DE1941061C3 - Electron source with a semiconductor body - Google Patents

Description

3 4

According to the invention, this object is achieved by the gallium phosphide layer 4 is with a depth an electron source of the type mentioned acceptor contaminant material, such as. B. iron, dissolved, which is characterized in that a chromium or copper doped. The interaction of this first surface, opposite the second surface, between the electropositive cesium layer 5 and the semiconductor body * either a thin p-type 5 of the p-type gallium phosphide layer 4 has a zone that creates a flat acceptor level in: ation of the deep acceptor in the vicinity of the Boundary ionized acceptor contamination in a high concentration area between these layers results,
iru.ion contains and is considerably thinner than the cesium layer, which acts on the cesium layer 5; in-semiconductor body between the two surfaces, or the adjacent surface of the gallium phide layer 4, a metal of high discharge energy, which with the second io like a highly doped (ie, degenerate or almost deflated forms a Schottky barrier layer, arranged degenerate) p-type semiconductor material. The energy is, and that one of the thin p-zone or of the band structure of the dynode i is such that the electron barrier-independent device for generating in the conduction band of the semiconductor material containing the layer 4 or forming electrons in the conduction band of the semiconductor material the free lying overhead is provided. 15 area 6 of the cesium layer 5 with a residual energy

Both measures will be able to reach those in the line that are sufficient for them to achieve the

band of the semiconductor material of the semiconductor body overcome potential mountain on this surface and

the resulting electrons are prevented from being emitted by it.

Emission surface opposite side of the semiconductor D: e dynode 1 can thus be used as an electron multiplier

to diffuse k-'rpers and to recome there. secondary hemisphere compartments can be used.

so that the electron yield of the known electro- JaB now the exposed ob «, - laugh 6 of the cesium-

i-.enqueüen is improved. layer 5 with primary clones in: in the same direction as

Developments and refinements of the invention are indicated by the arrow 7. bombed. \ on

fertilizers are characterized in the claims. secondary electrons emitted from the surface 6 can

The idea of the invention will be referred to below with reference to a suitable electric field in the

'on exemplary embodiments with reference to the direction shown by the arrow 8 can be deducted.

Drawing explained in more detail: it shows the primary electrons can typically have energies in

Fig. 1 have the transverse tisansidit an a's secondary range of 300 to 1 OvM 10 eV,
emission dynode suitable, preferred! Execution If the thickness of the aluminum oxide substrate 2

form of the invention. 30 down to about 500 λ, one can use Dynode I

Fi ;: 2a is a schematic cross-sectional view of the secondary electron multiplier from

active part of the secondary transmission type shown in Fig. In this structure

emissionsdynodi and the primary electrons to the exposed one! '. surface

i ig. 2b shows a band model for the aluminum oxide layer or the substrate 2 shown in FIG. 2a

! "c -part part i'.r secondary emission dynode. 35 directs. They penetrate the aluminum oxide film 2

'nter the term used in the following and the beryllium layer 3 and thus achieve the ■ 1 iach-acceptor impurity! " of the exposed surface 6 of the band gap of the semiconductor material ratio cesium layer 5 emits! will. Since about 40
·:. generally flat Akzeplorn levels are generated, which are at 40% of the energy of the primary electrons that strike! - Passing the normal operating temperature of the electron source, the alumina and beryllium are practically completely ionized. layer is lost is a; el; uiv high energy of the

With the expression "Tiefakzeptonerimreinigunii" primary leak trons in the order of magnitude from -HKH) to

^: m means an acceptance contamination. the normal 50 () () eV is useful if the dynode 1 is used as a sol-

• - 'rather not at the operating temperature of the semiconductor 45 rather FraiiMnissionselt. stroiienver. cheat iellacher

body is ionized. Because with some special one.

