Ballistic-electron-emission spectroscopy of Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures: Conduction-band offsets, transport mechanisms, and band-structure effects

Journal Article · Tue Jul 01 04:00:00 EDT 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.2026· OSTI ID:527015

OShea, J J; Brazel, E G; Rubin, M E; Bhargava, S; Chin, M A; Narayanamurti, V ^[1]

---

1. Materials Department, Physics Department, and Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

We report an extensive investigation of semiconductor band-structure effects in single-barrier Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures using ballistic-electron-emission spectroscopy (BEES). The transport mechanisms in these single-barrier structures were studied systematically as a function of temperature and Al composition over the full compositional range (0{le}x{le}1). The initial ({Gamma}) BEES thresholds for Al{sub x}Ga{sub 1{minus}x}As single barriers with 0{le}x{le}0.42 were extracted using a model which includes the complete transmission probability of the metal-semiconductor interface and the semiconductor heterostructure. Band offsets measured by BEES are in good agreement with previous measurements by other techniques which demonstrates the accuracy of this technique. BEES measurements at 77 K give the same band-offset values as at room temperature. When a reverse bias is applied to the heterostructures, the BEES thresholds shift to lower voltages in good agreement with the expected bias-induced band-bending. In the indirect band-gap regime ({ital x}{gt}0.45), spectra show a weak ballistic-electron-emission microscopy current contribution due to intervalley scattering through Al{sub x}Ga{sub 1{minus}x}As {ital X} valley states. Low-temperature spectra show a marked reduction in this intervalley current component, indicating that intervalley phonon scattering at the GaAs/Al{sub x}Ga{sub 1{minus}x}As interface produces a significant fraction of this{ital X} valley current. A comparison of the BEES thresholds with the expected composition dependence of the Al{sub x}Ga{sub 1{minus}x}As {Gamma}, {ital L}, and {ital X} points yields good agreement over the entire composition range. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 527015
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 4 Vol. 56; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ALUMINIUM ARSENIDES
ALUMINIUM COMPOUNDS
CHEMICAL COMPOSITION
ELECTRON EMISSION
ELECTRONIC STRUCTURE
EMISSION SPECTROSCOPY
GALLIUM ARSENIDES
TEMPERATURE DEPENDENCE