InGaAsP Alloys Research Articles

Enabling MOCVD production on next generation 150 mm Indium Phosphide wafer size

150 mm Indium Phosphide wafers are now commercially available with crystal quality comparable to wafer of smaller radius. This may pave the way for scaling up the production of a multitude of photonic devices for Datacoms operating in the 1.30-1.55μm infrared range with a gain in wafer surface of factor 4 and a reduction of roughly 50% in die cost. To achieve this goal, it is of utmost importance to prove that both AlGaInAs and InGaAsP quaternary compound semiconductors can be grown by metal–organic chemical vapor deposition (MOCVD) on wafers of larger sizes with both thickness and composition uniformities comparable to those achievable on 75 mm. In this article, we report pioneering production technology developments based on the Planetary Reactor® design. Both reactor and related inlet geometry have been deeply revisited with the introduction of a novel 4-fold injector, which in combination with Cl2 In-situ chamber clean, prove to enable such transition in wafer size. Sub-nanometric photoluminescence in-wafer uniformities are demonstrated and historic challenges, such as drift in material composition of highly sensitive InGaAsP alloys during a production campaign, are addressed thanks to this unique combination. Uniformity, tunability and reproducibility results are thus presented for two prototypical case scenarios: a highly strained AlGaInAs multiple quantum well (MQW) and a bulk InGaAsP layer with wavelength emission of 1550 nm and 1100 nm respectively to corroborate reactor flexibility in meeting industry requirements for next device generation.

P-GaAs/n-Ga2O3 heterojunction diode with breakdown voltage of ∼800 V

As an attractive next generation ultrawide bandgap material, Ga2O3 has been demonstrated to be capable of high voltage operation. However, the lack of shallow p-type dopant in Ga2O3 leads to difficulties in developing Ga2O3 based bipolar devices. The semiconductor grafting technology, by bonding a single crystalline p-type semiconductor nanomembrane (NM) to n-Ga2O3 to from abrupt heterojunction, offers a way to expand the application of Ga2O3 in bipolar areas. In this Letter, we report a p-GaAs/(001)-Ga2O3 heterojunction diode fabricated using semiconductor grafting technology. The single crystalline GaAs NM was prepared and transferred onto a Ga2O3 substrate, showing good integrity. Diodes of a mesa diameter of 25 μm were fabricated, showing a high breakdown voltage of ∼800 V, a power figure of merit of 126.5 MW/cm2, and a calculated 1D peak electric field of 1.60 MV/cm. The turn on voltage of the diode was determined to be around 1.91 V with an on–off ratio to be 6 × 106 at −4/4 V and the specific on resistance to be 5.06 mΩ cm2. The ideality factor was extracted to be approximately 1.34, indicating reasonable interface quality. The interfacial defects and the self-passivation effects of Ga2O3 are discussed, and the theoretical band diagram was analyzed for the p-GaAs/n-Ga2O3 heterojunction. By managing the peak electric field with suitable edge termination techniques, higher breakdown voltage can be expected. In addition, by taking advantage of the InGaAsP alloy system, a wide variety of GaAs-Ga2O3 based high voltage HBT can be further developed.

The discovery of the effect of compositional disorder on the opto-electronic properties of the deformed InGaAsP quaternary

This article presents a theoretical study of the optoelectronic properties of InGaAsP alloys fabricated on three different substrates: InP, GaA, and ZnSe. Particular attention has been paid to the study of bandgap energy along points of high symmetry in the Brillouin zone, absorption coefficient, and refractive index of materials without compositional disorder and subjected to deformation. Our goal is to expand the range of optoelectronic properties. We found that the absorption coefficient of the deformed InGaAsP/InP material in the absence of disorder varies between 9.66×104cm−1 and 1.35×105cm−1 changing the content of phosphorus and gallium, making it possible to provide a wide range of refractive indices [3.06, 3.84] compared to GaAs substrates [2.67, 3.02] and ZnSe [2.69, 3.05]. This refractive index contrast can be exploited in the design of optical waveguides.

Prediction of mechanical properties of In1-x GaxAsyP1-y lattice-matched to different substrates using artificial neural network (ANN)

ABSTRACT The mechanical properties, namely the elastic constants (C11, C12, and C44), bulk B, shear Cs, and Young’s modulus Y0, of the In1-xGaxAsyP1-y lattice-matched GaAs and InP substrates, were estimated using an artificial neural network (ANN method). This study aimed to create ANN networks that facilitate the estimation of the mechanical properties of alloys subjected to different temperatures and hydrostatic pressures. We aimed to predict the mechanical properties of InGaAsP alloys matched to InP and GaAs substrates as a function of temperature and hydrostatic pressure. ANN learning was performed based on the results validated by the empirical pseudopotential method data within the virtual crystal approximation, including the actual disorder potential. An ANN is a nonlinear process modeling technique frequently encountered in materials science. The predictive curves show high reliability, and underline the importance of using this approach to replace the time-consuming and costly experimental test, as well as to predict the mechanical response of the material where conventional modeling approaches have failed. Our method can consolidate the theoretical references found in the literature, it can also serve the field of engineering the mechanical properties of semiconductors, facilitate the successful design of optoelectronic devices, and serve future experimental works.

