Eiichi Yamaguchi

Effect of pyrolytic Al2O3 deposition temperature on inversion‐mode InP metal‐insulator‐semiconductor field–effect transistor

The effects of pyrolytic Al2O3 deposition temperature on electrical properties of an inversion‐mode InP (MISFET) metal‐insulator‐semiconductor field‐effect transistor were investigated. An Al2O3 gate insulator was deposited using an aluminum isopropoxide organic source on a HCl vapor etched InP surface. An increasing current drift was seen when the insulator was deposited at a temperature below 330 °C. This became exaggerated with decreasing temperature. The observed drift is explained in terms of a time‐dependent threshold voltage associated with the polarization of organic molecules or radicals introduced into the insulator by an incomplete decomposition of the source gas during deposition of the dielectric layers at rather low temperatures. The effective electron mobility of the InP MISFET did not show any dependence on the deposition temperature below 350 °C. At higher temperatures, the effective mobility appreciably decreased.

Study of boron nitride gate insulators onto InP grown by low‐temperature chemical vapor deposition

Thin films of phosphorus‐doped boron nitride have been grown onto InP, as a new gate insulator, by low‐temperature chemical vapor deposition using the reaction of NH3, B2H6, and PH3. Characteristics of the pyrolytic boron nitride obtained have been investigated by ellipsometry, x‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and conductivity measurement. The results of XPS and AES have shown that a stable and comparatively stoichiometric boron nitride film was successfully obtained, even at low temperatures (300–600 °C), by using the two‐temperature zone technique. The density of interface states for the BN/InP system has been found to be about 1010 cm−2 eV−1 or less around the midgap.

The Origin of the DX Center in AlxGa1-xAs

A new microscopic origin of the DX center in AlxGa1-xAs is proposed on the basis of the scattering-theoretic method calculation. Calculated results show that the central cell potential of donors induces the deep levels attributed to the DX center. The theory satisfactorily explains the x- and pressure-dependence of the DX center energy levels in AlxGa1-xAs.

Theory of the DX Centers in III-V Semiconductors and (001) Superlattices

Deep donor levels which are referred to as the DX centers are calculated using the scattering-theoretic method in Al x Ga 1- x As, GaAs 1- y P y and Al x Ga 1- x Sb semiconductors, and also GaAs-AlAs and GaSb-AlSb (001) superlattices. The calculated results show that the deep levels attributable to the DX centers are incluced by the central cell potential of substitutional donors. The theory quantitatively explains experimental results on the DX centers in III-V semiconductors and superlattices.

Cold Nuclear Fusion Induced by Controlled Out-Diffusion of Deuterons in Palladium

A gigantic neutron burst of (1-2)×106 n/s has been detected from deuterated Pd plates with heterostructures set in a vacuum chamber. An explosive release of D2 gas, biaxial bending of all the samples, and excess heat evolution were also observed at the same time. It has been concluded that these phenomena are caused by the cooperative production of D accumulation layers at Pd surfaces due to controlled out-diffusion of D-atoms.

Effects of nitrogen vacancy on optical properties of nitride semiconductors

Band structures and deep levels are calculated for both the cubic and hexagonal nitride semiconductors, using the sp 3 s * tight-binding formulation and the Greens function technique. An anti-bonding s-like state produced by nitrogen vacancy is predicted to appear at 0.3 eV below the conduction-band (CB) edge for GaN, which gets shallower and then resonant with the CB for In x Ga 1- x N with In content (x). The theoretical results can provide a new and consistent model for explaining anomalous optical properties in nitride semiconductors.

Electron correlation effects on Anderson localized states

Abstract A theoretical model is presented to investigate the effects of electron correlation on the Anderson localized states, and the spin susceptibility and electronic specific heat are calculated. It is shown tha a remarkable effect of correlation in the intermediate region is to give rise to the Curie type behaviour at low temperatures in the spin susceptibility which otherwise obeys the Pauli law. It is further shown that the correlation effect on the T linear term in the specific heat is very small.

Theory of defect scattering in two‐dimensional multisubband electronic systems on III‐V compound semiconductors

A theory of defect scattering has been developed for two‐dimensional electron gas in metal‐insulator‐semiconductor field‐effect transistors (MISFETs) on III‐V compound semiconductors. An analytic formula has been obtained for the transport relaxation time limited by the defect scattering with intra‐ and intersubband transitions. The theory has been able to phenomenologically explain the experimental results for temperature dependence and Ninv (inversion electron concentration) dependence of the mobility on InAs and InP MISFETs. The abrupt decrease observed in the mobility at 1.2×1012 cm−2 of Ninv on InAs has been found to be due to the intersubband defect‐scattering effect on ground subband electrons.

Chemical deposition of PAsxNy films onto III–V compound semiconductors

A new insulating film of composition PAsxNy was fabricated on III–V compound semiconductors by a chemical vapour deposition method. It was found that the introduction of arsenic strongly decreases the density of interface states near the conduction band edge (approximately 1011 cm-2 eV-1) in InP. The effective mobility for inversion-mode InP/PAsxNy metal/insulator/semiconductor field effect transistors was 1200−1400 cm2 V-1 s-1.

Isothermal Capacitance Transient Spectroscopy in MIS Structures

A general formula for the capacitance transient response in an MIS structure has been developed, including the continuous density distribution of interface states and discrete multi-impurity levels. A new method of spectroscopic measurement is proposed for determining the density distributions and capture cross-sections of interface states and bulk impurity levels under isothermal conditions. The method is then applied to an n-InAs/anodic oxide MIS diode.