Thin film growth of pentacene on SiO 2 using a supersonic source has been investigated with in situ real time synchrotron x-ray scattering and ex situ atomic force microscopy, focusing on the effects of incident kinetic energy E i and growth rate GR on the evolution of surface roughness and the crystalline structure of the thin films. For the conditions examined here, E i = 2.5-7.2 eV and GR= 0.0015-0.2 ML s −1 , the thin film phase is always observed. We find that while the effect of E i on interlayer transport is minimal, at high growth rates, slightly smoother films are observed.

Ballistic electron emission microscopy (BEEM) has been used to determine the Fermi-level pinning position at the Au/InAs interface. Using BEEM’s three-terminal capabilities, collector current–voltage scans were taken on Au/InAs/AlSb samples. The extracted BEEM threshold values (1.22 eV) correspond to the highest energy band position in the conduction band at the InAs/AlSb interface. By subtracting the InAs/AlSb conduction-band offset (1.35 eV), an estimate of the Au Fermi-level position on InAs is obtained (0.13 eV).

Ballistic electron emission microscopy (BEEM) has been used to study transport in a double barrier resonant tunneling structure. Unlike conventional transport techniques, BEEM allows the injected electron energy to be varied independent of the band profile. We report the observation of quasi-bound states and band-structure effects as deduced from the temperature evolution of the BEEM spectra. The BEEM thresholds are found to be in good agreement with the calculated energetically favorable levels. Our results show that BEEM is a powerful spectroscopic tool for studying quantum structures.

We report an extensive investigation of semiconductor band-structure effects in single-barrier Al x Ga 1Ϫx As/GaAs heterostructures using ballistic-electron-emission spectroscopy ͑BEES͒. The transport mechanisms in these single-barrier structures were studied systematically as a function of temperature and Al composition over the full compositional range (0рxр1). The initial ͑⌫͒ BEES thresholds for Al x Ga 1Ϫx As single barriers with 0рxр0.42 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 ͑xϾ0.45͒, spectra show a weak ballistic-electron-emission microscopy current contribution due to intervalley scattering through Al x Ga 1Ϫx As X valley states. Low-temperature spectra show a marked reduction in this intervalley current component, indicating that intervalley phonon scattering at the GaAs/Al x Ga 1Ϫx As interface produces a significant fraction of this X valley current. A comparison of the BEES thresholds with the expected composition dependence of the Al x Ga 1Ϫx As ⌫, L, and X points yields good agreement over the entire composition range. ͓S0163-1829͑97͒04827-3͔

Ballistic electron emission microscopy (BEEM) has been used to study electron transport across single barrier AlxGa1−xAs/GaAs heterostructures. The structures, grown by molecular beam epitaxy, utilized a p-type δ-doped sheet to cancel the band bending near the Schottky interface, enabling a direct measurement of the conduction band offset at room temperature. The band offset at room temperature for x=0.21 is 0.19 eV and for x=0.42 is 0.33 eV. Measurements at 77 K gave values of 0.20 eV for x=0.21 and 0.35 eV for x=0.42. These results demonstrate that BEEM can be used to probe the transport properties of semiconductor heterostructures which are spatially beneath the Schottky barrier.