Local barrier height (LBH) of Si(001) surface was studied using light-modulated scanning tunneling spectroscopy (LM-STS), which enables the observation of the tip-sample-dependent LBH with or without photoillumination simultaneously. The bias voltage and tip-sample distance dependence of LBH were comprehensively understood by the tip-induced band bending (TIBB), which influences the scanning tunneling microscopy and spectroscopy (STM/STS) in measurement of the local electronic structures of semiconductors. A marked decrease in surface photovoltage caused by photocarrier tunneling at shorter tip-sample distance was also shown. On the basis of these results, a method to measure LBH free of TIBB is discussed.

Undesirable electromagnetic waves radiated from various electrical and electronic apparatus recently have become social problems. Research to prevent these effects is in progress in various fields. This paper presents a method of determining the location of electromagnetic wave sources two‐dimensionally. The analysis method is based on the deduction of the power spectrum by applying the maximum entropy method to time‐series information, i.e., the location of electromagnetic‐wave sources in two‐dimension, corresponds to the power spectrum. It is confirmed by computer simulation that the location can be determined with very high accuracy. The relationship between the amount of data measured and the accuracy of location determination, and the relationship between the accuracy of a source‐location detection and the offset of the measuring position, were examined. The number of measurements was found to be almost twice the number of electromagnetic sources, and the detection of the location of a source can have a very high resolution if the measuring position is kept at a high accuracy. The results show that this method is very effective in determining the position of sources, for example, radiated from a system consisting of subsystems.

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Unwanted electromagnetic waves radiated from equipment making use of electromagnetic energy create numerous societal problems. The prevention of these problems has been studied extensively. In this paper, a method for estimating the location of the unwanted electromagnetic waves is studied. Since it is difficult to make the antenna aperture large especailly at low frequencies, a search for electromagnetic wave source via a synthetic aperture technique is proposed. In the estimated electromagnetic source distribution by this method, images similar to the antenna sidelobes appear. It is demonstrated by computer simulation that the images can be suppressed by use of the synthetic aperture method with subarrays or use of Mill's cross method. Discrepancies between the true source location and the estimated location have been found in regard to the synthetic aperture length and the geometrical relationship with respect to the aperture center. It has been found that the antenna configuration with the synthetic aperture length of 10 λ can estimate an electromagnetic wave source within 10 λ square with accuracy of less than 1/4 λ square. Therefore this method is sufficiently practical if the location of the source is restricted somewhat.

Effects of hydrogen on the morphology and electrical properties of GaN grown by plasma-assisted molecularbeam epitaxy Appl. Phys. Lett. 86, 121914 (2005); 10.1063/1.1890482 Effect of template morphology on the efficiency of InGaN ∕ GaN quantum wells and light-emitting diodes grown by molecular-beam epitaxy Appl. Phys. Lett. 86, 121110 (2005); 10.1063/1.1884745Effect of N to Ga flux ratio on the GaN surface morphologies grown at high temperature by plasma-assisted molecular-beam epitaxy GaN homoepitaxial layers of improved surface morphology were obtained by a NH 3 -source molecular-beam epitaxy method supplying a proper reactive NH 3 -to-Ga flux ratio ͑V/III ratio͒ on the growing surface, combined with a procedure to prevent the surface roughening of the GaN/ ͑0001͒ Al 2 O 3 epitaxial templates, which were prepared by metalorganic vapor-phase epitaxy. In situ monitoring on the heated templates revealed their thermal decomposition above 700°C in ultrahigh vacuum, which gave rise to surface unevenness of both initially atomically flat templates and the homoepitaxial layers. The surface flatness was maintained by depositing the ''flux-modulated'' GaN prior to the high-temperature growth, where Ga flux was supplied intermittently during heating the template under continuous NH 3 flow. The increase in V/III ratio greatly improved the surface flatness. As a result of the epilayer/template interface control and growth optimization, the epilayers exhibited higher mobility, smaller full width at half-maximum value ͑34 meV͒ of excitonic photoluminescence ͑PL͒ peak, and longer PL lifetime of 180 ps at 293 K.