. '-solenten temperature T a thermal energy of The beryllium layer 3 can typically have a thickness of

■ '/' electron volts (k is the Boltznmnn constant) have a few atomic diameters, and the thickness

is available. muli the lomation energy of a flowing gallium phid layer 4. the monocrystalline or

acceptable contamination greater than this value. 5 ° can also be polycrystalline, about 0.2 to

Preferably, low-cost pollution is avoided! Microns are 1

Only ionization materials of about 4 AT or more cause a heat treatment to remove beryllium

turns. Since the air of AT at room temperature of layer 3 by a short Strc-'kf (about 10 to 100 Λ)

t.r.X) K) is 0.026 cV, a 1 k-f.iccentor should be used. as diffused into the gallium phosphide layer 4 and

in an arrangement according to the invention, he thereby uses a thin, highly doped surface

det is, at barely any temperature, a lomsation energy region of the ρ'-type forms
of at least about 0.1 eV. Unranuuing the use of an Iicfacceptor

The SekuiHläremissionsdyMudi shown in FIG. in the (iulliuniphosphidschicht 4. as below

1 uses the principle of the negative electroncnaifi- will be explained in more detail,> m inside the

nity and has a substrate 2 made of aluminum oxide, 60 layer 4 an internal electric field (a drift field I.

on which there is a thin layer 3, which results in the electrons in the direction of

a flaeh acceptor contaminant material. how cesium moves 5 and thereby the external

z. B. Beryllium, on this Bery lliumschiciii 3 quantum yield of the Dynode 1 is increased,
there is a p-conducting semiconductor layer 4 from The mode of operation of the dynode 1 is now to hand

Gallium phosphide. To be explained in more detail on the gallium phosphide schielite 4 6 ₅ of FIGS. 2a and 2b. As in

a thin cesium sheet 5 is arranged, the partial sectional view of which is shown in FIG.

Thickness of the order of a few atoms- the active T: il of the dynode 1 holds the p-type

measure through! can lie. Gallium phosphide layer 4 and the cesium surface

5 6

Flat layer 5. A thin p 'area 21 is created by electrons in the conduction band of the semiconductor layer 4. The diffusion of beryllium from the layer 3 into the conduction band by secondary or metallic beryllium in the layer 4. I awmener / euuung. Generation of holes Ileklr> The total thickness /> of the layer 4 can typically / between new pairs by photons, by injection, duuii about 0.2 and 1 micron, while the thickness a '> tunnel effects or by another suitable 1, however ρ - region 21 approximately up HK) Λ amount IO, ti Ii direction have been introduced are, it may be less gewesentlieh ais the total thickness of the stops, in the direction / u pet animal I'missioiisoberfläche I 4. the lalbieiterschicht Di. ke r animal Caesiumscmcht 5 opposite surface to diffuse (where ti ic can be about 1 to H) Λ. Electrons can and cannot be recommended

The band model! for the active part of the DvihkY 1; m act more as charge carriers), namely through d.i-,

is shown in Fig. 2b, the vertical with I ig 2a presence of tier ρ layer 21. This layer 21 i-i

flees. The band gap / wipe the valence band as already mentioned, with a Flachak / eptor.

and the conduction band has the white /: '“. while like / B. Beryllium in high concentration. doii'T '

the ionization energy of the low acceptor pollution. Other I laehak / eptoren. like / ■■

(Iron, chromium or copper) in the gallium phosphide- 15 / ink oiler cadmium, can be used. The lom-a-

layer 4 has the value E _n . In the middle of the energetic energy of the beryllium as ac / eptorserunienn-

the valence band and the conduction band is in the man- agement is less than 0.020 eV. so that thesis Herν 11 ■■■ - ■ -

The model has an intrinsic line * - or intriii-ic-l. line ac / eptoren practically completely in Raumteinpetai '

/ osien. It is known that parts of the conductive layer have. are ionized iA7 "is ¹ at room tempei.i ';

in which the Fermi level is below the tier intrinsic line 20 0.026 cV). The highly doped layer 21 therefore stops d.i.

cherishes. p-line on. during parts of the stratum, in Fermitmeau in tier near ties upper edge * d * *

where the Fermi level is above tier! -itrin-.ie-l. line valence band, as in I ig. 2b is shown The * ι ·.! Ι

are η-conductive. resulting potential mountain 22 prevents the F.lektn; ie "·

With the ionization energy / ·. '"The Tiefak / eptorver- to reach the ρ -layer 21,

Impurity refers to the energy that each contaminates 25 Instead of a highly doped p-layer

reiniguncshaftstcllc must be granted. so that one of the necessary potential mountains can be used there:

Hole is created. one also bordering on the emission upperfMc ¹ . ■

The clektropositive cesium layer 5 presses the opposite surface of the Galliiimphosp] ■■: · '.

lower edge of the conduction band at tier emission -, - layer 4 cm suitable metal high exit area i

