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Notes: A new type of photoconductivity in semiconductor heterojunctions has been observed. The structures are InP/In0.47Ga0.53As forward-biased multiquantum-well p-n junctions grown by chemical-beam epitaxy. This phenomenon manifests itself in a photocurrent proportional to the dark differential conductance. This effect is associated with the partial screening of the electric field in the wells induced, at constant bias, by photogenerated carriers in the wells. The resulting increase of the field in the barriers leads to enhanced injection and photocurrent gain.

Notes: Distinct antiphase domain structures in GaAs epitaxial layers grown on a Si/SiO2/Si-substrate structure by metalorganic chemical vapor deposition have been revealed by using a silicon etchant (HF/HNO3). The antiphase is characterized by the [011]-oriented etching textures which rotate 90° between adjacent domains. The corresponding lattice rotation is further confirmed by a convergent beam electron diffraction technique. The size of the antiphase domains is found to increase with increasing film thickness and to grow upon annealing at temperatures above 700 °C. The maximum size of the domain, however, is found to be limited by the film thickness. The majority of the domain boundary lines revealed by chemical etching on the (100) surface do not correspond to any crystalline orientation. Only small segments are found to orient along [011], [010], [021], and, occasionally, [031] and [041] directions. Cross-sectional transmission electron microscopy studies confirmed that the boundaries are generally in curved configurations or zigzag configurations constituted of (011), (010), and (121) planes. All the boundaries are initiated at the interface and propagate through the film in the growth direction. Diffraction contrast experiments show a stacking-faultlike contrast of intrinsic type, indicating an inward relaxation of the lattice planes at the boundary. The rapid chemical reaction of the boundary with the silicon etchant, the intrinsic nature of the lattice distortion at the boundary, and the curved configuration of the boundary indicate that the boundary atoms are replaced by Si atoms. The higher concentration of Si atoms at the antiphase boundary has further been verified by energy dispersive x-ray analysis. In view of the reduction of bond distortion energy, the segregation of Si atoms at the antiphase boundary eliminates the highly distorted GaGa and AsAs bonds and is, therefore, an energetically favorable process. The possible antiphase boundary structure and a mechanism for its migration are discussed. Spatially resolved photoluminescence and cathodoluminescence studies reveal that both the antiphase boundaries and the defective interfacial regions contain nonradiative recombination centers. The luminescence efficiency of the domains increases strongly after annealing.

Notes: We present the materials growth and properties of both epitaxial and amorphous films of Gd2O3 (κ=14) and Y2O3 (κ=18) as the alternative gate dielectrics for Si. The rare earth oxide films were prepared by ultrahigh vacuum vapor deposition from an oxide source. The use of vicinal Si (100) substrates is key to the growth of (110) oriented, single domain films in the Mn2O3 structure. Compared to SiO2 gate oxide, the crystalline Gd2O3 and Y2O3 oxide films show a reduction of electrical leakage at 1 V by four orders of magnitude over an equivalent oxide thickness range of 10–20 Å. The leakage of amorphous Y2O3 films is about six orders of magnitude better than SiO2 due to a smooth morphology and abrupt interface with Si. The absence of SiO2 segregation at the dielectric/Si interface is established from infrared absorption spectroscopy and scanning transmission electron microscopy. The amorphous Gd2O3 and Y2O3 films withstand the high temperature anneals to 850 °C and remain electrically and chemically intact. © 2001 American Institute of Physics.

Notes: The incorporation of Sn into Ga0.47In0.53As grown at 450 °C by hydride source molecular beam epitaxy at concentrations ranging from about 3×1018 to 1×1021 Sn/cm3 has been investigated. Sn is a well behaved donor to about n=1020 cm−3, although increasing compensation is noted with increasing doping. At total concentrations beyond about 1020 cm−3 added Sn is not electrically active although the epitaxial quality remains high without noticeable morphology changes, defects, or precipitates, to at least 1021 Sn/cm3 .

