Articles you may be interested inStructural, morphological, and defect properties of metamorphic In0.7Ga0.3As/GaAs0.35Sb0.65 p-type tunnel field effect transistor structure grown by molecular beam epitaxy Material properties and performance of metamorphic optoelectronic integrated circuits grown by molecular beam epitaxy on GaAs substrates Metamorphic heterojunction bipolar transistor ͑M-HBT͒ structures and metamorphic P -I -N (M-PIN) photodiode structures were grown on GaAs substrates. A compositionally graded AlGaInAs buffer layer was used to expand the lattice constant to that of InP. Cross-sectional transmission electron micrographs of the M-HBT structure showed that the dislocations from compositional grading were predominantly localized in the buffer layer and that the device layers possessed planar interfaces. Secondary ion mass spectroscopy depth profiles of the 4ϫ10 19 cm Ϫ3 beryllium-doped In 0.53 Ga 0.47 As base layer exhibited sharp doping interfaces, indicating that metamorphic growth was not causing enhanced beryllium diffusion. The current gain of large emitter M-HBT devices approached the current gain for the same device structure grown on an InP substrate. A P -I -N photodiode structure was also grown metamorphically on a GaAs substrate and lattice matched on an InP substrate. Both types of photodiodes showed almost identical responsivities and bandwidths. A responsivity to 1.55 m radiation of 0.55 A/W, which corresponds to an external quantum efficiency of 44%, was obtained with M-PIN photodiodes. The 3 dB bandwidths exceeded 20 GHz for M-PIN photodiodes with diameters of 25 m or smaller. These results are very encouraging for the application of metamorphic technology to nonmajority carrier devices.

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Articles you may be interested inRole of InAs and GaAs terminated heterointerfaces at source/channel on the mixed As-Sb staggered gap tunnel field effect transistor structures grown by molecular beam epitaxy Molecular beam epitaxial growth of InAs/AlGaAsSb deep quantum well structures on GaAs substrates A novel metamorphic high electron mobility transistor ͑HEMT͒ structure was grown on GaAs substrates by solid-source molecular-beam epitaxy for potential microwave power applications. The HEMT device layers were strain compensated with pseudomorphic ͑tensile-strained͒ Al 0.3 In 0.7 P donor-barrier layers and a pseudomorphic ͑compressive-strained͒ InP channel layer. Atomic force microscopy measurements of the metamorphic structure yielded a root-mean-square surface roughness of 8 Å. Transmission electron micrographs of the device layers exhibited flat interfaces with the dislocation density estimated to be less than 1ϫ10 6 cm Ϫ2 . Room temperature photoluminescence measurements of metamorphic AlInP layers indicated large direct band gaps up to 2.10 eV. Due to the larger conduction band discontinuity at the Al 0.3 In 0.7 P/InP heterojunction than the AlGaAs/InGaAs heterojunction in GaAs pseudomorphic HEMTs, significantly higher channel sheet densities were obtained. For Al 0.3 In 0.7 P/InP HEMTs, channel sheet densities ͑cm Ϫ2 ͒ exceeding 3ϫ10 12 for single-pulse-doped, and greater than 4ϫ10 12 for double-pulse-doped, structures were readily obtained. Hall measurements on a double-pulse-doped Al 0.3 In 0.7 P/InP/Al 0.3 In 0.7 P HEMT gave mobilities ͑cm 2 /V s͒ of 4450 at 300 K and 18 500 at 77 K, which are consistent with a high quality InP channel layer. Secondary ion mass spectroscopy depth profiles of a double-pulse-doped structure displayed sharp doping pulses and interfaces indicating that metamorphic growth was not leading to enhanced diffusion or migration. Initial and nonoptimized devices with a gate length of 0.15 m exhibited a maximum current density of 500 mA/mm and a transconductance of 520 mS/mm, which compare favorably to mature AlGaAs/InGaAs pseudomorphic HEMTs.

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