Provide the surface of the p-lite layer 4 on the Fermi 30 (instead of layer 3) so that a bulkhead! ■

ni \ eau. as shown in Fig. 2b. The exit barrier layer is formed, which is similar in Wc- ·

work ψ on the emission surface 6 can be defined preventing electrons from emitting,> K r

will diffuse away as the difference between the vacuum energy area. One for creating egg; ■

level and the Fermi level on this surface. metal suitable for such a Schottky barrier layer;

Holding on to the bottom of the line 35 platinum.

band at the Fermi level at the emission upper So that the Dynode 1 a negative Elcktroncnai: "

surface means necessarily has a sharp bend nilät, it is necessary that the lower Ran:

of the valence band and the conduction band in the and the conduction band within the semiconductor layer - ¹

with the same proximity to the emission surface. The ciek- at the point where the sharp band curvature begins:

tropositive cesium layer 5 carries electrons in the 40 is placed on an energy level that is above tlj

adjacent part of the gallium phosphide layer 4. Vacuum energy levels is. To this Bcdingunc / u

so that a thin η-conducting inversion area should meet the ionization energy /: "" the Tiei-

Emission surface exists. This inversion layer of acceptor contamination should not be greater than the difference

has a thickness Λ and ends at the point where the renz between the value of the band gap (BanJ-

Fermi level intersects the intrinsic line. 45 gap) Eq and the work function ψ. There. how nice

In the area where the Fermi level and the low level have been mentioned, the ionization energy E _{a of the} preferred acceptor level cross each other, the low levels are ionized at least equal to a value in three size acceptors. These acceptors will be with an order of 4 ΑΓ, the deep acceptors should be an energy spread of a small multiple of impurity, the semiconductor material and the electro of the factor kT ionized around the Fermi level. The 50 prositive surface layer are chosen so that . Ionization of the deep acceptors contributes to the sharp band - the following condition applies:

curvature at the emission surface.

4 kT <Ea <Eg - γ.

In the case of gallium phosphide, which contains iron as a deep acceptor, and with an iron concentration of preferably, the parameters of the dynode 1 should be about 10 ¹⁷ to ^{10 18} atoms / cm ³ , the deep acceptors will be chosen so that the distance d from the emisors typically at a distance of about 75 a sion surface at which the lower edge de: ionizes from the boundary with the cesium layer 5. Conduction band crosses the vacuum energy level

The proportion of low acceptor impurities, which is not greater than a value which is a small amount

before are ionized, decreases with the distance of times the mean free path for excited!

Emission surface, giving a varying spacing of 60 conduction band electrons within the semiconductor mate

between the low acceptor level and the Fermirials.

level. As the valence and conduction when the arrangement described is used

bands necessarily parallel to the deep acceptor- is the distance Δ from the emission surface, inner

run level, these bands are inclined obliquely, half of which the sharp band curvature occurs, small

that there is an inner potential gradient, d. H. a 65 as a value on the order of a minor!

electric drift field which, in such a direction, is a multiple of the mean free path for excited

is oriented that the electrons in the direction of the electrons, so that electrons in the conduction band mi

Emission surface are driven. residual energy above the vacuum energy level

5 w ht «; diffuse and from to the ^{elektroposit.vcn} layer 5 d 'ffu ™' ^e ™ ^unÜ _ß

of the surface 6 em.tt.crt could · ™ -Jf ™ ^l3 no additional energy ^to Bf " ^Η ^" ^^ _a "^ to enable electrons to cen PotcnUa bcrg a emission surface D e esu u. e effective Filektronenafr.nitat is therefore " ^e B ^a " ^v ·, prechen, the difference .different dem, V., kuumcner |, en level and the height of the lower conduction band above the Fermi level. how ig

shown is _T , fnk7 _P ntor contamination,

Iron, the preferred ^depth. H ^ze P \ ° _o ^r ^ ^r ^

has at R * ™ ^^^ c t vonS im of about 0.8 eV. The ^ stnisrm

on the p-type 9f ^lll T ^P ^ ^SP _R ^h 'S _st a _n d F. for about 1.3 eV while cc | Bandatat "d. ^ J-Gallium Phosphide 2 3 e \ Wj _gt . U _{| jch}

Ä ^d f ^ A as d, e difference iron-doped llalblcitcrschicht 4 made of Galliumphos nid polycrystalline _{in this embodiment}

F ■ _{Yoke could also be mono} krislallin , is on

_{the beryllium layer} 3, for example, by a vapor _{reaction of} uallium chloride (GaCl ₂ ). Ice cream

P ^ ^ _(pH} ^. _Emer _

knocked down _{about 8orc.} The N.cd. ·.-Ra ^ ^ ^^ ^^ _{to lllü}

polycrystalline gallium phosphide layer 4 the _? c- ^; _u n _{put out} has reached thickness. Under certain I "levels, the gallium phosphide layer 4 can be monocrystalline in the west, although it is grown on the crystallographically incompatible cryllium layer; 3. During the growth of the cm!

