Kazuhito FURUYA Kenji KURISHIMA Saed SAMADI
This letter describes theoretical characteristics of the electron diffraction transistor and its inverter circuit. The electron wave diffraction due to a transverse potential grating is analyzed taking thermally induced dispersions into account. The switching time is estimated as 0.4 ps at 77 K.
Yasuyuki MIYAMOTO Chiaki WATANABE Masashi NAGASHIMA Kazuhito FURUYA Yasuharu SUEMATSU
Fabrication of GaInAsP/InP heterostructure lasers for 1.5 µm wavelength region by organometallic vapor phase epitaxy are discussed. Results of growth conditions, which were experimentally found important to obtain the low threshold current density (1 kA/cm2) comparable with LPE at 1.5 µm lasing oscillation are reported, such as gas switching at hetero-interfaces, maintenance of constant temperature over the growth of all layers, selection of carrier gas and doping conditions. Furthermore, OMVPE device techniques for buried heterostructure laser operating at CW condition are described. Fabrications and characterization of quantum well structure are also reported.
Yasuyuki MIYAMOTO Ryo NAKAGAWA Issei KASHIMA Masashi ISHIDA Nobuya MACHIDA Kazuhito FURUYA
The feasibility of a new transistor structure was demonstrated through an experimental observation of current gain and voltage gain. The proposed transistor structure is a hot electron transistor without a base layer to minimize scattering. Electron emission from the emitter is controlled using positively biased Schottky gate electrodes located on both sides of the emitter mesa. Monte Carlo simulation shows an estimated delay time of 0.17 ps and low gate leakage current with open-circuit voltage gain over unity. To confirm the basic operation, the device with a 25 nm wide emitter was fabricated. To obtain saturated current-voltage characteristics, the emitter was surrounded by gates and parasitic regions were eliminated by electron beam lithography. The observed open-circuit voltage gain was 25. To obtain a low leakage current, an electron energy smaller than the Γ-L separation was necessary to maintain the ballistic nature of the electron. When the gate-emitter voltage was 0.8 V, the gate leakage current was only 4% of the collector current. Thus voltage amplication and current amplification were confirmed simultaneously.
Tomonori SEKIGUCHI Kazuhito FURUYA
The potential distribution around a linear array of donor atoms in a semiconductor crystal is calculated, approximating the linear array by a continuous line charge. Two methods are used for the analysis. One is the self-consistent calculation of Poisson's equation and the effective mass Schrödinger's equation, and the other is the Thomas-Fermi approximation. Results of both methods agree very well, and it is shown that it is possible to form a potential distribution as fine as the electron wavelength by appropriate arrangement of the impurity atoms. Arrays of impurity atoms therefore can act as buiding elements for future electron wave devices.
Chiaki WATANABE Satoru KINOSHITA Kazuhito FURUYA Yasuyuki MIYAMOTO
GaInAs/InP MOSFETs were fabricated by organometallic vapor phase epitaxy (OMVPE) for the first time to obtain an effective channel mobility of 900 cm2/Vs comparable to the best data by other growth techniques. For the MOS structure, a native oxide layer was formed by low-temperature (220) oxidation technique using water. Due to potentially high uniformity, OMVPE MOSFET technique could be very attractive in the optoelectronic integrated circuits(OEIC) for optical communication.
Masaki TAKAKUWA Kazuhito FURUYA
The minimum transferable linewidth by X-ray is derived using waveguide analysis. The minimum width is determined by the refractive index of the absorber and does not depend on the X-ray wavelength. Therefore there is an optimum mask aperture size which provides the minimum linewidth. By using Au as the absorber, 8 nm linewidth is attainable.
Yasuyuki MIYAMOTO Shinnosuke TAKAHASHI Takashi KOBAYASHI Hiroyuki SUZUKI Kazuhito FURUYA
We investigated collector current spreading in InGaAs single heterojunction bipolar transistors (SHBTs) having a collector thickness of 75 nm. SHBTs were fabricated with three different emitter widths -- 200, 400, and 600 nm -- and the highest cutoff frequency that was obtained was 468 GHz. The relationship between the current density at the highest cutoff frequency and the emitter width could not be used to estimate the current spreading because it was independent of the collector-base voltage. However, the relationship between the current density with the increase in the total collector-base capacitance and the emitter width indicates current spreading in the collector. The current spreading was estimated to be approximately 90 nm.