Semiconductors and semiconductor materials with recent developments

Preparation of semiconductor materials

Semiconductors with predictable, reliable electronic properties are necessary for mass production. The level of chemical purity needed is extremely high because the presence of impurities even in very small proportions can have large effects on the properties of the material. A high degree of crystalline perfection is also required, since faults in crystal structure (such as dislocations, twins, and stacking faults) interfere with the semiconducting properties of the material. Crystalline faults are a major cause of defective semiconductor devices. The larger the crystal, the more difficult it is to achieve the necessary perfection. Current mass production processes use crystal ingots between four and twelve inches (300 mm) in diameter which are grown as cylinders and sliced into wafers.

Because of the required level of chemical purity and the perfection of the crystal structure which are needed to make semiconductor devices, special methods have been developed to produce the initial semiconductor material. A technique for achieving high purity includes growing the crystal using the Czochralski process. An additional step that can be used to further increase purity is known as zone refining. In zone refining, part of a solid crystal is melted. The impurities tend to concentrate in the melted region, while the desired material recrystalizes leaving the solid material more pure and with fewer crystalline faults.

In manufacturing semiconductor devices involving heterojunctions between different semiconductor materials, the lattice constant, which is the length of the repeating element of the crystal structure, is important for determining the compatibility of materials.[…]

Recent research activities on semiconductor:

• An Old Dream Fulfilled: Zinc Oxide As Semiconductor: Zinc oxide is a “jack of all trades” – thousands of tons are produced all over the world every year for a wide range of uses. Zinc oxide has been used for everything from a food additive to a sun screening agent. It is even a significant semiconductor, although the long-awaited breakthrough in this field is yet to come. Perfect doping -- important in the production of semiconductor devices -- is not yet possible. Researchers now a clearer understanding of why.[1]
• Bottoms Up: Better Organic Semiconductors For Printable Electronics: Researchers have learned how to tweak a new class of polymer-based semiconductors to better control the location and alignment of the components of the blend. Their recent results could enable the design of practical, large-scale manufacturing techniques for a wide range of printable, flexible electronic displays and other devices.[2]
• Creating Unconventional Metals: ‘Quantum Halfway House Between Magnet And Semiconductor Discovered’: The semiconductor silicon and the ferromagnet iron are the basis for much of mankind's technology, used in everything from computers to electric motors. Scientists now report that they have combined these elements with a small amount of another common metal, manganese, to create a new material which is neither a magnet nor an ordinary semiconductor.[3]
• Neutron Researchers Discover Widely Sought Property In Magnetic Semiconductor: Researchers have demonstrated for the first time the existence of a key magnetic property of specially built semiconductor devices that raises hopes for even smaller and faster gadgets that could result from magnetic data storage in a semiconductor material.[4]
• Single-crystal Semiconductor Wire Built Into An Optical Fiber: A process has been developed for growing a single-crystal semiconductor inside the tunnel of a hollow optical fiber. The new device will add new electronic capabilities to optical fibers, which are ideal media for transmitting many types of signals and which are used in a wide range of technologies that employ light, including telecommunications, medicine, computing, and remote-sensing devices.[5]
• First Semiconductor-based PET Scanner Demonstrates Potential To Aid In Early Diagnosis Of Disease: Evaluations of the first-ever prototype positron emission tomography brain scanner that uses semiconductor detectors indicate that the scanner could advance the quality and spatial resolution of PET imaging, according to researchers. Eventually, the technology could be used to provide early-stage diagnoses of other cancers, neurological disorders and cardiovascular disease; assess patients' responses to therapies; and determine the efficacy of new drugs.[6]