Untitled record

PATENT

FRENCH REPUBLIC MINISTRY

INDUSTRY AND ENERGY

SERVICE Gr. 12. - Cl. 6. N ° 1.037.293 of INDUSTRIAL PROPERTY __

Dry rectifier with electrical control and its manufacturing process. '··

Said company: LICENTIA PATENT-VERWALTUNGS G. mb H. residing in

Requested on May 19, 1951, at 9^h 55^m, in Paris.

Issued April 29, 1953. - · Posted September 15, 1953.

Attempts have been made to make electrically controllable dry rectifiers by placing a control grid between two electrodes in a manner analogous to that which is done in high vacuum electronic tubes. These attempts did not lead to any practical results, although a certain control effect was observed. Extensive tests have shown that practically usable command or control can be obtained when the control electrode is placed in the circuit in such a way that the space charge layer forms in front of it, when connected to an appropriate voltage. , prevents current crossing. In electrically controllable dry rectifiers comprising a semiconductor substance with an excess conductive nature, this control effect occurs when the control electrode is brought to a negative potential with respect to its surroundings. In a controlled dry rectifier comprising a semiconductor substance with a deficient conductive character, the same effect is obtained by a positive control potential.

In the electrically controllable dry rectifier according to the invention, in which the space charge layer is used for control, the control electrode is advantageously made, at least in its part adjacent to the semiconductor substance, from a deficient conductor when the semiconductor substance has an excess conductive character. Conversely, in a dry rectifier comprising a semiconductor substance with a deficient conductive nature, the control electrode is produced, in its part adjacent to the semiconductor substance, in an excess conductor. Consequently, for the sake of brevity, the invention is explained in the following only in its application to dry rectifiers comprising a semiconductor substance of excess conductive nature. The control action is in fact always obtained in a similar manner by applying the teaching of the invention with a semiconductor substance with a deficient conductive nature, when one places in the rectifiers described in the places comprising a semiconductor substance with excess conductive character, parts made of a deficient conductive matter. Because the control electrode is chosen in its part adjacent to the semiconductor substance in a material which has the opposite conductive nature of the semiconductor substance, the result is obtained which can be connected to the electrode much higher voltage than in control electrode devices which have a mixed electronic or metallic conductive character.

It is particularly advantageous to provide, preferably by vaporization, the semiconductor substance on a non-conductive support in a layer thickness which is obtained by the thickness of the space charge layer occurring in the extreme case in front of the electrode. during the inspection. With this choice of the thickness of the semiconductor substance, a control action determined in. presence of minimum resistance.

In order that the resistance is as low as possible and that the dimensions of the control electrodes, or of their distances and of the other electrodes, are not too small, it is advantageous to use a semiconductor substance whose mobility of support of charge is greater than -¹⁰ and whose concentration of

V / cm disturbing points is so small that the thickness of the space charge layer occurring in extreme cases when checking in front of the electrode can reach the thickness of the semiconductor substance. Such large layer thicknesses are easily obtained when using a semiconductor substance whose concentration of disturbing points is lower than 5.10¹⁵/ cm³.

For the manufacture of controllable dry rectifiers according to the invention, it is convenient in many cases to transform the substance

- 41200

Booklet price: 100 francs.

- 2 - [1.037.293] semiconductor at its part adjacent to the control electrode locally so that it is distinguished from the surrounding by an opposite conductive character.

Embodiments of dry rectifiers according to the invention are represented, by way of examples, by the appended schematic drawing.

The metal electrodes 2, 3 are placed on a non-conductive support 1, for example made of glass or quartz and the semiconductor substance 4 is placed on these electrodes. The metallic conductor 5 going to the control electrode can be placed on the same side of the semiconductor substance as the electrodes 2 and 3, as shown in fig. 1, but the conductor 5 can also be provided on the side, as shown in FIG. 2. The actual control electrode is formed by a layer 6, which is adjacent to the semiconductor substance 4 and which has an inverse conductive nature therefrom. In some cases, additional losses occur at electrodes 2 and 3 and these losses must be taken into account when calculating the dimensions of these electrodes. If, for example, due to a rectifier effect occurring, the transition to electrode 2 implies losses which are greater than those occurring at electrode 3, it is advisable to establish this electrode larger than the electrode 3, or else to give the two electrodes the dimensions which are necessary for the passage of the current to the electrode 2. In the embodiments according to FIGS. 3 and 4, the electrode 2 is chosen for this reason to be larger than the electrode 5. It is particularly advantageous to constitute the electrodes in the form of circular surfaces or circular rings which surround themselves concentrically with each other, as shown in fig. 4.

