtained improved optical properties and low defect density with an in-situ Sb treatment scheme on GaSb precursor surface by µ-Photoluminescence and µ-Raman spectroscopy analysis.

Monolayer oscillations of the Sb desorption rate during molecular beam epitaxy of GaSb

In-situ desorption mass spectrometry (DMS) tool is used to report monolayer oscillations of the Sb desorption rate during molecular beam epitaxy (MBE) growth of GaSb and GaInSb. Oscillations in the Sb desorption rate appear to be correlated to the variation in the surface-step-density that periodically changes the additional uptake and expulsion of Sb beyond the fixed rate of consumption. This notion is corroborated by comparing the Sb DMS signal to the time derivative of the specular RHEED beam intensity.

Effects of Bi Irradiation on the Molecular Beam Epitaxy Growth of GaSb on Ge (111) Vicinal Substrates

The growth of GaSb on Ge (111) vicinal substrates is performed by molecular beam epitaxy with Bi irradiation previous to and during the growth. The effects of the Bi irradiation on the surface morphology and on the crystallinity are investigated using atomic force microscopy and X‐ray diffraction, respectively. It is shown that Bi works as a surfactant, which suppresses the generation of rotational twins in the GaSb layer.

Structural analysis and resistivity measurements of InAs and GaSb fins on 300 mm Si for vertical (T)FET

We report on the uniform selective area growth of InAs and GaSb by metal-organic vapor phase epitaxy on a patterned shallow trench isolation SiO2/Si 300 mm template. High-quality InAs fins are realized via direct InAs nucleation on Si in the trenches. 60° interfacial misfit dislocation arrays formed along the {111} oriented InAs/Si interfaces accommodate most of the lattice mismatch such that threading dislocation generation from residual strain is minimized. GaSb grown on a thick GaAs buffer (partial filling of the trench) suffers from twin formation. The twin density is found to decrease with increasing growth temperature. To maximize the volume of low-defect density material inside the trench, the GaSb growth is initiated as close as possible to the trench bottom. Therefore, uniform high-quality GaSb fins are grown on a very thin low-temperature GaAs and the newly developed InAs seed in the V-groove. High-resolution x-ray diffraction reciprocal space maps show that the InAs and GaSb fins are nearly completely relaxed. The resistivity of undoped and n-doped InAs and undoped and p-doped GaSb fins is measured on as-grown material by micro-4-point-probe without the need for additional complicated device processing. The values are compared to those required for devices as presented in modeling papers. The result is encouraging for the ultra-large-scale integration of vertical nanowire III-V (tunnel) field-effect transistor on 300 mm Si.

Crystal structure control of Au-free InAs and InAs/GaSb heterostucture nanowires grown on Si (111) by metal-organic chemical vapor deposition

In this letter, the growth of gold-free GaSb on various InAs nanowire (NW) crystal structures using metal-organic chemical vapor deposition is demonstrated. The GaSb was grown radially and axially on wurtzite (WZ), zinc-blend (ZB) and polytype (mixture of WZ and ZB) InAs NWs. The effect of the various InAs crystal structures on GaSb was studied. This study demonstrates the control of the crystal growth of InAs and InAs/GaSb heterostructure NWs through the optimization of growth parameters and crystal transfer from core to shell, such techniques are necessary for the growth of NWs for future nanoelectronic device applications, such as TFET.

GaSb/GaAlAsSb Heterostructure Photodiodes for the Near-IR Spectral Range

GaSb/GaAlAsSb uncooled photodiodes for the 1.1–1.85 μm spectral range are fabricated and studied. A unique method for the growth of GaSb from lead solution-melts makes it possible to obtain a low carrier concentration in the active region: n = 2 × 1015 cm–3. The capacitance of the photodiodes is 70–110 pF for a sensitive -area diameter of 300 μm and 150–250 pF for a diameter of 500 μm. The photodiodes are characterized by a high (for GaSb devices) spectral sensitivity Sλ = 0.95 A/W at the maximum, a relatively low reverse dark current density j = (4–9) × 10–3 A/cm2 at Urev = 1.0–2.0 V, and high-speed performance (response time 5–10 ns).

