Hideo Ohno

Hokkaido University, Sapporo-shi, Hokkaido, Japan

Are you Hideo Ohno?

Claim your profile

Publications (51)77.98 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The electrical properties of midgap states in n‐type Al x Ga 1-x As grown by the metalorganic vapor phase epitaxy were investigated by the deep level transient spectroscopy and photocapacitance (PHCAP) techniques. A new PHCAP measurement procedure to avoid interference from the photoionization of the DX center was used. Two near‐midgap levels, i.e., a higher lying MH level and a lower lying ML level were detected. As AlAs mole fraction, x, is increased, the energy positions of these two levels became deeper, maintaining a remarkable horizontal alignment with respect to the hybrid orbital energy level. The ML level showed a clear photoquenching for x≪0.3, but the quenching disappeared for x≳0.3. No photoquenching of the MH level was observed for all x investigated. Similarity of the photoquenching behavior to GaAs  1-x  P x as well as its energy position and optical cross sections led to the conclusion that the ML level is an As‐related EL2‐like defect. On the other hand, the MH level originates from a defect related to Al.
    Journal of Applied Physics 11/1990; · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The feasibility of molecular-beam epitaxy (MBE) and migration-enhanced epitaxy (MEE) growth of InP in the standard GaAs-type MBE chamber was demonstrated using polycrystalline InP as the phosphorus source. The substrate was a semi-insulating (Fe-doped) InP substrate with (100) orientation. Prior to growth, the substrate was thermally cleaned either under P<sub>2</sub> flux or under As<sub>4</sub> flux. The change of the surface structure was detected by the change in the reflection high-energy electron diffraction (RHEED) pattern taken at an acceleration voltage of 14.5 kV. The RHEED intensity oscillation was measured on the specular beam spot, using a videocamera system. InP polycrystal was shown to be suitable for the MEE growth mode, giving a strong enhancement of photoluminescence intensity
    Indium Phosphide and Related Materials, 1990. Second International Conference.; 05/1990
  • Surface Science 01/1990; 228:497. · 1.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The quantum Hall effect of electrons in AlGaAs/Ga1−x Inx As/GaAs pseudomorphic strained heterostructures is reported for the first time. Despite the large strain induced by the lattice mismatch, clear quantum Hall plateaus and Shubnikov–de Haas oscillation are observed, indicating the presence of a well behaved two‐dimensional electron gas. Although the mobility of the sample is fairly low, a pronounced asymmetry in the spin splitting of the magnetoresistivity appears at high magnetic fields in contrast to the previous results on AlGaAs/GaAs structures where asymmetry appears only in the high‐mobility samples and disappears when the mobility is lower. This indicates that the shape of the state density is not influenced significantly by the presence of the high concentration of the short‐range cluster‐scattering centers.
    Journal of Applied Physics 11/1989; 66(9). · 2.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The transverse magnetoconductivity σxx of a two-dimensional electron gas (2D EG) in selectively doped Al0.3Ga0.7As/ Ga1-xInxAs/GaAs pseudomorphic structures is shown to behave very differently from that of the Al0.3Ga0.7As/GaAs structures in the quantum Hall regime. Well-defined peaks of transverse conductivity σxx corresponding to each Landau level were observed and their peak heights increased with the increase of InAs composition. Also, the peak height of σxx increases with the Landau number N in the pseudomorphic structure, especially for samples with x≥0.13 σxx varies in proportional to N+(1/2, whereas it remains almost unchanged when N increased in the AlyGa1-yAs/GaAs structures. The behavior of σxx for the pseudomorphic structure is very similar to that of the 2D EG formed in the inversion layer of the Si metal-oxide-semiconductor field-effect transistor. The observed difference between the pseudomorphic structure and the AlyGa1-yAs/GaAs heterostructure is interpreted in terms of the change in the dominant scattering mechanism, i.e., the short-range cluster scattering in the former, and the long-range scattering in the latter.
    Physical review. B, Condensed matter 09/1989; 40(5). · 3.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hydrogenated amorphous carbon (a‐C:H) films were prepared at room temperature by low‐frequency (50‐Hz) plasma chemical vapor deposition using CH 4 and H 2 . The a‐C:H films were transparent, highly resistive, and very uniform. Infrared absorption measurements, as well as Raman spectroscopy, indicated that the C bonding in the a‐C:H films was predominantly sp<sup>3</sup> . Moreover, the optical band gap of the a‐C:H films was measured.
