Haruo Nagai

A new inorganic electron resist of high contrast

A novel inorganic electron resist is proposed. It is shown that the electron irradiation on a stacked layer composed of a thin Ag film over a layer of Se‐Ge chalcogenide amorphous glass enhances diffusion of Ag into Se‐Ge glass, in the same manner as in the case of photodoping. The Ag‐doped Se‐Ge film becomes almost insoluble in alkaline solutions. A negative‐type electron resist is realized by applying this effect. This inorganic electron resist is proved to exhibit an extremely high contrast (γ∼8). The sensitivity is 4×10−5 C/cm2 at 5 kV. It is confirmed that fine‐pattern delineation of less than 0.3 μm linewidth is possible.

A novel inorganic photoresist utilizing Ag photodoping in Se‐Ge glass films

By ’’photodoping’’ with silver, chalcogenide glasses become almost insoluble in alkaline solutions. This letter examines the applicability of this effect to silicon microfabrication technology. Suitable processing techniques and exposure characteristics are investigated. It is shown that the (Ag) ‐Se‐Ge glass system can be used as a negative‐type photoresist; fine pattern photoetching of less than 1 μm line width in SiO2 is easily achieved. This inorganic photoresist has some advantages over the conventional polymer‐type photoresists in resolution, etch resistance to acid solutions, and process reproducibility.

Molecular beam epitaxial growth of InGaAlP visible laser diodes operating at 0.66–0.68 μm at room temperatures

The room temperature pulsed operation of In0.49Ga0.31Al0.20P/In0.49Ga0.51−x AlxP/In0.49Ga0.31Al0.20P(x=0.00–0.03) double heterostructure (DH) laser diodes have been achieved for the first time. The lasing wavelength was 0.66–0.68 μm with a threshold current density of 2.6–3.6×104A/cm2 at 26 °C. These results were achieved by growing DH wafers by molecular beam epitaxy (MBE). Key points in the successful MBE growth of these DH wafers were, first, the realization of low resistance p‐type and n‐type InGaAlP layers by reducing contamination in the growth chamber. This was done by installing a substrate loading room with an interlock valve and a substrate transfer mechanism. The second was the realization of an abrupt p‐n junction by the use of Si instead of Sn as an n‐type dopant.

InP‐GaxIn1−xAsyP1−y double heterostructure for 1.5 μm wavelength

InP/GaxIn1−xAsyP1−y/GaxIn1 −x AsyP1−y double‐heterostructure LED’s in a 1.5‐μm‐wavelength region have been fabricated by the LPE method. The half‐width value of the spectrum is about 1100 A, and the external quantum efficiency is 1.5% for undoped active layers of Ga0.28In0.72As0.77P0.23. The threshold current density of the laser oscillation at 1.52 μm and 300 K is 104 A/cm2 μm. No symptom of an initial degradation has been observed.

Molecular beam epitaxial growth of InGaAlP on (100) GaAs

InGaAlP epitaxial layers that are lattice matched to (100) GaAs substrates have been successfully grown for the first time by molecular beam epitaxy. The surface of the grown crystal is mirror smooth, and the full width at half‐maximum of the double crystal x‐ray diffraction pattern is less than 100 sec. The energy gap at the Γ point increases from 1.9 eV (InGaP) to 2.5 eV (InAlP) with increasing AlP mole fraction. The optical waveguide effect was also observed in InGaP/InGaAlP double heterostructure wafers.

Crack formation in InP‐GaxIn1−xAs‐InP double‐heterostructure fabrication

InP‐Ga0.47In0.53As‐InP double‐heterostructure laser diodes which emit infared radiation near 1.6 μm were prepared. At 77 K, the laser threshold current density was about 2500 A/cm2. Cracking of GaxIn1−xAs epitaxial layers on InP substrates due to lattice mismatch was observed, and the composition range of GaxIn1−xAs in which no cracking occurred was found.

Properties of (Se,S)-based chalcogenide glass films, and an application to a holographic supermicrofiche.

In a (Se,S)-based chalcogenide glass system, the optical property, such as transmission and refractive index, changes reversibly within amorphous phase when the sample is heated and light irradiated. The refractive index in the light-irradiated state is larger than that in the heated state, and the amount of change Deltan reaches 0.05 ~ 0.1 in the visible wavelength region. The merits of this glass system as a recording material are high resolving power and rewritability. As an application, a rewritable holographic supermicrofiche, which is partially refreshable, and its experimental system are given. Characteristic features of this material as applied to an information retrieval system are discussed.

New application of Se‐Ge glasses to silicon microfabrication technology

A selective etching effect due to photoexposure of Se‐Ge glass films was found. The possibilities of applying this phenomenon to the patterning of layers for silicon device processing and for the fabrication of photomasks were investigated. The results showed that the Se‐Ge glass has certain advantages in these applications.

High‐power, high‐efficiency 1.3 μm superluminescent diode with a buried bent absorbing guide structure

A superluminescent diode (SLD) operating in the 1.3 μm wavelength region has been fabricated by the liquid phase epitaxial growth technique. Lasing is effectively suppressed by incorporating an unpumped buried bent guide structure for SLD operation. Devices with an antireflection coating on the front facet emit a high optical power of 11.5 mW at an injection current of dc 200 mA. The Fabry–Perot mode has been sufficiently suppressed over the entire emission spectral bandwidth of 40 nm. The transverse mode is stable and a beam divergence of 48°×33° has been achieved. A coupling power of 1 mW was achieved for the 1.9% Δn, and 2.8‐μm‐diam core single‐mode fiber by butting.

InP/GaInAsP Buried Heterostructure Lasers of 1.5 µm Region

The buried-heterostructure, in which the quaternary active layer is completely surrounded by InP crystal, has been realized in 1.5 µm region by low temperature liquid phase epitaxial growth. Low threshold current of 25 mA under CW operation was achieved at 26°C. This is the lowest value so far reported on the InP/GaInAsP laser in 1.5 µm wavelength region.