Current-injected light emission of epitaxially grown InAs/InP quantum dots on directly bonded InP/Si substrate

Current-injected light emission was confirmed for metal organic vapor phase epitaxy (MOVPE) grown (Ga)InAs/InP quantum dots (QDs) on directly bonded InP/Si substrate. The InP/Si substrate was prepared by directly bonding of InP thin film and a Si substrate using a wet-etching and annealing process. A p–i–n LED structure including Stranski–Krastanov (Ga)InAs/InP QDs was grown by MOVPE on an InP/Si substrate. No debonding between Si substrate and InP layer was observed, even after MOVPE growth and operation of the device under continuous wave conditions at RT. The photoluminescence, current/voltage, and electroluminescence characteristics of the device grown on the InP/Si substrate were compared with reference grown on an InP substrate.

Source:IOPscience

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Photoluminescence assessment of undoped semi-insulating InP wafers obtained by annealing in iron phosphide vapour

We have investigated the photoluminescence mapping characteristics of semi-insulating (SI) InP wafers obtained by annealing in iron phosphide ambience (FeP2-annealed). Compared with as-grown Fe-doped and undoped SI InP wafers prepared by annealing in pure phosphorus vapour (P-annealed), the FeP2-annealed SI InP wafer has been found to exhibit a better photoluminescence uniformity. Radial Hall measurements also show that there is a better resistivity uniformity on the FeP2-annealed SI InP wafer. When comparing the distribution of deep levels between the annealed wafers measured by optical transient current spectroscopy, we find that the incorporation of iron atoms into the SI InP suppresses the formation of a few defects. The correlation observed in this study implies that annealing in iron phosphorus ambience makes Fe atoms diffuse uniformly and occupy the indium site in the SI InP lattice. As it stands, we believe that annealing undoped conductive InP in iron phosphide vapour is an effective means to obtain semi-insulating InP wafers with superior uniformity.

Source:IOPscience

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Crystalline Defects in InP-to-Silicon Direct Wafer Bonding

InP-to-Si wafer bonding has been proposed as a way of circumventing the problems associated with lattice-mismatch in heteroepitaxial growth. Therefore, in this study the dislocation density and material degradation in InP-to-Si hydrophobic bonding are evaluated. Both interface and InP bulk defects were studied using IR-transmission, atomic force microscopy (AFM) and defect-etching. When the bonded wafers were annealed below 300°C, no volume dislocations were generated in InP. However, when annealing above 300°C, the thermal mismatch stress induced large numbers of volume dislocations in InP. It was also shown that hydrophobic InP-to-Si wafer bonding unfortunately requires high-temperature annealing to achieve sufficient bonding-strength. However, a considerably lower dislocation density was observed in InP-to-Si wafer bonding than that in InP heteroepitaxial growth on Si. Also, when the samples were annealed above 400°C, asymmetric voids emerged at the interface. These voids are associated with the nucleation of indium droplets which causes microcavities at the interface where volume dislocations can sweep-out, forming surface steps. The voids completely disappeared when channel-patterned interfaces were used.

Source:IOPscience

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Room-temperature GaAs/InP wafer bonding with extremely low resistance

Low-temperature direct wafer bonding is a promising technique for fabricating multijunction solar cells with more than four junctions in order to obtain high conversion efficiencies. However, it has been difficult to reduce the bond interface resistance between a GaAs-based subcell wafer and an InP-based subcell wafer. We found that a novel bonding structure comprising heavily Zn-doped (1 ×1019 cm−3) p+-GaAs and S-doped (3 × 1018 cm−3) n-InP had an interface resistance of 2.5 × 10−5 Ωcm2, which is the lowest value ever reported. This result suggests that the newly developed room-temperature wafer bonding technique has high potential to realize high-efficiency multijunction solar cells.

Source:IOPscience

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