1. A silicon based semiconductor device comprising:
a silicon based substrate;
a channel region in the silicon based substrate for carrying a device current consisting of charge carriers between a source region and a drain region;
a gate region for receiving a gate bias voltage to control a density of said charge carriers in said channel region available for said device current;
a trapping region located proximate to said channel region, said trapping region being configured for trapping charge carriers and altering said density of charge carriers in said channel region;
wherein said density of charge carriers in said channel region available for said device current is also controllable by a drain bias voltage applied to said drain region, such that said drain bias voltage can reduce said density of charge carriers and turn off the silicon based semiconductor device.
2. The silicon based semiconductor device of claim 1, wherein said channel exhibits negative differential resistance.
3. The silicon based semiconductor device of claim 2, wherein conduction in said channel can be continuously and dynamically varied between a negative differential resistance mode and a non-negative differential resistance mode.
4. The silicon based semiconductor device of claim 1, wherein said trapping region is configured such that said charge carriers are trapped only temporarily and such that a continuous trapping and de-trapping mechanism is set up between said trapping layer and said channel.
5. The silicon based semiconductor device of claim 1, wherein a threshold voltage of the silicon based semiconductor device is controlled by said drain bias voltage.
6. The silicon based semiconductor device of claim I wherein an amount of charge carriers trapped by the charge trapping region is controlled by said drain bias voltage.
7. A metal-insulator-semiconductor field-effect transistor (MISFET) comprising:
first conductivity type doped source and drain regions formed in the surface of a semiconductor substrate and separated by a second conductivity type doped channel region, said second conductivity type being opposite to said first conductivity;
a gate formed over and electrically insulated from said channel region by a gate dielectric, which gate dielectric includes a charge trapping layer;
said charge trapping layer being located near an interface with said second conductivity type channel region and being configured to trap charge and cause a threshold voltage of the MISFET to be significantly altered in a dynamic and reversible manner in response to an adjustable bias voltage applied to the MISFET;
wherein said adjustable bias voltage is not a program andor an erase cycle.
8. The MISFET of claim 7 wherein a negative differential resistance characteristic is achieved by rapid trapping and de-trapping of electrons to and from said charge trapping sites in said charge trapping layer.
9. The MISFET of claim 7 wherein said charge trapping layer includes charge-trapping sites consisting of one or more islands of metal or semiconductor embedded in said gate dielectric.
10. The MISFET of claim 7 wherein said charge trapping layer comprises silicon nitride.
11. The MISFET of claim 7, wherein said adjustable bias voltage is applied to said first conductivity type source and drain regions.
12. The MISFET of claim 7, wherein a trapping mechanism by said charge trapping layer can be selectively disabled by applying a separate bias voltage to a body region portion of the MISFET.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of producing a porous glass preform using a porous glass preform production apparatus with a reaction vessel including an upper deposition chamber having a first air supply inlet in a first wall and an exhaust outlet in a second wall opposing the first wall, a lower deposition chamber having a second air supply inlet and connected to the upper deposition chamber by a connection opening on a floor of the upper deposition chamber, and a top chamber disposed on top of the upper deposition chamber and adapted to lift and store a porous glass preform formed by deposition, the method comprising:
supplying raw materials for glass, a combustible gas, and a combustion supporting gas to burners disposed in the apparatus; and
depositing glass microparticles generated by a flame hydrolysis reaction of the glass raw materials to produce a porous glass preform such that, during deposition, the floor of the upper deposition chamber is disposed at a height between a lower end of a straight body part and a deposition tip of the porous glass preform and a regular airflow passes through the connection opening from the lower deposition chamber to the upper deposition chamber, wherein
an angle of elevation \u03b8 from an upper end of the exhaust outlet to an upper end of the first air supply inlet satisfies the expression 5 degrees\u2266\u03b8\u226650 degrees,
the second wall includes a substantially vertical wall segment above the exhaust outlet and facing the first air supply inlet, and
the wall segment extends from the upper end of the exhaust outlet to a ceiling of the upper deposition chamber.
2. The method according to claim 1, wherein 0.05\u2266BA\u22660.6, where A is an aperture diameter of the connection opening and B is a diameter of the porous glass preform passing through the connection opening.
3. The method apparatus according to claim 1, wherein a distance from a center of the connection opening to an inner wall of the upper deposition chamber is A or more, where A is an aperture diameter of the connection opening.
4. The method according to claim 1, wherein a distance from a center of the connection opening to an inner wall of the lower deposition chamber is 0.7 A or more, where A is an aperture diameter of the connection opening.
5. The method according to claim 1, wherein an inner surface of the connection opening is processed by chamfering or processed to have a curved surface.
6. The method according to claim 1, wherein the connection opening has a structure separable from the floor of the upper deposition chamber.
7. The method according to claim 1, wherein gas supplied through the air supply inlets is ambient air which has been passed through a filter.
8. The method according to claim 1, further comprising controlling pressure inside the reaction vessel using an automated pressure controller installed downstream from the exhaust outlet.