If the flow of current must be controlled in dependence on several variable potentials, in the dry rectifier controlled according to the invention, between the electrodes 2 and 3, a corresponding number of control electrodes 5, 6 is provided, as indicated. in fig. 5.

Since the manufacture of the electrodes or of the transition layers adjacent to the latter of the semiconductor substance, which must have certain properties, requires in some cases a difficult working operation, it is advantageous in dry rectifiers which must present several controllable current paths separately side by side, make the arrangement as shown in fig. 6, so that the current paths have in common separate electrodes. In the exemplary embodiment, the electrode 2 is used both for the current path influenced by the control electrode 5, 6 and going to the electrode 3, and also for the current path influenced by the electrode 5 ', 6' and going to the 3 'electrode.

Since the control action can be obtained with voltages as low as possible without the resistance for the current flow of the dry rectifier according to the invention being too large, it is advantageous, as shown schematically in FIGS. 7 and 8, to give the semiconductor substance in its part 7, captured during the control by the space charge layer located in front of the control electrode, a smaller section than at the rest of the current path.

The same result can be obtained from the fact that at least the control electrode is divided into several parts coupled in parallel, separated from each other by thin layers of the semiconductor substance. Fig. 9 shows an embodiment of such an arrangement comprising a control electrode 5, 6 formed in the form of a layer.

Several thin layers of the semiconductor substance comprising the electrodes relating thereto can be applied directly to one another, preferably by alternating vaporization of semiconductor substance and electrode material on a non-conductive support, as indicated in the fig. 10, in which the broken lines 8 designate the limits of the various layers of semiconductor applied successively.

The manufacture of electrically controllable dry rectifiers according to the invention can be carried out by applying the semiconductor substance to a non-conductive support. It is then necessary to bring the support to a high temperature if it is therefore necessary to obtain a better modification of the applied substance. The electrodes can be applied by spraying, spraying or printing on the non-conductive support before the spraying of the semiconductor substance.

These electrodes are advantageously provided, already before the supply of the semiconductor substance, with conductors, so that the semiconductor substance is not damaged or adversely modified during the supply of the conductors.

For the production of a control electrode, which consists, at least in its part adjacent to the semiconductor substance, of a deficient conductor, the semiconductor substance in this part can be modified as desired by subsequent transformation . One can, for example, connect the semiconductor substance, preferably at temperature ο

considerably high, locally at a high voltage to obtain a non-homogeneous transformation of this kind and / or bring it into contact with substances, so that it differentiates in the environment of its specially treated parts with regard to its conductive nature of the rest of the untreated semiconductor substance. Particularly good results are obtained when the semiconductor substance reverses its conductive character in a region locally limited by these treatments.

Electrically controllable dry rectifiers, in which the semiconductor layer must have a smaller thickness near the control electrode, can be manufactured according to the vaporization process, since a layer of weaker is applied here. thickness than in the rest, by permanently or temporarily preventing deposition or by a vapor guide of appropriate direction. But, under certain conditions, it is simpler to bring the semiconductor substance firstly under an equal layer thickness and to remove it partially thereafter, for example by mechanical means, near the electrode. control, to locally reduce the thickness of the layer. This process can be carried out in a particularly simple way by first completely removing the semiconductor substance at this location and then affixing again a very thin layer of semiconductor substance. This process is explained using fig. 11. The groove 9 is dug into the applied semiconductor layer 4 using mechanical or chemical means. Then the semiconductor substance is again applied in a very thin layer 10. In this case, it is not necessary to limit the new vaporization to the width of the groove 9. On the contrary, it is generally advantageous to reinforce layer 4 everywhere with layer 10. The thin layer 10 of semiconductor substance applied afterwards must, as far as possible, have a lower concentration of disturbing points than the semiconductor substance 4 applied in a thick layer. Finally, the conductors 5 of the control electrode are applied to the thin layer 10 of semiconductor substance applied afterwards to the location of the groove, so that the current path in the surroundings of the control electrode extends completely into thin layer 10.

As an example of a semiconductor substance with an excess conductive nature, which is particularly suitable for the manufacture of dry rectifiers according to the invention, mention is made of germanium producing disturbing points, firstly with the addition of nitrogen, then in fl.037.293] addition with additions of phosphorus, arsenic and antimony. Selenium with halogen additions or silicon with boron and / or oxygen additions also give good results as semiconductors with a deficient conductive nature.

It is advisable to manufacture the semiconductor layer in a substance whose conductivity is greater than that of the control electrode. For example, germanium with nitrogen is suitable for this purpose as a semiconductor substance with excess conductive character and selenium with halogen additions is suitable as a control electrode with deficient conductive character.