InP/InGaAsP thin films based solar cells: Lattice mismatch impact on efficiency

In this study, the optical proprieties and the performance of based indium gallium arsenide phosphide (InGaAsP) quaternary solar cells were investigated, the absorption and the bandgap energy of the InGaAsP quaternary epitaxy on the InP substrate were studied for different temperatures and pressure. Also, the lattice mismatch effect was introduced to investigate the change in the absorption coefficient and on the bandgap energy. We demonstrate that the physical parameters are more related to the variation of pressure than the temperature variation. An increase in absorption peaks is manifested by decreasing the pressure. This study allows us to explore the extrinsic conditions and the configuration of the deformations leading to the desired optoelectronic properties. Furthermore, the results found show that the rates of variation of the bandgap energy Eglh relating to the light holes, bandgap energy Eghh relating to the heavy holes, and of the bandgap energy Eg as a function of the pressure are more related to the rate of change of these energies as a function of temperature. The absorption coefficient α is important for materials with low bandgap energy, the peaks increase by increasing the temperature and by lowering the pressure. We exploited the results found to simulate a p-n junction cell based on the deformed InGaAsP alloy using the SCAPS software, we found that the deformation makes it possible to obtain a current Jsc equal to 47.03 mA/cm2, and it leads to a transition from the maximum current density to low voltages with conservation of its maximum value (36.03 mW/m2).

Ga originated kink-and-tail Zn diffusion profiles in InGaAsP and InGaAlAs alloys during MOVPE regrowth

We investigated the diffusion characteristics of Zn in ternary and quaternary alloys of InGaAsP and InGaAlAs, which are important materials in long-wavelength optical communication devices. The measured Zn diffusion profiles of InGaAs, InGaAsP, and InGaAlAs showed kink-and-tail shapes in which Zn concentration fell abruptly at first and then decreased slowly, whereas those of InP and InAlAs showed only abrupt decreases. Thus, only Ga-containing alloys had tail-like profiles. Since this tail was well described by the group-V vacancy related defect model, we deduced that its mechanism is closely related with group-V vacancies in Ga-related bonds such as GaP or GaAs. Furthermore, we demonstrated the possibility that many more group-V vacancies originated from GaP bonds than from GaAs bonds, indicating the difficulty in crystal growth of high quality alloys that have GaP components.

Enhancement of open circuit voltage in InGaAsP-inverted thin-film solar cells grown by solid-source molecular beam epitaxy

Because InGaAsP alloys grown on InP substrates with 1.05eV bandgap are often susceptible to compositional fluctuations owing to spinodal-like decomposition due to the miscibility gap, the corresponding open circuit voltage (VOC) for InGaAsP solar cells is typically smaller than the empirically expected value. In this study, we investigate the impact of the device structure on the VOC of In0.83Ga0.17As0.36P0.64 solar cells grown by solid-source molecular beam epitaxy. In comparison to the upright homojunction cell as a baseline, a reverse saturation current density (J0) for the upright heterojunction cell was effectively reduced from 3.2×10−4 to 1.5×10−6mA/cm2 using the n-InP emitter with higher electron mobility, resulting in an enhancement of VOC from 0.557 to 0.568V. Owing to the reduction of J0 to 2.8×10−7mA/cm2, the VOC was further enhanced to 0.590V for the inverted heterojunction cell. For the reduction of J0, a longer radiative lifetime of 20.2ns obtained for the inverted heterojunction cell by photoluminescence decay at room temperature, presumably caused by light trapping, was responsible. Consequently, the efficiency was enhanced from 9.5% for the upright homojunction cell to 12.1% for the inverted heterojunction cell. Using the inverted InGaAsP cell, we demonstrated the mechanically stacked InGaP/GaAs//inverted-InGaAsP (// denotes the bonded interface) triple-junction solar cells with enhanced VOC of 2.64V.

