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1

Digitale Medien

Strong negative transconductance in in-plane-gate transistors written by focused-ion-beam implantation (1994)

Bever, T. ; Hirayama, Y. ; Tarucha, S.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 75 (1994), S. 7573-7575

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A strong negative transconductance is investigated in in-plane-gate transistors written by focused-ion-beam implantation in the two-dimensional electron gas in modulation-doped AlGaAs/GaAs heterostructures. This occurs in a configuration where two in-plane gates G1 and G2 used to control the current through a channel lying between them are biased with different voltages Vg1 and Vg2. When the voltage Vg2〈0 is held constant, the current through the channel can be reduced to zero by increasing Vg1 beyond a critical value. In an earlier study this effect was attributed to velocity modulation. It is found, however, that in this regime Vg1 causes a very small current Ig2 to flow across gate G2. It is observed that changes in Id are correlated to changes in Ig2 and thus conclude that Ig2 is responsible for the strong negative transconductance.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.356610

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2

Digitale Medien

Enhanced collimation in narrow channels fabricated by focused-ion-beam implantation (1994)

Bever, T. ; Hirayama, Y. ; Tarucha, S.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 75 (1994), S. 2477-2480

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We investigate the collimation factor of narrow channels defined by focused-ion-beam insulation writing in the highly mobile two-dimensional electron gas of an AlGaAs/GaAs heterostructure. We show that the degree of collimation can be enhanced by appropriate channel design. Additional boundary roughness caused by selective implantation of ions along the channel boundary considerably increases the collimation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.356245

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3

Digitale Medien

Lateral spreading of focused ion-beam-induced damage (1992)

Bever, T. ; Jäger-Waldau, G. ; Eckberg, M. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 72 (1992), S. 1858-1863

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We study the lateral spreading of implantation-induced damage and measure the position dependence of the cathodoluminescence intensity of GaAs/AlAs heterostructures patterned by a focused Ga+ ion beam. Two luminescence lines, one from a buried AlGaAs/GaAs quantum well and the other from a deeper lying AlAs/GaAs short period superlattice are detected. Implantation doses in the range 1012–1015 cm−2 are investigated. We find that the lateral spreading of implantation induced damage considerably exceeds the implanted region in the case of the quantum well (50 nm below the surface), but is well limited to the implanted region in the case of the superlattice (250 nm below the surface). Micro-Raman measurements allow us to locally probe the degree of crystallinity at a certain point of the sample.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.351658

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4

Digitale Medien

Structural properties and transport characteristics of pseudomorphic GaxIn1−xAs/AlyIn1−yAs modulation-doped heterostructures grown by molecular-beam epitaxy (1992)

Tournié, E. ; Tapfer, L. ; Bever, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 71 (1992), S. 1790-1797

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Non-lattice-matched GaxIn1−xAs/AlyIn1−yAs modulation-doped heterostructures grown on (100) InP by molecular-beam epitaxy suitable for application in field-effect transistors have been studied. A computer simulation of the x-ray diffraction pattern proves to be necessary to obtain precise information about the structural parameters of the samples. The high crystal quality of our samples is demonstrated by the excellent agreement between experimental and simulated x-ray-diffraction curves. The transport characteristics of Ga0.38In0.62As/AlyIn1−yAs heterostructures including the evolution of the mobility and of the two-dimensional electron-gas density with temperature and structural parameters are discussed in relation with the relevant scattering mechanisms. The use of a thin spacer layer makes it possible to obtain very high conductivities. Both x-ray and transport measurements show that the strained GaxIn1−xAs layers are pseudomorphic well above the critical thickness calculated with the mechanical equilibrium model. The highest mobilities (13 100 and 103 000 cm2 V−1 s−1 at 300 and 4 K, respectively), obtained with a sheet carrier density of 1.7×1012 cm−2, are measured on a Ga0.38In0.62As/Al0.51In0.49As heterostructure. They are among the best values reported so far for similar structures.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.351215

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5

Digitale Medien

Deep level transient spectroscopy on focused ion beam written in-plane capacitances (1993)

Bever, T. ; Pfeiffer, G. ; Prescha, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 74 (1993), S. 6088-6093

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We discuss defects created by focused Ga ion beam implantation in GaAs or AlGaAs/GaAs heterostructures using deep level transient spectroscopy (DLTS). A novel contact configuration which is sensitive to defects located at the boundary between implanted and unperturbed regions at a well-defined depth is presented. The DLTS spectra for these samples are dominated by a peak with an activation energy of Ea=0.38 eV. The results show that this peak is associated with implantation-induced damage independent of the ion species. The defect is also found in a sample with Schottky contacts on top of a Ga-implanted GaAs layer.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.355193

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6

Digitale Medien

Velocity modulation in focused-ion-beam written in-plane-gate transistors (1993)

Bever, T. ; Klitzing, K. v. ; Wieck, A. D. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 63 (1993), S. 642-644

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The mobility of a one-dimensional electron gas can be changed markedly by moving the electron path from the high-mobility channel toward the low-mobility focused ion-beam-implanted regions. This can be done simply by applying different biases to the two adjacent in-plane gates. When the bias voltage on one gate is fixed, we increase the other gate potential and force the current path close to the ion-implanted region. In this way the mobility rather than the density of the carriers is controlled, which is the key feature of the velocity modulation transistors with inherently fast response.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.109976

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