Characteristic order over distances of 15–30 A is indicated by various experiments on covalent non-crystalline solids. The data are reviewed and detailed structural models are developed containing 30–1000 atoms.

Topology of covalent non-crystalline solids II: Medium-range order in chalcogenide alloys and ASi(Ge)

Chemical vapor deposition (CVD) of silicon carbide (SiC) onto SiC{0001} substrates and its device applications are reviewed. Polytype-controlled epitaxial growth of SiC, which utilizes step-flow growth on off-oriented SiC{0001} substrates (step-controlled epitaxy), is proposed, and the detailed growth mechanism is discussed. In step-controlled epitaxy, SiC growth is controlled by the diffusion of reactants in a stagnant layer. Critical growth conditions where the growth mode changes from step-flow to two-dimensional nucleation are predicted as a function of growth conditions using a model describing SiC growth on vicinal {0001} substrates. Step bunching on the surfaces of SiC epilayers, nucleation, and step-dynamics are also investigated. The high quality of SiC epilayers was elucidated through low-temperature photoluminescence, Hall effect, and deep level measurements. Excellent doping controllability over a wide range was obtained by in situ doping of a nitrogen donor and aluminum/boron acceptors. Recent progress in SiC device fabrication using step-controlled epitaxial layers is presented. The intrinsic potential of SiC is demonstrated in the excellent performance of high-power, high-frequency, and high-temperature devices, which will develop novel electronics.

Step-controlled epitaxial growth of SiC: High quality homoepitaxy

Silicon molecular beam epitaxy

Deformation of the crystal lattice of layers of GaxIn1−xAs (0.5 < x < 1.0) grown onto GaAs substrates by a chemical vapor deposition process was investigated. For this study, Ga and In were transported as chlorides with HCl and AsH3 was the source of As. It was observed that the lattice constant along the direction of the film thickness was larger than that along the surface. This fact indicates that the crystal lattice of GaxIn1−xAs is compressed along the substrate surface as a result of lattice mismatch. The influence of both the composition of the epitaxial layers and the crystal plane of the substrate surface on the degree of this deformation was investigated. It was also found that the epitaxial orientation grew inclined to the substrate crystal when the crystal surface of the substrate was {100} or {110}.

Structure of vapor‐deposited GaxIn1−xAs crystals

Anisotropic lateral growth in GaAs MOCVD layers on (001) substrates

The effects of light irradiation on crystal growth were investigated in the vapor epitaxial growth of silicon. It was observed that the activation energy of crystal growth decreased with light irradiation. The magnitude of the decrease was 2.1 kcal/mole under the typical experimental condition in an rf heating reactor. Crystal growth was carried out at a temperature lower than that used in the conventional epitaxial method, and the crystal quality of the grown layers was found to be better in the case with light irradiation than that without irradiation. The above results suggest that light irradiation techniques can be used for reducing the degradation of impurity distribution by decreasing the growth temperature. At present, selective crystal growth according to an irradiation pattern can be realized. It is expected that epitaxial growth with light irradiation can be applied to a selective growth process.

Epitaxial Growth with Light Irradiation

Silicon epitaxial growth

Defect-free nucleation of silicon on {111} silicon surfaces

A field effect transistor comprises a semiconductor channel, a source and a drain electrode formed at the opposite ends of the channel and a gate electrode provided on the side of the channel. The channel has a small impurity density and therefore the depletion layer extending from the gate goes deep into the channel to substantially close the conductive portion of the channel even in the absence of a gate voltage. The drain current will not flow where the drain voltage is below a certain threshold voltage, and will flow where the drain volage is above the threshold voltage exhibiting a linear resistance characteristic. This drain-current to drain-voltage characteristic simulates the anode-current to anode-voltage characteristic of the triode vacuum tube very closely.

Takeshi Terasaki

Papers

Epitaxial Growth with Light Irradiation

Silicon epitaxial growth

Defect-free nucleation of silicon on {111} silicon surfaces

Field effect semiconductor device having an unsaturated triode vacuum tube characteristi

Layer growth in silicon epitaxy