Low resistivity lateral P–I–N junction formed by Ni–InGaAsP alloy for carrier injection InGaAsP photonic devices

In this study, we investigate low-resistivity InGaAsP lateral P–I–N junctions using Ni–InGaAsP alloy in conjunction with Zn diffusion. It is found that Ni–InGaAsP alloy is formed via a direct reaction between Ni and InGaAsP after annealing at more than 300 °C. The Ni–InGaAsP preserves the initial Schottky junction properties between Ni and InGaAsP, and thus exhibits an ohmic contact for n-InGaAsP and a Schottky contact for p-InGaAsP. Hence, the Ni–InGaAsP alloy can be used instead of the Si ion implantation process to form the P–I–N junction. The Ni–InGaAsP alloy exhibits significantly lower contact resistance and sheet resistance than Si implanted n+-InGaAsP. The InGaAsP lateral P–I–N junction formed with the Ni–InGaAsP alloy and Zn diffusion shows approximately 10 times lower access resistance than the n+-InGaAsP junction. Thus, we successfully achieve large on-current in the lateral P–I–N junction with the Ni–InGaAsP alloy. The fabrication procedure of the lateral P–I–N junction using the Ni–InGaAsP alloy is promising for carrier-injection photonic devices on the III–V CMOS photonics platform.

Growth of InGaAsP Alloy Nanowires for Emission from Visible to Mid-Infrared Wavelengths

III-V compound semiconductor nanowires (NWs) have attracted considerable attention during the past decades as the building block of next generation of optoelectronic devices. Their tunable direct band gap, high carrier mobility and excellent mechanical properties make them superior candidates to other semiconductor materials (‎1). Having direct band gaps, most of the III-V NWs can be rationally designed and synthesized to cover a wide range of the band gap energy by tuning the composition. Full composition growth of InxGa1-xN on a single substrate covering the band gap from near UV to mid-IR was achieved for the first time through composition gradient of source materials by Kuykendall et al.(2). Recently we have been able to grow CdSSe and ZnCdSSe NWs alloys using dual gradient method (3,4). Even though alloy nanowires with tunable optical properties for visible wavelengths have received extensive attention, similar NWs for infrared applications have received much less attention. In this contribution, we present successful Au-catalyzed Vapor-Liquid-Solid (VLS) growth of InxGa1-xAs, GaxAs1-xP and InxGa1-xAsyP1-yNWs on a single substrate. Figure 1(a) is 2D composition plane demonstrating different paths for (In,Ga)(As,P) alloy systems. The four corners represent the four binaries, InAs, GaAs, InP, and GaP, while the four edges represent the corresponding four possible ternaries with varying composition, and each given (x,y) point in the interior represents a quaternary alloy of given composition. We report a chemical vapor deposition (CVD) of spatially composition-graded ternary and quaternary alloy semiconductor NWs based on (In,Ga)(As,P) material system with potential applications in optoelectronics, e.g. solar cells and photodetectors. Using the dual gradient method (DMG) we have achieved the continuous spatial composition gradient over a single substrate with a band gap spanning from InAs (0.35 eV) to GaP (2.26 eV) for different (In,Ga)(As,P) alloyed system. The current systematic study based on DMG growth methodology opens a new horizon on structural-optical study of different alloys in III-V systems for various optoelectronic device applications. Different alloys were grown on Si(111) coated with 2-3 nm Au film as catalyst for VLS growth. The growth time varies between 30-60 min for different samples, and also growth temperature was adjusted between 550-680◦C for various materials. For example, highly crystalline GaP is preferred to be grown at temperature around 600◦ C while GaAs around 650-680◦C. 40-45 sccm Ar+5%H2 was used as carrier gas and the pressure of the reactor was kept 1-10 Torr during the process. Based on the difference in enthalpy of formation for different binary materials, Au-coated substrate was positioned downstream facing the opening of the minitubes, each of which is loaded with different source materials. By tilting the substrate along the axial direction of hot-wall furnace tube it was possible to achieve spatially composition gradient growth of NWs over the single substrate. Figure 1(b) shows the representative SEM image of InGaAsP NWs grown on a Si(111) substrate. Optical properties of the as-grown NWs were investigated by photoluminescence (PL) measurements at room temperature using a Ti-Sapphire laser (810 nm) as an excitation source for NIR range and Nd-YLF (349 nm) for visible ranges. PL spectrum of InGaAs NWs shows a red shift from 1100 to 1900 nm from InAs to GaAs rich along the substrate (Fig 1(b)). NW size dependence on time evolution and temperature is also studied. Photoluminescence (PL) emission results agree with both EDS and XRD results on alloy compositions. M. Fang, N. Han, F Wang, Z. X. Yang, S. Yip, G. Dong, J. J. Hou, Y. Chuneh, and J. C. Ho, J. Nanomaterials 2014 (2014).T. Kuykendall, P. Ulrich, S. Aloni and P. Yang, Nature Materials 6, 951(2007) D. Caselli, Z. Liu, D. Shelhammer, and C.Z. Ning, Nano letters14(10), 5772 (2014)A. Pan , R. Liu , M. Sun, and C. Z. Ning, ACS Nano, 4 (2), 671 (2010) Figure 1

