Photo-transistor in MOS thin-film technology and method for production and operation thereof
AssigneeSiemens Aktiengesellschaft
InventorsArmin Wieder, Lothar Risch
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Abstract
A photo-transistor in MOS thin-film technology operable with alternating voltages is comprised of a semiconductor body (3) composed of polycrystalline silicon having source (4) and drain (5) zones therein spaced apart by an undoped channel region (13) and having a gate electrode (1, 10) separated from the semiconductor body (3) by a SiO.sub.2 layer (2) produced by thermal oxidation. These phototransistors are easily and reproducably produced and are characterized by low threshold voltages and a good transistor characteristic curve. Thus, these photo-transistors are well suited for use as sensor elements, opto-couplers, time-delay elements and as photo-transistors in VLSI circuits.
Claims8
A method of operating a photo-transistor in MOS thin film technology, comprising steps of:
- (a) providing the MOS photo-transistor as
- (1) a semiconductor body comprising polycrystalline silicon having a source zone and drain zone located therein and spaced from one another by an undoped channel region,
- (2) a gate electrode formed of polycrystalline silicone positioned at and separated from said semiconductor body by an SiO.sub.2 layer generated on the silicon semiconductor body by thermal oxidation, and
- (3) a high defect density boundary region between the semiconductor body and the SiO.sub.2 layer;
- (b) applying an alternating voltage to the gate and applying an operating voltage between the source and drain zones;
- (c) exposing the photo-transistor to varying light amplitudes to cause variations in drain current;
- and
- (d) the photo-transistor being operable with the gate voltage lying anywhere in a range from 100 Hz to 1 Mhz.
A method of operating a photo-transistor in MOS thin film technology, comprising steps of:
- (a) providing the MOS photo-transistor as
- (1) a semiconductor body comprising polycrystalline silicon having a source zone and drain zone located therein and spaced from one another by an undoped channel region,
- (2) a gate electrode formed of polycrystalline silicon positioned at and separated from said semiconductor body by an SiO.sub.2 layer generated on the silicon semiconductor body by thermal oxidation, and
- (3) a high defect density boundary region between the semiconductor body and the SiO.sub.2 layer;
- (b) applying an alternating voltage to the gate and applying an operating voltage between the source and drain zones;
- (c) with no light exposure on the photo-transistor, substantially no drain current flows;
- and
- (d) with increasing light exposure on the photo-transistor, more and more defects in the boundary region are filled and a surface potential associated with the boundary region follows the alternating gate voltage faster and faster.
A method of operating a photo-transistor in MOS thin film technology, comprising steps of:
- (a) providing the MOS photo-transistor as
- (1) a semiconductor body comprising polycrystalline silicon having a source zone and drain zone located therein and spaced from one another by an undoped channel region,
- (2) a gate electrode formed of polycrystalline silicon positioned at and separated from said semiconductor body by an SiO.sub.2 layer generated on the silicon semiconductor body by thermal oxidation, and
- (3) a high defect density boundary region between the semiconductor body and the SiO.sub.2 layer;
- (b) applying an alternating voltage to the gate and applying an operating voltage between the source and drain zones;
- and
- (c) with light exposure on the photo-transistor, operating the photo-transistor at frequencies greater than 10 kHz.
A method of operating a photo-transistor in MOS thin film technology, comprising steps of:
- (a) providing the MOS photo-transistor as
- (1) a semiconductor body comprising polycrystalline silicon having a source zone and drain zone located therein and spaced from one another by an undoped channel region,
- (2) a gate electrode formed of polycrystalline silicon positioned at and separated from said semiconductor body by an SiO.sub.2 layer generated on the silicon semiconductor body by thermal oxidation, and
- (3) a high defect density boundary region between the semiconductor body and the SiO.sub.2 layer;
- (b) applying an alternating voltage to the gate and applying an operating voltage between the source and drain zones;
- and
- (c) the alternating voltage applied to the gate being at least 10 kHz and having a potential between 0 to 10 volts.
Dependencies are inferred from the claim text.