Growth and characterization of an InSb infrared photoconductor on Si via an AlSb/GaSb buffer

A 99.6% relaxed InSb layer is grown on a 6° offcut (1 0 0) Si substrate via an AlSb/GaSb buffer using molecular beam epitaxy (MBE). A 200 nm GaSb buffer is first grown on Si and the lattice mismatch between them is accommodated by an interfacial misfit (IMF) array consisting of uniformly distributed 90° misfit dislocations. Si delta doping is introduced during the growth of GaSb to reduce the density of threading dislocation. Subsequently, a 50 nm AlSb buffer is grown followed by a 0.8 µm InSb layer. The InSb layer exhibits a 300 K electron mobility of 22,300 cm2/Vs. An InSb photoconductor on Si is demonstrated with a photoconductive gain from 77 K to 200 K under a 700 °C maintained blackbody.

Growth and characterization of InSb on (1 0 0) Si for mid-infrared application

Monolithic integration of InSb on (100) Si is a practical approach to realizing on-chip mid-infrared photonic devices. An InSb layer was grown on a (100) Si substrate using an AlSb/GaSb buffer containing InSb quantum dots (QDs). The growth process for the buffer involved the growth of GaSb on Si using an interfacial misfit array, followed by InSb QDs on AlSb to decrease the density of microtwins. InSb layers were separately grown on AlSb and GaSb surfaces to compare the effect of different interfacial misfit arrays. The samples were characterized using transmission electron microscopy and X-ray diffraction to determine the structural properties of the buffer and InSb layers. The InSb on the AlSb sample exhibited higher crystal quality than the InSb on GaSb sample due to a more favorable arrangement of interfacial misfit dislocations. Hall measurements of unintentionally doped InSb layers demonstrated a higher carrier mobility in the InSb on the AlSb sample than in InSb on GaSb. Growing InSb on AlSb also improved the photoresponsivity of InSb as a photoconductor on Si.

Фотодиоды для ближней инфракрасной области спектра на основе GaSb/GaAlAsSb-гетероструктур

AbstractGaSb/GaAlAsSb uncooled photodiodes for the 1 . 1–1 . 85 μm spectral range are fabricated and studied. A unique method for the growth of GaSb from lead solution-melts makes it possible to obtain a low carrier concentration in the active region: n = 2 × 10^15 cm^–3. The capacitance of the photodiodes is 70–110 pF for a sensitive -area diameter of 300 μm and 150–250 pF for a diameter of 500 μm. The photodiodes are characterized by a high (for GaSb devices) spectral sensitivity S _λ = 0 . 95 A/W at the maximum, a relatively low reverse dark current density j = (4–9) × 10^–3 A/cm^2 at U _rev = 1 . 0–2 . 0 V, and high-speed performance (response time 5–10 ns).

GaSb solar cells grown on GaAs via interfacial misfit arrays for use in the III-Sb multi-junction cell

Growth of GaSb with low threading dislocation density directly on GaAs may be possible with the strategic strain relaxation of interfacial misfit arrays. This creates an opportunity for a multi-junction solar cell with access to a wide range of well-developed direct bandgap materials. Multi-junction cells with a single layer of GaSb/GaAs interfacial misfit arrays could achieve higher efficiency than state-of-the-art inverted metamorphic multi-junction cells while forgoing the need for costly compositionally graded buffer layers. To develop this technology, GaSb single junction cells were grown via molecular beam epitaxy on both GaSb and GaAs substrates to compare homoepitaxial and heteroepitaxial GaSb device results. The GaSb-on-GaSb cell had an AM1.5g efficiency of 5.5% and a 44-sun AM1.5d efficiency of 8.9%. The GaSb-on-GaAs cell was 1.0% efficient under AM1.5g and 4.5% at 44 suns. The lower performance of the heteroepitaxial cell was due to low minority carrier Shockley-Read-Hall lifetimes and bulk shunting caused by defects related to the mismatched growth. A physics-based device simulator was used to create an inverted triple-junction GaInP/GaAs/GaSb model. The model predicted that, with current GaSb-on-GaAs material quality, the not-current-matched, proof-of-concept cell would provide 0.5% absolute efficiency gain over a tandem GaInP/GaAs cell at 1 sun and 2.5% gain at 44 suns, indicating that the effectiveness of the GaSb junction was a function of concentration.