Performance Optimization of a Reconfigurable Waveguide Digital Optical Switch on InGaAsP–InP: Design, Material, and Carrier Dynamics

The design and performance of an InGaAsP-InP 1 times 2 reconfigurable waveguide digital optical switch (RW-DOS) actuated by carrier-induced refractive index modulation is described. Using a device model based on the two-dimensional beam propagation method, we present an analysis of the role of material bandgap, carrier lifetime, and waveguide design on the switch performance. The model results are compared with experimental measurements of carrier-induced index change and switching performance for RW-DOS devices and test structures fabricated in InGaAsP alloys with waveguide core compositions of Q = 1.2, Q = 1.3, and Q = 1.4 mum. We discuss compromises between power consumption, switching speed, and propagation loss. The optimized InGaAsP-InP devices exhibited better than 25-dB switching contrast ratio and require less than 20-mA drive current.

InP decomposition phosphorus beam source for MBE: design, properties and superlattice growth

The use of GaP and InP crystal decomposition for generating phosphorus molecular beam in MBE growth of multicomponent III-V alloys and multilayer heterostructures involving phosphorus is analysed. The operating characteristics of an InP decomposition phosphorus beam source are presented and MBE growth of InGaP and InGaAsP alloys with controlled composition in both sublattices is described. The usefulness of the source is further demonstrated by growing InGaP/InGaAsP short-period (8 nm) superlattices with high structural perfection as revealed by x-ray diffraction and transmission electron microscopy studies.

Investigation of carbon-doped base materials grown by CBE for Al-free InP HBTs

InGaAs/InP heterojunction bipolar transistors with a carbon-doped base are shown to have lower gain that those with a Be-doped base. In order to keep advantage of the low diffusivity of the carbon dopant, alternative carbon-doped materials have been tested as the base material. A quaternary InGaAsP alloy with a lower band gap than InGaAs to reduce Auger recombination proved to be unsatisfactory, because of low doping (<2×10 19 cm −3) and dramatically lower electron lifetime than in InGaAs. The compositionally graded base proved to be an attractive solution, allowing significantly improved gain in HBTs, and leading to some advantageous side effects, such as higher doping level, constant gain over large current range, and higher frequencies.

Structural and optical properties of 0.98 μm InGaAs/InGaAsP strained-compensated multiple quantum well structures grown by gas-source molecular beam epitaxy

The effects of growth temperature on the structural and optical properties of gas-source molecular beam epitaxy grown 0.98 μm InGaAs/InGaAsP strain-compensated multiple quantum well structures were studied by transmission electron microscopy (TEM), double crystal X-ray diffraction and photoluminescence measurements. It was found that high quality of quantum well structures can be obtained at a lower growth temperature. A higher growth temperature caused an immiscible growth for the InGaAsP alloy from the observation of the TEM images. As a result, the optical and structural quality of the quantum well structure was drastically degraded.

Ion implantation induced selective area exfoliation of InP and GaAs

Patterned exfoliation, driven by 0.45 MeV H and 1.0–1.4 MeV He implantations, has been demonstrated in single crystal GaAs and InP. In both materials implantation of 4 × 10 16 cm −2 He or 1 × 10 17 cm −2 H ions through a suitable implant mask, followed by a 350°C thermal anneal, resulted in expulsion of material exclusively from the implanted regions i.e. the exfoliation field mapped the details of the mask and in all cases to a depth determined by the depth of the implanted ion. The effect of varying the anneal temperature ramp-up rate is marked. At the highest rate so far examined (100°C/s) the expelled material from each exposed area can be in the form of a single block. Exfoliation is also demonstrated in InP containing a buried InGaAsP alloy layer.

Novel fabrication of C-doped base InGaAs/InP DHBT structures for high speed circuit applications

We have fabricated InGaAs/InP based DHBTs for high speed circuit applications. A process involving both wet chemical and ECR plasma etching was developed. Carbon was employed as the p-type dopant of the base layer for excellent device stability. Both the emitter–base and base–collector regions were graded using quaternary InGaAsP alloys. The extrinsic emitter–base junction is buried for junction passivation to improve device reliability. The use of an InP collector structure with the graded region results in high breakdown voltages of 8-10 V, with no current blocking. The entire structure is encapsulated with spin-on-glass. These devices show no degradation in d.c. characteristics after operation at an emitter current density of 90 kA cm −2 and a collector bias, V CE, of 2 V at room temperature for over 500 h. Typical common emitter current gain was 50. An f t of 80 and f max of 155 GHz were achieved for 2×4 μm 2 emitter size devices.