    Journal of Applied Physics 08/1989; · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Low‐field mobility of two‐dimensional electron gas (2DEG) in selectively doped pseudomorphic N‐Al 0.3 Ga 0.7 As/ Ga 0.8 In 0.13 As/GaAs structures was measured as a function of carrier concentration as well as a function of temperature. In order to explain the observed mobility characteristics, scattering due to clustering has been considered. It is shown that the low‐field mobility of 2DEG at low temperature (≪40 K) can be explained by the scattering due to clustering together with the remote ionized impurity scattering.
    Applied Physics Letters 02/1989; · 3.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The complex recombination process through quantum states at compound semiconductor surfaces and hetero-interfaces is analyzed in a unified manner on the computer, using the unified disorder induced gap state (DIGS) model. Recombination through uniformly distributed states at surfaces and hetero-interfaces, and that through U-shaped surface states at GaAs surfaces subjected to various surface treatments, are specifically analyzed. The result indicates that the effective surface recombination velocity is not constant, but is strongly dependent on the excitation intensity and the location of charge neutrality level, EHO. PL intensity enhancement after photochemical oxidation in water and sulfur treatments (Na2S, (NH4)2S) is shown to be not due to reduction of the durface states, but due to the generation of a fixed charge, whereas photochemical HCl treatment reduces the surface states significantly.
    Applied Surface Science 01/1989; 41:402-406. · 2.54 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Provides information on hydrogenated amorphous carbon films prepared at room temperature by low frequency plasma chemical vapor deposition using methane and hydrogen. Measurement of resistivity and breakdown electric field after deposition; Infrared absorption spectrum of the grown film for the carbon-hydrogen stretching mode region; Raman spectroscopy using argon laser excitation. http://search.epnet.com/login.aspx?direct=true&db=afh&an=7648244
    Journal of Applied Physics 01/1989; · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Clean surfaces of GaAs and InAs prepared by molecular beam epitaxy have been epitaxy have been exposed to trimethylgallium and diethylgalliumchloride at various temperatures and the resultant change has been observed in situ by X-ray photoelectron spectroscopy. Saturation of amount of Ga deposited onto the surface to about 1 monolayer has been observed at substrate temperature above 320°C, which results in atomic layer epitaxy. No appreciable increase of carbon nor chlorine has been observed after exposure to group III alkyls.
    Journal of Crystal Growth 01/1989; 95:132-135. · 1.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electrical characterization reveals several salient common electronic features of insulator-semiconductor (I-S) and semiconductor-semiconductor (S-S) interfaces. Currently available models on the origin of states (defect model, DIGS model, effective workfunction model) are compared in their capabilities of explaining these features. The DIGS (disorder-induced gap state) model is shown to possess maximum capability and consistency. Study of the microstructure of interface by cross-sectional TEM and RBS techniques revealed a strong correlation between lattice disorder and interface state density, and supports the DIGS model.
    Applied Surface Science 01/1989; 41:372-382. · 2.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Clean surfaces of molecular beam epitaxially grown GaAs were exposed to diethylgalliumchloride (DEGaCl) and the resultant change was observed by insitu x-ray photoelectron spectroscopy. At a substrate temperature of 300 °C, a self-limiting reaction between DEGaCl and the surface resulted in one monolayer of Ga deposition which is believed to lead to atomic layer epitaxy of GaAs using DEGaCl. No appreciable increase of Cl or C was observed after exposure. Discussion on the mechanism of the self-limiting reaction is also presented.
    Applied Physics Letters 01/1989; 54:1124-1126. · 3.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An X-ray photo-electron spectroscopy (XPS) analysis is applied to clarify the composition of the InP insulator-semiconductor structures prepared by the anodic oxidation process. The structures investigated include (i) an anodic oxide/InP structure, (ii) an Al2O3/native oxide/InP structure and (iii) a photo-CVD SiN/native oxide/InP structure. It is shown that condensed indium phosphate plays an important role in structures (i) and (ii). The composition control of the phosphate layer by anodization is demonstrated, and is explained by a simple mechinism of field driven movement of indium species. A correlation between phosphate composition and interface state density is found in structure (iii).
    Applied Surface Science 01/1989; 41:390-394. · 2.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An experiment was carried out to clarify the low field transport properties of two-dimensional electron gas in selectively doped (SD) AlGaAs/GaInAs/GaAs pseudomorphic structures. In order to clarify these properties, the electron effective mass and the electron scattering mechanisms were investigated using molecular-beam-epitaxy-grown SD-Al(0.3)Ga(0.7)As/Ga(0.87)In(0.13)As/GaAs structures.
