Combined (200) DF-TEM and X-ray diffraction investigations of interfaces in MOVPE grown InGaP/GaAs heterojunctions (original) (raw)
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Defect study of MOVPE-grown InGaP layers on GaAs
Journal of Crystal Growth, 2004
MOVPE-grown n-type GaAs/InGaP/GaAs structures with different GaAs cap layer thicknesses were studied by deep-level transient spectroscopy. An electron trap E1 with a thermal activation energy of 0.75 eV is formed in lattice matched InGaP after the MOVPE growth, if is not capped by sufficiently thick GaAs. The lattice mismatch of the InGaP layer influences the thermal activation energy of the deep defect, but not its occurrence or concentration. The starting surface concentration of the deep level defect as well as its diffusion at room temperature into the InGaP are apparently promoted by intrinsic defects in the InGaP layer determined by its growth condition. The shape of the depth profiles suggests that an extrinsic defect moves via interstitial sites into empty substitutional sites of the InGaP lattice. Oxygen atoms on phosphorus sites are probable candidates for the E1-related defects. r
Characterization of InGaP/GaAs heterointerfaces grown by metal organic vapour phase epitaxy
Journal of Crystal Growth, 2000
In GaAs/InGaP/GaAs structures grown by metal organic vapor-phase epitaxy (MOVPE), the two heterointerfaces are not identical. Normal photoluminescence (PL) features corresponding to the band gaps of GaAs and InGaP are seen for InGaP layer grown on GaAs. However, an intense long-wavelength feature is observed if we grow GaAs on InGaP (inverted structure) while the features of InGaP and GaAs are suppressed. The nature of interfacial regions is investigated by using di!erent gas switching sequences, which can in#uence the interfacial region composition. Signi"cantly, we "nd anomalous PL features similar to those observed in the case of inverted structure if we brie#y interrupt the growth of InGaP on GaAs and introduce AsH during the growth interruption. Secondary-ion mass spectrometry (SIMS) measurements and preliminary results of the compositional analysis of the interfacial layers based on high resolution X-ray di!raction (HRXRD) and PL measurements suggest that a deleterious e!ect arises with the exposure of InGaP surface to AsH and is attributed to the formation of an interfacial InGaAsP layer.
Journal of Crystal Growth, 2000
Metal-semiconductor contacts are used to examine the depth-resolved electrical characteristics of Si-and Zn-doped GaAs/(In,Ga)P/GaAs heterojunctions by capacitance}voltage measurements and deep-level transient Fourier spectroscopy. The experimental depth pro"les of the carrier concentration are compared with calculations based on selfconsistent solutions of the Poisson equation. By varying the growth conditions, heterointerfaces of GaAs with disordered or double-and single-variant ordered (In,Ga)P layers are produced. It is shown that normal [(In,Ga)P-on-GaAs] and inverted [GaAs-on-(In,Ga)P] interfaces are not equivalent with respect to their electrical properties. For the inverted Si-doped heterointerface, the depth pro"les of the electron concentration strongly depend on the growth conditions. In spite of a large carrier de"cit at this interface, the density of interfacial traps in the upper half of the bandgap is found to be low in the 10 cm\ range. For interfaces with disordered (In,Ga)P, the conduction and valence band o!sets are independently determined to be 0.20 and 0.27 eV, respectively. These heterointerfaces exhibit type-I character, in agreement with theoretical predictions. For interfaces with single-variant ordered (In,Ga)P, the conduction band discontinuity is found to be also 0.20 eV, in contrast to calculations of the band alignment for ordered (In,Ga)P, which predict !0.13 eV.
Atomic diffusion and interface electronic structure at In 0.49 Ga 0.51 P/GaAs heterojunctions
We have performed cross-sectional cathodoluminescence spectroscopy and secondary ion mass spectrometry measurements of lattice-matched, SiO x -capped In 0.49 Ga 0.51 P / GaAs double heterostructures ͑DHs͒ in order to investigate the relation between chemical interactions and localized electronic states at the epitaxial heterojunction. We measure atomic diffusion of over 100 nm resulting from anneals ranging from 650 to 850°C. A 20 meV increase in the near-band-edge ͑NBE͒ emission energy of InGaP is observed after the highest temperature anneals. This increase is consistent with an increase in the Ga concentration of the ternary layer as a result of diffusion from neighboring GaAs layers. Additionally, we observe InGaP / GaAs interface-localized features at ϳ1.49 and ϳ1.37 eV. The intensity of these emissions relative to the band-edge emission of the underlying layer depends sensitively on the anneal temperature and corresponding diffusion. These results reveal a correlation between cross diffusion and defect emission at InGaP / GaAs interfaces. They clarify the nature of the cross diffusion and reactions that occur at these interfaces in SiO x -capped structures, and those may be expected to occur during interface growth or processing at elevated temperatures. It is demonstrated that these chemical effects can have a significant impact on the electronic structure of lattice-matched III-V heterostructures.