The lium phosphide layer 4 diffuses out beryllium.! ^ .P ^ ^ ^ _{distance (m to 1 (χ) A d | (} ,

Liumphosphidschicht 4 and thereby forms, ', ·.

^the ^ me

Param ^ ern. a concentration of beryl '! "j"«™" ™ ^^ " _2I ^ J

lO'Vcm »m the P .- ^ '^^ d Schiel 4, are the

a thickness of 0.5 micron door ^aie . ™ ' _d

Energy bands so sloping genc ^ j, B ^ ^ en

Area of layer 4, the m

sion e is a ^^^

there is about 0.2 volts. The J> e from fojend ^

Field: m Inner ^ r H bleite ha _Up tmass

Layer 4 has a relative "° J" _d ' _lciten .

about 6 · 10 »V / cm, for J '" e main ^{measure sc der} ^

layer 4 (i.e. the part where d.e ^ e ^ ebana ^^

essentially straight ^lini 8 ^ ^U "'J', _{Q7 charge} lent insulating and entnan off single

carrier per cm ³ . Initial example as

Although in the described execution b ^ p,

Material for the elektropositiye ^s . ^ch ' ^c «* ™ ^m J _ufde add cesium gc _{ff to the work function} ;

can also be derived from Cesiumι un ^^

sammensetzende Schich, ^{ve [applies} _jch ^e _a j _{s material} cheCaesium oxygen SchicntisianMv.

to reduce the rate of failure DeK

The dynode shown in Fig. 1 k.an _m _

be that ^{initially cns} ^ ^ j ^ _on prepared. sch.cht 3 on the substrate 2ί from A ^ _{or dje} steams. The optical transmission; The permeability of the beryl can be changed as the vapor deposition progresses, so that the vapor deposition can be terminated

Ä SÄ corresponds to the with

4 ^ n typical ^ ^ ₌

? _onc S of iron or some other deep acceptor. Impurities are desirable if they do not cause excessive crystallographic deformations in mg _hid 5, £ ht 4.

a cleaning of the exposed surface of the layer 4 becomes a thin layer 5 of Caesu. Cesium oxygen on the gallium phosphate: _{surface vapor-deposited depending on the thickness of the layer 5}

_laundri while monitoring the deposition by d ... _{of their} r Lighting nv _{Lihtthl due to go on the layer 5} -. Photoemission current b

UCr VUIl UCl Olllll ~ ui J aui Vi ι uiiu iiiiw uwx.u.- ·. · - *. ■. _c

Light rays go out '"Photoemission current b> _ is respected. The vapor deposition of the layer is b. ends when the photoemission current has a Maximo

value reached. The resulting layer thickness is deceitful. As mentioned, usually about 1 to 10 A.

If the Dynode 1 as a secondary mission canon! transmission type can be used:. < > ü the aluminum oxide substrate can be about 500 A dii. '·· " be so that on the exposed substrate surface Impinging primary electrons can penetrate up to the Galliumphos phidschicht 5. Procedure for Her self-supporting aluminum oxide layers of this type are known per se. In general, dabe

anodically oxidizes an aluminum foil until an aluminum oxide layer of the desired thickness is formed is, and then the aluminum layer ii a liquid is dissolved, so that only the Alumi The oxide layer floats on the surface of the liquid.

