Stauffer Chemical Company

Lewis A Bunz

Rozalie Schachter

Marcello Viscogliosi

Paul M Raccah

Harvey B Serreze

Diego J Olego

Thin film field effect transistors utilize MP.sub.x as the active switched semiconductor where M is at least one alkali metal, P is at least one pnictide, and x ranges from 15 to infinity. Phosphorus is preferred as the dominant pnictide and potassium is preferred as the dominant alkali metal. The local order of the semiconductors may vary from an all parallel pentagonal tube-like structure to a layer-like puckered sheet structure. The all parallel pentagonal tube structure is preferred. Metal insulated semiconductor (MISFETS) and metal semiconductor (MESFETS) field effect transistors are disclosed. The semiconductor is preferably doped with up to approximately 1/2% nickel, iron, or chromium, to reduce the density of defect levels in the bandgap without increasing the conductivity. The semiconductors may be doped with 1/2-1% of the same metals to increase conductivity so as to provide normally ON devices. The regions of a semiconductor under the source and drain may be heavily doped with 2-3% of the same metals to provide good contact to the source and drain. Nickel is the preferred metal.

Sputtering method for making thin film field effect transistor utilizing

Pnictide thin films, particularly phosphorus, grown on III-V semiconductors, particularly InP, GaP, and GaAs, are amorphous and have a novel layer-like, puckered sheet-like local order. The thin films are typically 400 Angstroms thick and grown preferably by molecular beam deposition, although other processes such as vacuum evaporation, sputtering, chemical vapor deposition, and deposition from a liquid melt may be used. The layers are grown on the &lt;100&gt; &lt;110&gt;, and &lt;111&gt; surfaces of the III-V crystals. The pnictide layer reduces the density of surface states, and allows the depletion layer to be modulated, the surface barrier reduced, the electron concentration at the surface increased, and there is a decrease in the surface recombination velocity and an increase in the photoluminescence intensity. The layers may be utilized in MIS and Metalsemiconductor (Schottky) devices for example to insulate and passivate MISFETS, to passivate MESFETS, to reduce the surface current component of the reverse bias dark current in P-I-N and avalanche diodes, and to improve performance of opto-electronic devices such as light emitting diodes, lasers, solar cells, photo cathodes and photo detectors. The pnictide layer may be applied to intermetallic and compound semiconductors having a pnictide component. The pnictides may be phosphorus, arsenic, antimony or bismuth, or combinations thereof.

Passivation of InP by plasma deposited phosphorus

Thin film field effect transistors utilize MP.sub.x as the active switched semiconductor where M is at least one alkali metal, P is at least one pnictide, and x ranges from 15 to infinity. Phosphorus is preferred as the dominant pnictide and potassium is preferred as the dominant alkali metal. The local order of the semiconductors may vary from an all parallel pentagonal tube-like structure to a layer-like puckered sheet structure. The all parallel pentagonal tube structure is preferred. Metal insulated semiconductor (MISFETS) and metal semiconductor (MESFETS) field effect transistors are disclosed. The semiconductor is preferably doped with up to approximately 1/2% nickel, iron, or chromium, to reduce the density of defect levels in the bandgap without increasing the conductivity. The semiconductors may be doped with 1/2-1% of the same metals to increase conductivity so as to provide normally ON devices. The regions of a semiconductor under the source and drain may be heavily doped with 2-3% of the same metals to provide good contact to the source and drain. Nickel is the preferred metal. The insulating layer may be SiO.sub.2, Al.sub.2 O.sub.3, or Si.sub.3 N.sub.4, but is preferably P.sub.3 N.sub.5 to provide chemical continuity to the polypnictide semiconductor.

Thin film field effect transistors utilizing a polypnictide semiconductor

Amorphous and polycrystalline films of KP.sub.15 are formed by RF diode sputtering targets of KP.sub.15 and excess phosphorus in an argon phase. Substrate temperatures up to 280.degree.-300.degree. C. provide amorphous films. Higher temperatures provide microcrystalline or polycrystalline films. These films have high resistance and may be used as the insulator in MIS devices employing III-V semiconductors. Co-sputtering with nickel increases the conductivity of the films from approximately 10.sup.-10 (ohm-cm).sup.-1 to 10.sup.-2 (ohm-cm).sup.-1 ; only reduces the optical gap by 0.2 eV; and reduces the activation energy from 0.8 eV to 0.2 eV; the nickel content varying from 5-15%. Substrates include glass, silicon, tantalum, stainless steel, gallium phosphide and gallium arsenide, and glass metallized with metals such as titanium, nickel and aluminum. Double diode electrical characteristics have been observed in devices formed on metallized glass substrates having co-sputtered thereon thin film polyphosphides and nickel with nickel and titanium top contacts.

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Peekskill, NY, United States of America

Lewis A Bunz