Methods and devices for detecting incident radiation are provided. The methods and devices use high quality single-crystals of photoactive semiconductor compounds in combination with metal anodes and metal cathodes that provide for enhanced photodetector performance.

A production apparatus for a metal oxide single crystal according to the present invention includes a crucible for housing a crystal raw material and a seed crystal, which has a first end and a second end, and in which the crystal raw material is disposed on a first end side, and the seed crystal is disposed on a second end side, a heater that heats the crucible, and a cooling rod, which has a third end and a fourth end, and in which the third end is provided in contact with or in proximity to the second end of the crucible so as to cool the second end by depriving the second end of heat.

A directional solidification furnace includes one or more movable cooling plates disposed beneath a crucible. In a first position, the cooling plates are free from contact with a crucible support positioned adjacent the crucible. In a second position, the cooling plates are in contact with the crucible support. A control system is used to control the amount of force exerted by the cooling plates against the crucible.

A heater comprises a plurality of zones with at least two zones having a variable power density gradient different from one another. The heater having zones of different variable power density gradients allows for controlling the heat output and temperature profile of the heater in one or more directions of the heater. The heater can be used, for example, to control the temperature profile in a vertical direction.

An investment casting apparatus includes a furnace having an opening, a mold support, and a multi-axis actuator connected with the mold support and configured to retract the mold support from the opening with multiple-axis motion. An investment casting method includes withdrawing, with multiple-axis motion, a mold through the opening of the furnace to solidify a molten metal- or metalloid-based material in the mold. The apparatus and method can be used to form a cast article that has a body formed of the metal- or metalloid-based material. The body has a multi-textured, single crystal microstructure.

Methods and systems for low etch pit density gallium arsenide crystals with boron dopant may include a gallium arsenide single crystal wafer having boron as a dopant, an etch pit density of less than 500 cm.sup.2, and optical absorption of 6 cm.sup.1 or less at 940 nm. The wafer may have an etch pit density of less than 200 cm.sup.2. The wafer may have a diameter of 6 inches or greater. The wafer may have a boron concentration between 110.sup.19 cm.sup.3 and 210.sup.19 cm.sup.3. The wafer may have a thickness of 300 m or greater. Optoelectronic devices may be formed on a first surface of the wafer, which may be diced into a plurality of die and optical signals from an optoelectronic device on one side of one of the die may be communicated out a second side of the die opposite to the one side.

A crucible for formation of a crystalline material by solidification by growth on seed, including a bottom, at least one side wall orthogonal to the bottom of the crucible, and at least two marks extending on the inner surface of the at least one side wall in an orthogonal direction to the bottom of the crucible, for materialising the position of at least one seed designed to be positioned at the bottom of the crucible, the seed including at least first and second surfaces orthogonal to the bottom of the crucible. The respective positions of at least two of the marks on at least one of the side walls define, in the crystalline material, a first cutting plane tangent to the first surface of the seed and a second cutting plane tangent to the second surface of the seed.

Methods and wafers for vertical gradient freeze 8 inch gallium arsenide (GaAs) substrates. In disclosed examples, vertical gradient freeze systems for forming gallium arsenide (GaAs) substrates having silicon as a dopant, the system includes a crucible to contain a GaAs liquid melt and seed material during a formation process; one or more heating coils arranged in a plurality of heating zones; and a pedestal to move relative to the crucible, the system operable to control heating of the plurality of heating zones and movement of the pedestal to form a single crystal GaAs substrate.

Methods and wafers for vertical gradient freeze 8 inch gallium arsenide (GaAs) substrates. In disclosed examples, vertical gradient freeze systems for forming gallium arsenide (GaAs) substrates having silicon as a dopant, the system includes a crucible to contain a GaAs liquid melt and seed material during a formation process; one or more heating coils arranged in a plurality of heating zones; and a pedestal to move relative to the crucible, the system operable to control heating of the plurality of heating zones and movement of the pedestal to form a single crystal GaAs substrate.

Provided is a Mg.sub.2Si single crystal in which generation of low-angle grain boundaries in the crystal is satisfactorily suppressed. A Mg.sub.2Si single crystal, wherein a variation in crystal orientation as measured by XRD is in a range of 0.020.