    Japanese Journal of Applied Physics 10/1988; · 1.07 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Based on the recently proposed disorder-induced gap state (DIGS) model for interface states, the charge-discharge dynamics of interface state continuum at insulator-semiconductor (I-S) interfaces are theoretically analyzed and compared with the experiments on InP and InGaAs MIS structures. The concept occupation boundary used in the analysis clarifies the physics involved and simplifies the simulation of complex processes. By assuming a particular type of DIGS distribution in energy and in space, the observed complex hysteresis behavior of dispersion of MIS capacitance in MIS C-V curves as well as the current drift behavior of MISFET's are completely reproduced on computer, offering a unified understanding of a wide variety of phenomena associated with I-S interfaces.
    Applied Surface Science 09/1988; · 2.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effects of photochemical oxidation in water, Na 2 S deposition and exposure to NH 3 and HCl gas ambients on the Fermi level pinning, and the surface recombination process at GaAs surfaces were studied by measuring the band edge photoluminescence (PL) intensity, x‐ray photoelectron spectroscopy spectra, and surface current transport(SCT). Computer simulation of the surface recombination process was also made on the basis of the disorder‐induced gap state model. Marked increase of PL intensity was observed after both photochemical oxidation and deposition of Na 2 S as previously reported. However, SCT measurements on n‐type materials detected increase of surface band bending in the dark. Exposure to NH 3 resulted in a slight reduction in the band bending with little change in the PL intensity. Exposure to HCl, on the other hand, resulted in marked reduction of the band bending with marked increase of the PL intensity. The computer simulation shows that the contradictory behavior of the PL intensity and band bending, as observed after photochemical oxidation and Na 2 S deposition, is explicable by a shift of the Fermi level pinning position towards the valence band edge due to a fixed negative interface charge which reduces the effective recombination velocity. On the other hand, exposure to HCl reduces the surface‐state density and weakens the pinning remarkably.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 08/1988; · 1.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Compound semiconductor metal‐insulator‐semiconductor (MIS) capacitance‐voltage (C‐V) curves are simulated on a computer, assuming the presence of a disorder‐induced gap‐state (DIGS) continuum near the interface in which bonding and antibonding states are distributed both in space and in energy around a particular charge neutrality point, E HO . A program based on Shockley–Read–Hall statistics is developed and applied to simulate a set of experimental MIS C‐V curves measured on Al 2 O 3 /native oxide/InP MIS capacitors. By assuming a particular type of energy and spatial distribution of DIGS continuum and a suitable single set of dynamic parameters, the simulation can completely and self‐consistently reproduce the experimental MIS C‐V curves with complex hysteresis behavior, which varies with the bias amplitude and swing speed. The excellent agreement between theory and experiment supports the DIGS model. The danger involved in simply applying Terman’s method to determine an N ss distribution is pointed out. A quick procedure for reasonably accurate N ss measurement is suggested.
    Journal of Applied Physics 04/1988; · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Anodic oxidation in an ethylene glycol solution of potassium nitrate is shown to be capable of forming uniform amorphous layers on hydrogenated amorphous silicon (a‐Si:H) films at room temperature at a rate of 5.5 Å/V up to the maximum thickness of about 2500Å. The process is stable, reproducible, and electrically controllable. The oxidation process and the properties of the anodic oxide films are described, and a detailed comparison is made with the anodization of single‐crystal silicon. The anodization accompanies electroluminescence. The effect of illumination of the anode and the behavior of luminescence from the anode are discussed in detail in an attempt to clarify the electrical behavior of the anode during anodization. The anodic oxide of a‐Si:H displays resistivity of , breakdown strength of and a refractive index of 1.46 (at 6328Å).
    Journal of The Electrochemical Society. 01/1988; 135(2):424-431.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Modified molecular-beam epitaxy, in which group V flux is suspended during 1 monolayer (ML) deposition of group III elements, is employed for growth of strained GaAs/InAs superlattices on InP substrates with a GaInAs buffer layer. By the reflection electron diffraction intensity study and by X-ray photoelectron spectroscopy, the modification of growth procedure is shown to result in fast formation of a flat growth front without intermixing, which is necessary for superlattice growth. GaAs/InAs superlattice structures grown by the present method are characterized by X-ray diffraction and transmission electron microscopy.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/1988; 6(2):593-596. · 1.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Relationship between band edge photoluminescence (PL) and surface states is rigorously analyzed on computer, using the disorder-induced gap state (DIGS) model, and is compared with experiments on GaAs surfaces subjected to various treatments. It is shown that PL intensity is directly correlated with the effective surface recombination velocity, but is not necessarily directly correlated with the surface-state density (Nss) itself. PL enhancement by photochemical oxidation and by Na2S deposition is proposed to be due to a fixed negative charge, whereas photochemical treatment in HCl leads to significant reduction in Nss.
    Japanese Journal of Applied Physics 01/1988; 27. · 1.07 Impact Factor