Notes: Observation of energy-dependent transmission of nonequilibrium minority electrons through a symmetric double-barrier (DB) quantum well heterostructure is reported. The DB is placed in the base of a GaInAs/AlInAs bipolar transistor. The electrons are launched into the DB with variable kinetic energies using a tunnel barrier in the emitter and varying the emitter-base voltage. The resulting peak in the collector current provides for the first time evidence of quasi-ballistic resonant tunneling of minority carriers into the eigenstates of a quantum well. The small peak-to-valley ratio and the broad peak also demonstrate the importance of scattering and of the anisotropy in momentum space of the incident distribution function in the region between the ballistic electron launcher and the DB.

Notes: The light emission characteristics of high performance InGaAs/InP single quantum well laser diodes with a monolithically integrated intracavity loss modulator have been investigated. We demonstrate efficient voltage-controlled tuning of the lasing threshold current over more than one order of magnitude. In addition, active Q switching of 7 mW lasing light power with a change in electrical power of 〈30 μW is achieved.

Notes: We report the fabrication of enhancement mode InGaAsP/InP metal-semiconductor field-effect transistors having gate lengths of 2 μm. The epitaxial layers for this structure have been grown by chloride vapor phase epitaxy. The devices show extrinsic transconductances as high as 220 mS/mm, a short-circuit current gain cutoff frequency of fT=5.2 GHz, and a maximum available power gain cutoff frequency of fmax=9.5 GHz. A novel gate technology has been utilized where a lower band-gap quaternary InGaAsP layer of about 350 A(ring) thickness is grown on the top of the InP channel layer.

Notes: We report properties of device quality Hg1−xCdxTe grown by a precracking metalorganic chemical vapor deposition technique. The refinement of the low-temperature growth process and a higher purity metalorganic mercury source enable us to obtain material which has a carrier concentration of 2×1015 cm−3 and mobility as high as 330 000 cm2/V s. Infrared transmission spectra and the photoluminescence measurements obtained from this material will be presented. With further development in the synthetic route of the metalorganic mercury source, further improvement in the purity of the Hg1−xCdxTe is possible.

Notes: We report on a systematic study of atomic ordering in InGaAsP and InGaAs grown by atmospheric pressure metalorganic chemical vapor deposition. InGaAsP lattice matched to InP, grown in a temperature range of 625–650 °C, reveals atomic ordering on the (111) plane (variant I) and the (11¯1¯) plane (variant II) of the group III sublattice. The extent of atomic ordering increases with decreasing growth temperature and increasing In to Ga ratio. No orderings are observed in InGaAsP grown at 700 °C or in In0.53Ga0.47As lattice matched to InP at all our growth temperatures, in contrast to the commonly believed occurrence of maximum ordering at 1/1 In to Ga ratio. The facts that these conditions differ significantly from the reported conditions for InGaAsP grown by other techniques strongly suggests that the atomic ordering formation is controlled by the surface kinetics and growth environment, i.e., chemistry at the reactive gas-solid surface, fluid dynamics of the reactive gases, and growth temperature, rather than the composition and growth temperature. A fine structure observed in the superspots associated with the atomic ordering in the electron diffraction pattern indicates a possible superlattice structure formed by alternating variant I and variant II ordered layers. Misfit strain as well as sulfur dopant are shown to have no effect on the atomic ordering. Zinc dopant, however, totally eliminates the atomic ordering and shifts the energy band gap to a larger band gap.

Notes: Record low threshold current densities have been achieved in InGaAs/InGaAsP step graded index sep[AV:arate confinement (GRIN SCH) quantum well lasers emitting close to 1.50 μm. Single (SQW) and multiple (MQW) quantum well lasers with 300–500 μm long cavities had threshold current densities as low as 1.9 and 0.9 kA/cm2, respectively. In longer cavity devices, threshold current densities as low as 750 and 450 A/cm2 have been measured in SQW and MQW lasers, respectively. These lasers show no significant change in threshold current density with well thicknesses varying from 5 to 25 nm which demonstrate the effectiveness of the graded index in the carrier capture process. Buried-heterostructure GRIN SCH SQW and MQW with active layer widths of ∼2 μm show threshold currents of 15 and 9 mA, respectively.