Epitaxial growth of GaSb on V-grooved Si (001) substrates with an ultrathin GaAs stress relaxing layer

We report epitaxial growth of GaSb nano-ridge structures and planar thin films on V-groove patterned Si (001) substrates by leveraging the aspect ratio trapping technique. GaSb was deposited on {111} Si facets of the V-shaped trenches using metal-organic chemical vapor deposition with a 7 nm GaAs growth initiation layer. Transmission electron microscopy analysis reveals the critical role of the GaAs layer in providing a U-shaped surface for subsequent GaSb epitaxy. A network of misfit dislocations was uncovered at the GaSb/GaAs hetero-interface. We studied the evolution of the lattice relaxation as the growth progresses from closely pitched GaSb ridges to coalesced thin films using x-ray diffraction. The omega rocking curve full-width-at-half-maximum of the resultant GaSb thin film is among the lowest values reported by molecular beam epitaxy, substantiating the effectiveness of the defect necking mechanism. These results thus present promising opportunities for the heterogeneous integration of devices based on 6.1 Å family compound semiconductors.

Suppression of twin generation in the growth of GaAs on Ge (111) substrates

The generation of rotational twins in the growth of GaAs and GaSb on Ge(111) substrates by molecular beam epitaxy has been characterized by X-ray diffraction. Rotational twins are shown to be less generated in GaSb than in GaAs. It has been demonstrated that the generation of rotational twins in GaAs can be suppressed by inserting GaSb as a buffer layer. It has also been demonstrated that the use of the As2 beam and vicinal surfaces is effective for suppressing twin generation in GaAs.

Selective area heteroepitaxy of GaSb on GaAs (001) for in-plane InAs nanowire achievement

The growth of in-plane GaSb nanotemplates on a GaAs (001) substrate is demonstrated combining nanoscale patterning of the substrate and selective area heteroepitaxy. The selective growth of GaSb inside nano-stripe openings in a SiO2 mask layer is achieved at low temperature thanks to the use of an atomic hydrogen flux during the molecular beam epitaxy. These growth conditions promote the spreading of GaSb inside the apertures and lattice mismatch accommodation via the formation of a regular array of misfit dislocations at the interface between GaSb and GaAs. We highlight the impact of the nano-stripe orientation as well as the role of the Sb/Ga flux ratio on the strain relaxation of GaSb along the [110] direction and on the nanowire length along the [1-10] one. Finally we demonstrate how these GaSb nanotemplates can be used as pedestals for subsequent growth of in-plane InAs nanowires.

Epitaxial growth of GaSb and InAs fins on 300 mm Si (001) by aspect ratio trapping

We report on the monolithic integration of GaSb and InAs fins on on-axis 300 mm Si (001) by metal-organic chemical vapor deposition. The thickness of the GaAs/Si (001) fins used as a template is optimized to allow the formation of {111} facets and the confinement of defects generated at the GaAs/GaSb and GaAs/InAs interfaces by means of the aspect ratio trapping technique. Anti-phase domains are avoided via a careful design of the GaAs/Si interface. Threading dislocations in GaSb are controlled through the formation of an interfacial misfit dislocation array along the GaSb/GaAs [1¯11] and [11¯1] interfaces. Defects on InAs are controlled through the promotion of a two-dimensional growth, which spontaneously occurs on GaAs {111} planes. The results represent a step forward towards the integration of III–V nano-scale photonic and electronic components on a Si complementary metal-oxide-semiconductor compatible platform using a precisely engineered GaAs on Si template.

Demonstration of Sn-seeded GaSb homo- and GaAs–GaSb heterostructural nanowires

The particle-assisted epitaxial growth of antimonide-based nanowires has mainly been realized using gold as the seed material. However, the Au-seeded epitaxial growth of antimonide-based nanowires such as GaSb nanowires presents several challenges such as for example direct nucleation issues and crystal structure tuning. Therefore, it is of great importance to understand the role of seed material choice and properties in the growth behavior of antimonide-based nanowires to obtain a deeper understanding and a better control on their formation processes. In this report, we have investigated the epitaxial growth of GaSb and GaAs–GaSb nanowires using in situ-formed tin seeds by means of metalorganic vapor phase epitaxy technique. This comprehensive report covers the growth of in situ-formed tin seeds and Sn-seeded GaSb nanowires on both GaAs and GaSb (111)B substrates, as well as GaAs–GaSb nanowires on GaAs (111)B substrates. The growth behavior and structural properties of the obtained GaSb nanowires are further investigated and compared with the Au-seeded counterparts. The results provided by this study demonstrate that Sn is a promising seed material for the growth of GaSb nanowires.

