| 摘要 |
<p>A threshold device (10,54,82) is provided which passes very little current when the voltage applied across it is below its threshold voltage and which can pass a large amount of current when the voltage applied across it exceeds that threshold. The threshold device comprises a common body (12,62) of deposited amorphous semiconductor material and two separate electrical contacts (18,19), each having a junction forming portion (20,21; 60,64; 52,65) in contact with the common body. The junction forming portions each form a junction (22,24) having a depletion region (26,28) in the semiconductor material of the common body. As a result, when a voltage is applied between the two contacts, one of the function is forward biased and the other is reverse biased. Both the spacing between the junctions and the electrical properties of the common body and the junctions are such that when the threshold voltage is applied between the contacts, the depletion region of the reverse biased junction extends all the way to the depletion region of the forward biased junction, greatly increasing the conductivity between said two contacts. The threshold voltage at which such a punch-through of the depletion regions occurs is less than the voltage required to cause avalanche breakdown across the reverse biased junction. Among other things, such threshold devices are used as isolation devices (54,82,92,94,102,104) for the individual pixels (42) of a light influencing display (40).</p> |