Thermodynamical analysis of abrupt interfaces of InGaP/GaAs and GaAs/InGaP heterostructures
2005
Interfaces between arsenide and phosphide III-V semiconductors have shown to be one of the most difficult issues to be understood and definitively solved. This problem is particularly relevant with Vapour Phase Epitaxy (VPE) and Metallo-Organic Vapour Phase Epitaxy (MOVPE) techniques, since an irreproducibility in preparing abrupt interfaces between arsenide and phosphide has been evidenced. Several researchers have ascribed this problem to the volatility of arsenic and phosphorus species and since then for long time different recipes and growth procedures have been suggested in order to obtain sharp transition between the two different materials. In this work the film/substrate interface is modelled using thermodynamical calculations after the regular solution model proposed by Jordan and Ilegems: PH 3 flows over GaAs surface, and as a consequence the substrate is enriched with P, with the formation of a thin layer of GaAsP and mixed AsP gaseous species. Samples of InGaP on GaAs substrate were grown by MOVPE and characterised by Secondary Ion Mass Spectroscopy (SIMS) and Transmission Electron Microscopy (TEM) in order to support the theoretical findings.
Structural investigation of MOVPE-grown GaAs on Ge by x-ray techniques
The selection of appropriate characterization methodologies is vital for analyzing and comprehending the sources of defects and their influence on the properties of heteroepitaxially grown III-V layers. In this work, we investigate the structural properties of GaAs layers grown by metal-organic vapour phase epitaxy on Ge substrates-(1 0 0) with 6 • offset towards 1 1 1 -under various growth conditions. Synchrotron x-ray topography is employed to investigate the nature of extended linear defects formed in GaAs epilayers. Other x-ray techniques, such as reciprocal space mapping and triple axis ω-scans of (0 0 l)-reflections (l = 2, 4, 6), are used to quantify the degree of relaxation and presence of antiphase domains (APDs) in the GaAs crystals. The surface roughness is found to be closely related to the size of APDs formed at the GaAs/Ge heterointerface, as confirmed by x-ray diffraction (XRD), as well as atomic force microscopy and transmission electron microscopy.
Journal of Applied Physics, 1996
We present a study of the relaxation behavior of compressive In x Ga 1Ϫx P layers grown by atomic layer molecular-beam epitaxy at T s ϭ420°C with xϭ56%Ϯ3% and xϭ67%Ϯ3%. Similar ͑thickness and composition͒ In x Ga 1Ϫx P layers were grown under different growth conditions in order to assess the influence of the stoichiometry of the growth front on the structural properties and the relaxation process of this material system. All In x Ga 1Ϫx P layers were characterized by double-crystal x-ray diffraction, transmission electron microscopy, and Nomarski interference. Our results show that surface stoichiometry during growth does not affect the relaxation behavior of In x Ga 1Ϫx P layers but strongly determines their structural characteristics related to composition modulation features which appear in all our In x Ga 1Ϫx P layers. We have established an empirical relation between residual strain and thickness. This relation makes predictable the residual strain of more complicated structures which can be introduced as buffer layers in lattice-mismatched heteroepitaxial systems.
The morphology of an InP wetting layer on GaAs
Applied Surface Science, 2004
The effects of material intermixing, group V atom desorption and exchange on the surface morphology of InP wetting layers on GaAs substrates were studied by varying the growth temperature and coverage in metalorganic vapor phase epitaxy. Tertiarybutylphosphine (TBP) was used as the phosphorus source and the surface morphology was characterized by atomic force microscopy. The observations showed that the morphology depends strongly on the growth parameters and deteriorates with increasing temperature and decreasing InP coverage. It was verified that the main reason for the morphology impairment is the strongly temperature dependent group V atom exchange and desorption within several monolayers on the sample surface during exposures of the GaAs surface to TBP. However, a smooth morphology could be obtained within a wide temperature range by depositing at least a complete monolayer of InP. #
Optical characterization of MOVPE grown -InAs layers in GaAs
Physica Status Solidi (c), 2005
Optical properties of various MOVPE grown structures containing InAs δ-layers in GaAs were investigated by photoluminescence, photocurrent and photomodulated reflectance spectroscopy. Observed ground and high-order interband transitions were interpreted by simulation of electronic states in InAs δ-layers using the theoretical model accounting for influence of stress and quantum states coupling. It is shown, that material parameters crucial for optimization and growth control of InAs δ-layers structures, such as equivalent layer thicknesses/compositions, can be extracted from obtained optical data. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct MOVPE growth of InP on GaAs substrates
Journal of Crystal Growth, 1988
We have been able to develop a new useful method for the heteroepitaxial growth on a highly lattice-mismatched substrate by MOVPE successfully. We have found that the surface morphology of InP epitaxial layer grown on a GaAs substrate by MOVPE strongly depends on the supply rate of the group III material. Based on this experimental finding, an lnP epitaxial layer with a uniform and mirror.smooth surface has been successfully grown on a 2-inch GaAs (100) substrate. In addition to the surface morphology, we have measured the RHEED pattern, the x-ray diffraction pattern, the Hall mobility, the carrier concentration, and the photolurninescence as functions of the flow rate of the group 1II carrier gas.