In the past several years, research in each of the wide‐band‐gap semiconductors, SiC, GaN, and ZnSe, has led to major advances which now make them viable for device applications. The merits of each contender for high‐temperature electronics and short‐wavelength optical applications are compared. The outstanding thermal and chemical stability of SiC and GaN should enable them to operate at high temperatures and in hostile environments, and also make them attractive for high‐power operation. The present advanced stage of development of SiC substrates and metal‐oxide‐semiconductor technology makes SiC the leading contender for high‐temperature and high‐power applications if ohmic contacts and interface‐state densities can be further improved. GaN, despite fundamentally superior electronic properties and better ohmic contact resistances, must overcome the lack of an ideal substrate material and a relatively advanced SiC infrastructure in order to compete in electronics applications. Prototype transistors have been fabricated from both SiC and GaN, and the microwave characteristics and high‐temperature performance of SiC transistors have been studied. For optical emitters and detectors, ZnSe, SiC, and GaN all have demonstrated operation in the green, blue, or ultraviolet (UV) spectra. Blue SiC light‐emitting diodes (LEDs) have been on the market for several years, joined recently by UV and blue GaN‐based LEDs. These products should find wide use in full color display and other technologies. Promising prototype UV photodetectors have been fabricated from both SiC and GaN. In laser development, ZnSe leads the way with more sophisticated designs having further improved performance being rapidly demonstrated. If the low damage threshold of ZnSe continues to limit practical laser applications, GaN appears poised to become the semiconductor of choice for short‐wavelength lasers in optical memory and other applications. For further development of these materials to be realized, doping densities (especially p type) and ohmic contact technologies have to be improved. Economies of scale need to be realized through the development of larger SiC substrates. Improved substrate materials, ideally GaN itself, need to be aggressively pursued to further develop the GaN‐based material system and enable the fabrication of lasers. ZnSe material quality is already outstanding and now researchers must focus their attention on addressing the short lifetimes of ZnSe‐based lasers to determine whether the material is sufficiently durable for practical laser applications. The problems related to these three wide‐band‐gap semiconductor systems have moved away from materials science toward the device arena, where their technological development can rapidly be brought to maturity.

Large‐band‐gap SiC, III‐V nitride, and II‐VI ZnSe‐based semiconductor device technologies

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

A II-VI compound semiconductor laser diode (10) is formed from overlaying layers of material including an n-type single crystal semiconductor substrate (12), adjacent n-type and p-type guiding lasers (14) and (16) of II-VI semiconductor forming a pn junction, a quantum well active layer (18) of II-VI semiconductor between the guiding layers (14) and (16), first electrode (32) opposite the substrate (12) from the n-type guiding layer (14), and a second electrode (30) opposite the p-type guiding layer (16) from the quantum well layer (18) Electrode layer (30) is characterized by a Fermi energy A p-type ohmic contact layer (26) is doped, with shallow acceptors having a shallow acceptor energy, to a net acceptor concentration of at least 1 x 1017 cm-3, and includes sufficient deep energy states between the shallow acceptor energy and the electrode layer Fermi energy to enable cascade tunneling by charge carriers

Blue-green laser diode

Beams of electrons and ions are now fairly routinely focused to dimensions in the nanometer range. Since the beams can be used to locally alter material at the point where they are incident on a surface, they represent direct nanofabrication tools. The authors will focus here on direct fabrication rather than lithography, which is indirect in that it uses the intermediary of resist. In the case of both ions and electrons, material addition or removal can be achieved using precursor gases. In addition ions can also alter material by sputtering (milling), by damage, or by implantation. Many material removal and deposition processes employing precursor gases have been developed for numerous practical applications, such as mask repair, circuit restructuring and repair, and sample sectioning. The authors will also discuss structures that are made for research purposes or for demonstration of the processing capabilities. In many cases the minimum dimensions at which these processes can be realized are considerably larger than the beam diameters. The atomic level mechanisms responsible for the precursor gas activation have not been studied in detail in many cases. The authors will review the state of the art and level of understanding of direct ion and electron beam fabrication and point out some of the unsolved problems.

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Gas-assisted focused electron beam and ion beam processing and fabrication

Advancing EDM through fundamental insight into the process

Continuous-wave operation in wide-gap II-VI semiconductor current injection laser diodes at room temperature has been demonstrated for the first time. Stimulated emission was observed at a wavelength of 523.5 nm with a threshold current of 45 mA (1.4 kA/cm2) from ZnCdSe/ZnSe/ZnMgSSe single-quantum-well (SQW) separate-confinement heterostructure (SCH) laser diodes.

Room temperature continuous operation of blue-green laser diodes

Continuous‐wave (cw) operation at temperatures up to 23 °C of an Al0.26Ga0.26In0.48P/Ga0.52In0.48P/ Al0.26Ga0.26In0.48P double heterostructure (DH) laser has been achieved for the first time. The threshold current was 160 mA at 20 °C for a device with a 10‐μm‐wide and 250‐μm‐long ion‐implanted stripe geometry. The emission wavelength was 671 nm during cw operation at 10 °C. To reduce thermal resistance to a heat sink, a dually stacked structure made of a thin (∼0.3 μm) p‐AlGaInP layer and a p‐Al0.76Ga0.24As layer was used as a cladding layer. The DH wafer was grown by atmospheric pressure metalorganic chemical vapor deposition.

Room-temperature continuous-wave operation of an AlGaInP double heterostructure laser grown by atmospheric pressure metalorganic chemical vapor deposition

Optical properties were investigated on the superlattices with a unit lattice period of (AlAs)n(GaAs)n (n=1–24) which were grown by atmospheric‐pressure metalorganic chemical vapor deposition. Raman spectroscopy indicated that superlattice structure is realized for each n without collapsing into alloys. Photoluminescence measurement indicated that the ultrathin‐layer superlattice (with n larger than 2) has a direct energy gap, which is in good agreement with a tight‐binding calculation.

Optical properties of (AlAs)n(GaAs)n superlattices grown by metalorganic chemical vapor deposition

At room temperature (296 K), continuous-wave (CW) operation of a blue laser diode has been achieved. The emission wavelength is 489.9 nm, and the threshold current and voltage is 93 mA (1.5 kA/cm2) and 6.3 V, respectively. The laser consists of a ZnCdSe/ZnSSe/ZnMgSSe single-quantum-well (SQW) separate-confinement heterostructure (SCH).

Continuous-wave operation of 489.9nm blue laser diode at room temperature

A new solution system consisting of , , and was found useful for etching wafers. This solution system can be divided into four regions a–d, according to etching characteristics. The boundaries between the regions are given by a mole ratio of to of about 2.3 and a mole fraction of of about 0.9 at room temperature. Rate‐limiting processes are: a, adsorption of (, ); b, diffusion of (, ); c, dissolution of oxidized products (, ); and d, adsorption of (,). Solutions in region a have a reproducible etching rate of 0.01–0.1 μm/min, which is useful for MESFET processing. Crystallographic etching is also available with solutions in region c.

Yoshifumi Mori

Papers

Room temperature continuous operation of blue-green laser diodes

Room-temperature continuous-wave operation of an AlGaInP double heterostructure laser grown by atmospheric pressure metalorganic chemical vapor deposition

Optical properties of (AlAs)n(GaAs)n superlattices grown by metalorganic chemical vapor deposition

Continuous-wave operation of 489.9nm blue laser diode at room temperature

A New Etching Solution System, H 3 PO 4 ‐ H 2 O 2 ‐ H 2 O , for GaAs and Its Kinetics