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  • 1
    Electronic Resource
    Electronic Resource
    High-precision harmonic magnetic-field measurement and analysis using a fixed angle Hall probe (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2548-2555 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A special theoretical concept involving the harmonic magnetic-field measurement and analysis method using a fixed angle Hall probe was developed at the Synchrotron Radiation Research Center (SRRC) for measuring as well as analyzing the triple bending achromat magnets of the storage ring. The method can be used to simulate the harmonic magnetic-field calculation of the two-dimensional (2D) "magnet'' program. This method has a quite simple mechanism. The Hall plate was fixed at a 0° angle with respect to the horizontal plane of magnet to measure only the vertical field. Additionally, the 2D nonlinear least-square fitting was used to fit the mapping data so as to find the normal and skew multipole field strength. If necessary, the angle of Hall probe could be rotated 90° precisely for measuring the horizontal field. Consequently, the skew dipole field could be obtained. A real-time Hall-probe automatic magnetic-field measurement system was also developed for fulfilling the concept of the harmonic field measurement. Some special mapping trajectories for different kinds of magnets were discussed to match this special theoretical concept with the analysis methodology. This was done so as to obtain the reliable and accurate harmonic field strength. The accuracy and precision of the harmonic field strength measurement and analysis of this method being better than ±0.01% was confirmed by experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144650
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  • 2
    Electronic Resource
    Electronic Resource
    Photoreflectance temperature dependence of graded InAlAs/InGaAs heterojunction bipolar transistor layers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4035-4038 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance(PR) spectra of the graded InAlAs/InGaAs heterojunction bipolar transistor layers were investigated at various temperatures between 8 K and 300 K. The energy features of the PR spectra were fitted and identified as band-to-band transitions in the graded layers which were grown by pulsed molecular beam epitaxy (pulsed-MBE) and InGaAs as well as InAlAs layers. The temperature variation of energy gaps can be described by the Varshni and Bose-Einstein equations. A linear variation relationship of band gaps with Al composition (z) was observed and approximated to be E0(z)=0.809+0.769z eV at T=0 K. However, the parameters aB and aitch-thetaB derived from the Bose-Einstein expression do not change meaningfully in the whole range of Al composition. From the observed Franz-Keldysh oscillations (FKOs) we have evaluated the built-in dc electric fields in the i-InGaAs collector, i-InGaAs spacer and n-InAlAs emitter regions. The electric fields are in good agreement with the continuity condition of electric displacements in the interfaces between emitter and base. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359927
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  • 3
    Electronic Resource
    Electronic Resource
    Photoreflectance study on the two-dimensional electron gas of InAlAs/InGaAs heterojunction bipolar transistor grown by molecular beam epitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6681-6685 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InAlAs/InGaAs heterojunction bipolar transistor with a 300 A(ring) spacer inserted between emitter and base grown by molecular beam epitaxy was characterized by using photoreflectance spectroscopy. The energy features observed above the InGaAs fundamental band gap are attributed to the quantum confined subband transition of two-dimensional electron gas which was confined in the spacer channel. A detailed lineshape fit makes it possible to evaluate the Fermi energy, and hence the two-dimensional electron gas concentration. The behavior of two-dimensional electron gas at temperatures between 10 and 300 K was also characterized and the sheet-density in proportion to temperature was observed. Furthermore, using the temperature dependence of effective mass measured by cyclotron resonance combined with photoreflectance to analyze built-in electric field is also reported. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359081
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of piezoelectric (111)B InGaAs/GaAs p-i-n quantum well structures using photoreflectance spectroscopy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1208-1210 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strained-layer (111)B In0.2Ga0.8As/GaAs p-i-n quantum well structures grown with exciton transitions well resolved at room temperature have been studied by photoreflectance spectroscopy. Using the reduced mass deduced from experiments, the built-in electric field in the barrier region is obtained from the above band-gap Franz–Keldysh oscillations. The strain-induced piezoelectric field is then determined directly from a comparison of the periods of Franz–Keldysh oscillations in different samples. Numerical solutions for the exciton transitions from the derived potential profiles are in good agreement with the experimental results. The piezoelectric constant is also determined using the piezoelectric field. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121015
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  • 5
    Electronic Resource
    Electronic Resource