1 sheet of drawings

Claims (1)

1 2 11. Electron source according to claim 9, characterized Claims: characterized in that the device has primary electrons with an energy of at least 3000 eV 1. Electron source with a semiconductor body on the exposed surface of the carrier (2) made of p-type semiconductor material that delivers with a 5. Acceptor material is doped, which generates a deep-lying 12. electron source according to one of the preceding acceptor levels, and with one on one of the claims, characterized in that the surface of the semiconductor body arranged layer thickness of the semiconductor body (4) in the size to reduce the work function, characterized Order of 0.2 to 1 μπι is.
marked that on one of these first io
Surface opposite second surface of the semiconductor body (4) either a thin p-conductive Zone (21), one of which has a flat acceptor level
generating ionized acceptor impurity in contains a high concentration and is much thinner. material that is doped with an acceptor material, {las rr.it the second surface a Schottky barrier which creates a low-lying acceptance level. ~ nd with layer forms, is arranged. and that one of the one p-zone (21) arranged on a surface of the semiconductor body or of the barrier layer overlying the layer for reducing the work function.
In such a device it is expedient that trons in the conduction band of the semiconductor body are seen in front of the layer arranged on the semiconductor body. is on the order of 1 to 10 A thick and the 2. Electron source according to claim 1, characterized in that the surface of the semiconductor body has such a discharge gap that the ionization energy of the 25 imparts that the ionization energy of the acceptor material generating the deep acceptor plugs is greater than about 4A.7 ' (k Boltzrnann- materials is not greater than the difference between the constant; T absolute temperature of the semiconductor, the energy band gap and the exit energy, body) or greater than about 0.1 eV. An electron source of this kind is from the lower 3. Electron source according to claim 1 or 2. 30 rural, patent application 6 505 085 known and characterized in that the semiconductor body in the corresponding German Offenlegungsschrift: consists essentially of Ga'.üumrhos' nid and 1 564 40! has been proposed. With the well-known that the Ak electron source generating the deep acceptor level is the semiconductor body with minezeptormateria! Eiven, chrome or copper. at least two electrical connections provided by 4. Electron source according to claim 3. daüim ': i 35 which at least one is an injecting An .-- Jiluß i ^ t. in that the semiconductor body großen- from: electrons in the semiconductor body iniiordnungsniäßig lu ^'r his ΙΟ ¹ - ^"1 Liicn ^ tcmccm' corresponds to sheet, which then by the m: 'behaves the layer shy surface (emission surface) the, semiconductor body- " 5. Electron source after an animal precede * ¹ .- exit. the claims, characterized in that the to Apart from this · known electron source, the z. 13th Semiconductor body (4) essentially made of Galhum aU cathode for use in an electron tube phosphide and that the thin p-conductive line can be found, but cold electrons are also Zone (211 as acceptor cleaning, which needs the sources through which the electrons pass generated flat acceptor pegci. Zinc. Cadmium other pro / e ^ e than by injection by means of an in or contains beryllium. 45 direction of flight pre-tensioned pii-L'bergangs or the like. 6. Electron source according to claim 5, thereby generated. Examples of such electron sources are characterized by the fact that the thin p-conducting zone (21 "other an> ind / .. 13th secondary emissious dynodes. Ie ^{about K) contains 19 IkrvJliumatonie.cnv".} which the electrons as Sektmdärelektrouen through 7. Electron source after one of the preceding "- incident primary electrons of sufficient energy the claims, characterized in that the 5 "are generated, or photocathodes, called the on the first I pool (6) arranged layer (5) electrons are generated by photons. In the counter-cesium or contains cesium oxide. sentence. '. u the well-known electron source in which the H. Electron source after one of the preceding electrons with the direction of the emission surface in the claims, characterized in that the semiconductor body are injected, which have through thin, p-conductive zone (21) on a small (2) 55 primary electrons or photons generated electrons is arranged from alumina. generally no forward direction. As stated 9. Electron source according to claim S, characterized in that a \ erlii'iltiiiäiiiu "ig large Anieil then arrives characterized in that the thickness of the support (2) of the generated electrons to that of the emission surface at most 5 (Mi A is. opposite side of the thin, layered 10. Electron source according to one of the preceding; -.- ⁶ "semiconductor body, where the electrons with holes the claims, characterized in that the rekonibimeren. Through this electron pool device for generating electrons in the but the efficiency of the electron source is considerable conduction band of the semiconductor body primary elec - impaired. trons (7) with an energy necessary for the generation of the present invention is accordingly Secondary electrons in the semiconductor body (4) from ⁶ 5 are based on the task of determining the efficiency of an elec- is sufficient to improve the exposed surface of the source of water in particular by the fact that the semiconductor body arranged layer (.5) the electrons at a diffusion in the direction away from the emission surface can be prevented.