Patent
1984-04-30
1986-09-23
James, Andrew J.
357 30, 357 58, 357 86, 357 20, H01L 2980
Patent
active
046138811
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a semiconductor photoelectric transducer.
BACKGROUND ART
Diodes are known as conventional semiconductor photoelectric transducers, such as a p-i-n photo diode and an avalanche photo diode proposed elsewhere by the present inventor, a bipolar photo transistor and so forth. High-sensitivity and high-speed photo transistors of low noise, in the form of a field effect transistor having a channel of a low impurity density or an intrinsic semiconductor and a static induction transistor (hereinafter referred to as the SIT) have already been disclosed by the present inventor in Japanese Pat. Applns. Nos. 86572/78 and 87988/78. Since they have very high-sensitivity and high-speed, their characteristics are far more excellent than those of the conventional bipolar photo transistor.
FIG. 1A shows a conventional semiconductor photoelectric transducer provided with a plurality of gates.
Reference numeral 1 indicates an n.sup.+ silicon substrate, 2 an n.sup.- layer of a low resistivity or an i layer of an intrinsic semiconductor which will ultimately serve as a channel, 3 a high impurity density first gate region reverse in conductivity type from the channellayer, 4 a high impurity density second gate region reverse in conductivity type from the channel, as is the case with the region 3, 5 a high impurity density region of the same conductivity type as the substrate 1, 7 and 10 electrodes for the substrate 1 and the high impurity density regions 5, respectively, which form a main current path of the channel, 9 a gate electrode for the second gate region 4, 8 a gate electrode for the first gate region 3, and 6 an insulating film layer or multilayer insulating film as of SiO.sub.2 or Si.sub.3 N.sub.4 which has known insulating and surface protecting functions for isolating the electrodes 7, 8 and 9.
FIG. 1B is a top plan view of FIG. 1A. This device can be formed to have a multi-channel structure.
FIGS. 1C and D show another conventional semiconductor photoelectric transducer, in which the second gate electrode 4 is provided in the form of a cross stripe. All reference numerals are the same as those used in FIG. 1A.
With the conventional semiconductor photoelectric transducers shown in FIG. 1, it is possible to obtain a normally-ON or normally-OFF function or a function intermediate therebetween by selecting the impurity density of the high resistivity layer 2, the distance Wg between the first and second gates 3 and 4 and the diffusion depth l of the gate. In FIG. 1, when the diffusion potentials of n.sup.+ n.sup.- p.sup.+ junctions formed between the main electrode region 5 and the first and second gates 3 and 4 through the channel layer 2, respectively, are selected to be V.sub.bi (5-3) and V.sub.bi (5-4), these values become equal. The reason is that the distances between the main electrode region 5 and the first and second gate regions 3 and 4 are equal, as shown in FIG. 1 and that the impurity density of the channel 2 is symmetrical around the main electrode region 5.
Accordingly, in the semiconductor photoelectric transducers provided with a plurality of gates as shown in FIGS. 1A to 1D, since carriers generated by an optical input 11 are stored in the first and second gates with substantially the same probability, it is difficult to separate the functions of the first and second gates.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor photoelectric transducer which permits the separation of the functions of the first and second gates.
Another object of the present invention is to provide a photo transistor which is arranged so that optically excited carriers are easy to store only in one of the gates and the other gate is used merely as means for providing a fixed potential, thereby essentially reducing the gate capacitance to provide for improved frequency characteristics.
The abovesaid objective is attained by a field effect transistor or static induction transistor type photoelectric transducer of the present inventi
REFERENCES:
patent: 3714522 (1973-01-01), Komiya et al.
patent: 4284997 (1981-08-01), Nishizawa
patent: 4317127 (1982-02-01), Nishizawa
patent: 4422087 (1983-12-01), Ronen
patent: 4459556 (1984-07-01), Nanbu et al.
patent: 4484207 (1984-11-01), Nishizawa et al.
James Andrew J.
Mintel William
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