    Photoreflectance spectroscopy of strained-layer (111)B InGaAs/GaAs quantum well diodes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1595-1601 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InGaAs/GaAs (111)B quantum well p-i-n structures grown by gas source molecular beam epitaxy have been investigated with a photoreflectance technique. Using the reduced mass deduced from experiments, the built-in electric field is obtained from the above band-gap Franz–Keldysh oscillations (FKOs). The strain-induced piezoelectric field is then determined directly from the comparison of the periods of FKOs in different samples. Numerical solutions for exciton transition energies with the experimentally derived potentials are in good agreement with experimental results. Hence, the piezoelectric constant can be determined using the piezoelectric field. The temperature dependences of the quantized energy levels indicate that the influence of temperature on exciton transitions is essentially the same as that of the gaps of the relevant bulk constituent materials. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368229
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  • 6
    Electronic Resource
    Electronic Resource
    Implementation and use of general-purpose interface bus interface in an automatic testing and measurement system of a magnet power supply (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2488-2493 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A general-purpose interface bus (GPIB) interface card has been designed and installed on an IBM PC/XT microcomputer in order to make possible automated testing of a programmable dipole magnet power supply. This paper indicates how one can design and implement a GPIB interface and use it economically but effectively in testing and measuring the performance characteristics of the power supply. The overall system and associated software developed for the control and monitoring of the power supply are also described. The advantages of the system are stable operation, simplicity of hardware, the friendliness of software.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139935
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  • 7
    Electronic Resource
    Electronic Resource
    Photoreflectance characterization of graded InAlAs/InGaAs heterojunction bipolar transistor layers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2697-2699 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoreflectance (PR) spectroscopic technique has been used to investigate the microstructures of the graded InAlAs/InGaAs heterojunction bipolar transistor at room temperature. The energy features of the PR spectrum were fitted and identified as band-to-band transitions in the graded layers which were grown using pulsed molecular beam epitaxy and InGaAs as well as InAlAs layers. A linear variation relationship of band gaps with Al composition z was observed and approximated by Eg=0.737+0.759z eV. From the observed Franz-Keldysh oscillations, we have evaluated the built-in dc electric fields in the i-InGaAs collector and n-InAlAs emitter regions. These electric fields are in good agreement with the continuity condition of electric displacements in the interfaces. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113492
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  • 8
    Electronic Resource
    Electronic Resource
    Study of InAlAs/InGaAs heterojunction bipolar transistor layers by optically detected cyclotron resonance (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2543-2545 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an investigation of optical and electronic properties in InAlAs/InGaAs heterojunction bipolar transistor layers by optical detection of cyclotron resonance (ODCR). Strong ODCR spectra structured by quantum oscillations have been observed, from which the effective mass and the carrier concentration of the two-dimensional electron gas can be obtained. The measured cyclotron mass is heavier than the conduction-band-edge mass in bulk InGaAs. We find that the carrier concentration increases with the spacer thickness. Quite unexpectedly, we also find that the effective mass increases with decreasing the carrier concentration. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113161
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  • 9
    Electronic Resource
    Electronic Resource
    Erratum: "Study of InAlAs/InGaAs heterojunction bipolar transistor layers by optically detected cyclotron resonance'' [Appl. Phys. Lett. 66, 2543 (1995)] (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 727-727 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115560
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  • 10
    Electronic Resource
    Electronic Resource
    Photoreflectance characterization of an InAlAs/InGaAs heterostructure bipolar transistor (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1974-1976 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the photoreflectance spectrum at 300 K from a lattice-matched InAlAs/InGaAs heterostructure bipolar transistor grown by molecular beam epitaxy. The energy features of photoreflectance spectra have been identified and the built-in dc electric fields and associated doping profiles have been evaluated in the n-InAlAs emitter from the observed Franz–Keldysh oscillations. The undoped InGaAs spacer between emitter and base was added on to change the built-in electric field. The results showed that the energy features above the InGaAs band gap are the transitions from the valence band to the quantized state of the conduction band. The quantum well of the conduction band is in the interface of the InAlAs and InGaAs heterojunction. The interface charge densities in the spacer channel are determined to be 3.54×1011 cm−2 and 4.22×1011 cm−2, corresponding to the samples with spacer thicknesses of 300 and 500 A(ring), respectively. A triangular potential profile model was used to calculate the microstructure in the potential well and electron energy transition. The theoretical and experimental results were compared and good agreements were also found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111732
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