GB1096735A - Improvements in or relating to opto-electronic circuit elements - Google Patents

Abstract

<PICT:1096735/C4-C5/1> <PICT:1096735/C4-C5/2> An opto-electronic circuit element 215, Fig. 1, comprises a first recombination radiation source 201 irradiating a photo-sensitive semi-conductor 202, and a second radiation source 205, whereby the effect of the first source on the semi-conductor 202 may be controlled. The second source either irradiates the semi-conductor 202 or a filter 206. The circuit element may be used for amplifying or logic applications. Embodiments in which both sources irradiate the detector.-The detector is a block 1, Fig. 2, of oxygen doped N-type GaP or AlP with a P region 3 of Zn diffused in to form a P-N junction 4. The contacts 5 and 6 alloyed to the P and N region are respectively Au + 4% w/w Zn and Sn. This detector has an energy level intermediate the valence and conduction bands. The source 10 of radiation which is only capable of causing the transition from the valence band to the intermediate level, comprises a GaAs or InP body 11 which is of N-type and has an alloyed contact 12 of In with 3% w/w Zn to form a recrystallized P region 14. The contact 18 is of alloyed Sn. The source 20 of radiation capable of causing the larger transition from the intermediate level to the conduction band comprises a block of P type GaP doped with Zn and O. An Sn contact is alloyed in to the block to form a recrystallized N region 24, the ohmic contact 23 being of alloyed Au + 4% w/w Zn. In the embodiment of Fig. 4 (not shown), the radiation source 20 and the detector 1 may be formed in the same semi-conductor body, the contacts 15 and 23 being replaced by a single contact, and in Fig. 6 (not shown) all three components are formed in a single unit by vapour depositing GaAs on GaP. Contacts 6 and 13 are then common. In the embodiment of Fig. 7 (not shown), the detector comprises P type GaP doped with Cu. The N region 83 is formed by recrystallization when the Sn contact 84 is alloyed in. The contact of 86 is of alloyed Au + 4% w/w Zn. This detector has an acceptor level between the valence and conduction bands which has little effect on the recombination of minority carriers produced by radiation from source 90 by band to band transitions. Radiation from source 100 lifts electrons from the valence band to the acceptor level providing holes which reduce the minority carrier lifetime, and by this means source 100 controls the response of the detector to source 90. The sources 90 and 100 are similar to source 20 except that for source 90 GaP is doped with Zn only. The light sources may be operated as injection recombination lasers and may be combined with the detector in a single semi-conductor body. Embodiments in which the filter is used.-The filter may comprise GaP doped with Zn and O to produce an intermediate level between the valence and conduction bands. If then the radiation from source 200 is capable of effecting only the transition to or from the intermediate level, radiation from the source 204 which is capable of effecting the other transition will increase the absorption of radiation from source 200. If the intermediate level is normally full, the sources are interchanged so that when source 200 empties the intermediate level, radiation from source 204 is absorbed in refilling it. The surface of the semi-conductor bodies may have anti-reflection coatings.