Ion-Beam-Milling of InGaAsP Alloys with N2/O2-Mixtures

In this paper ion-beam-milling of GaAs, InP as well as of InGaAs and InGaAsP of different compositions lattice-matched to InP was investigated using nitrogen and nitrogen/oxygen mixtures. The influence of process parameters such as gas composition, kinetic energy of the ions and the angle of incidence of the ions was investigated in detail. The etch rates of different masking materials like titanium, photoresist and SiO2 are also given. Special attention was paid to the geometry and roughness of the mesa facets in view of their use as laser facets. For the first time the experimental results are compared to calculations based on the sputter theory of Sigmund. The calculated dependence of the etch rates on the kinetic energy of the ions and on the angle of incidence up to 40° is in good agreement with the experimental results.

The role of strain and composition on the morphology of InGaAsP layers grown on 〈0 0 1〉InP substrates

A series of tensile or compressively strained InGaAsP alloys were grown by molecular beam epitaxy on 〈0 0 1〉InP substrates. The morphology and composition segregation of the films were assessed by transmission electron microscopy, using [1 1 0] and [1 1 0] cross-sections. Films grown under tension, whose compositions lay within the chemical spinodal, spontaneously faceted on {h h l} planes where lh = 3 or 4. All films grown under compression, as well as those grown under tension but lying outside the chemical spinodal, displayed a planar (0 0 1) growth. The wavelength of composition modulations, ≈ 10 nm, as determined by electron microscopy observations, scaled with the size of facets found in the first stages of growth. An analysis of the stress state in the films, accounting for the misfit between the film and substrate, the composition modulations and the faceting, was used to explain the synergy between composition and the stress state in promoting faceted growth.

LPE growth and characterization of InGaAsP/InP heterostructures: IR light-emitting diodes at 1.66 μm. Application to the remote monitoring of methane gas

Highly effective IR light-emitting diodes operating at the wavelength 1.66 μm and based on the buried heterostructure In 0.88Ga 0.12As 0.26P 0.74/ In 0.72Ga 0.28As 0.62P 0.38/In 0.53Ga 0.47As/InP have been grown by liquid-phase epitaxy (LPE) and characterized in detail by means of transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), electron diffraction (ED), X-ray diffraction (XRD), secondaryion mass spectrometry (SIMS) and electroluminescence measurements, The InGaAsP epilayers are found to be well lattice matched and of good structural quality. A tentative explanation is presented for the spinodal decomposition observed in InGaAsP alloys. A new type of selective CH4 gas sensor has been developed and fabricated on the basis of the IR light-emitting diode mentioned above. Especially designed for the remote control of CH 4 gas via fibre optics, an integrated optoelectronic readout scheme has been developed and tested. It is shown that the proposed type of sensor can be used for the quantitative remote control of CH 4 gas concentration (0.2-100%) via a fibre glass line up to a distance of 2 × 1 km.

Characterisation of the LPE grown InGaAsP/InP hetero-structures: IR-LED at 1.66 μm used for the remote monitoring of methane gas

Combined TEM, HREM, ED, SIMS, X-ray and electroluminescence studies were used to characterise in detail a highly effective IR-LED emitting at the wavelength 1.66 μm and based on buried heterostructure In0.88Ga0.12As0.26P0.74/In0.72Ga0.28As0.62P0.38/In0.53Ga0.47As/InP grown by liquid-phase epitaxy. The InGaAsP epilayers were found to be well lattice-matched, dislocation free and of good structural quality. A tentative explanation is presented for the spinodal decomposition observed in InGaAsP alloys. A new type of selective methane gas sensor has been developed and fabricated on the basis of the IR-light emitting diode mentioned above. It is shown that the proposed type of sensor can be used for the quantitative remote control of methane gas concentration (0.2–100%) via a fibre glass line up to the distance of 2 × 1 km.

1.26 W CW diffraction-limited InGaAsP flared amplifierat 780 nm

Flared amplifiers fabricated with InGaAsP alloys have produced 1.26 W CW at a wavelength of 780 nm in a single-lobed, diffraction-limited far field pattern. Under quasi-CW conditions, 2.4 W of diffraction-limited power has been obtained. This represents the highest diffraction-limited power reported at 780 nm and the highest diffraction-limited power reported in the InGaAsP material system.