GaSb and InSb Quantum Nanostructures: Morphologies and Optical Properties

ABSTRACTGaSb/GaAs and InSb/GaAs material systems can create type-II quantum nanostructures which provide interesting electronic and optical properties such as having long carrier life time, low carriers-recombination rate, and emitting/absorbing low photon energy. These characteristics of type-II nanostructures can be applied for infrared or gas detection devices, for memory devices and even for novel intermediate band solar cells. In contrast, lattice mismatches of GaSb/GaAs and InSb/GaAs material system are 7.8% and 14.6%, respectively, which need some specific molecular beam epitaxial (MBE) growth conditions for quantum nanostructure formation via Stranski–Krastanov growth mode.In this paper, the growth of self-assembled GaSb and InSb quantum nanostructures on (001) GaAs substrate by using MBE was reported. The surface morphology of these two quantum nanostructures and their optical properties were characterized by atomic force microscopy and photoluminescence (PL). The experimental results were compared between these two quantum nanostructures. Due to the lattice mismatch in each material system and the difference in sticking coefficient of Ga- and In-atoms during epitaxial growth, we obtain GaSb/GaAs quantum dots (QDs) with a density ∼1010 dots/cm2 and InSb/GaAs QDs with a density of ∼108 dots/cm2. The facet analysis of individual quantum nanostructure in each material system reveals that GaSb/GaAs QD has a dome-like shape with nearly isotropic property while InSb QDs form a rectangular-like shape with elongation along [110]-direction showing a strong anisotropic property.Low temperature PL spectra from capped GaSb and InSb quantum nanostructures show the energy peaks at 1.08-1.11 and 1.16-1.17 eV, respectively. The variations of PL peaks as a function of both temperature and excitation power are investigated. PL peak shows clear blue shift when excitation power is increased. This work manifests a possibility to use both GaSb and InSb quantum nanostructures for nanoelectronic and nanophotonic applications.

Heterointegration of III–V on silicon using a crystalline oxide buffer layer

The integration of III–V compound semiconductors with Si can combine the cost advantage and maturity of Si technology with the superior performance of III–V materials. We have achieved the heteroepitaxial growth of III–V compound semiconductors on a crystalline SrTiO3 buffer layer grown on Si(001) substrates. A two-step growth process utilizing a high temperature nucleation layer of GaAs, followed by a low-temperature GaAs layer at a higher growth rate was employed to achieve highly crystalline thick GaAs layers on the SrTiO3/Si substrates with low surface roughness as seen by AFM. The effect of the GaAs nucleation layer on different surface terminations for the SrTiO3 layer was studied for both on axis and miscut wafers, which led to the conclusion that the Sr terminated surface on miscut substrates provides the best GaAs films. Using GaAs/STO/Si as virtual substrates, we have optimized the growth of high quality GaSb using the interfacial misfit (IMF) dislocation array technique. This work can lead to the possibility of realizing infrared detectors and next-generation high mobility III–V CMOS within the existing Si substrate infrastructure.

Growth of high-homogeneity GaSb:Te crystals for thermophotovoltaic energy converters

Problems concerning the technology of growing highly homogeneous semiconductor crystals are discussed. The dependence between the inhomogeneity of GaSb:Te substrates and the efficiency of thermophotovoltaic converters (TPVCs) fabricated on their base via the diffusion technique is examined. The macro- and microhomogeneities of grown crystals can be substantially increased on account of the theoretically substantiated and experimentally implemented approximation to diffusive mass transfer conditions in the melt. The characteristics of TPVCs on substrates made of crystals with the most homogeneous properties exceed the analogous characteristics of other samples.