DE3321535A1 - Method for producing a semiconductor photocathode - Google Patents

Abstract

A method is proposed for producing a III-V semiconductor photocathode, in the case of which method a semiconductor-glass bond is produced in an oxygen-free atmosphere.

Description

3.

Licentia Patent-Verwaltungs-GmbH PTL-UL / Ara / eng

Theodor-Stern-Kai 1 UL 83/57

6000 Frankfurt (Main) 70

description

Method of making a
Semiconductor photocathode

The present invention relates to a method for producing a semiconductor-glass composite, in particular for III-V connections photocathodes, in which a semiconductor body is firmly connected to a glass substrate over a large area using pressure and elevated temperature.

Thin III-V connectors are suitable as infrared-sensitive photocathodes for night vision. Since the thin semiconductor is not mechanically stable alone, it is used initially in a mechanically stable thickness of about 250μιη and then at an elevated temperature of about 400 "C to 700 ⁰ C under pressure or electrostatically with a thicker stable, transparent support of Glass or sapphire as an entrance window for the IR light connected by the following chemical (US-PS 39 59 045) or

UL »3/57

Cliemomechanical thinning (DE-OS 29 09 985) is the HaIblüitcrkürpur so white gcd ü η η t (ζ. U. aul ^: 1 to 3 μm) that the electrons generated by the light in the semiconductor on the side facing away from the carrier Semiconductor can leak. The optical image is thus converted into an electronic LzL.

A thin amorphous penetration layer is expediently used to connect semiconductor and glass. Anglavermittler who previously on the semiconductor body applied pyrolytically or by sputtering. To the optical adjustment of the refractive indices of semiconductors and Glass carrier, d. H. to reduce reflection losses When light is shone through, the Anglasvermittler can consist of several amorphous layers and so on at the same time fulfill the function of an anti-reflective covering.

With conventional anglas processes, the mechanical Manipulations, such as B. local exertion of pressure or and taking off a weight, carried out in an open system carried out by protective gas. that both the interface between semiconductor and glass or Anglaevermittler and the Anglaevermittler changes drastically even during simulated anglas processes changes. There are metallic and oxidic intermediate layers ten (As, Ga ^ O-), such as B. given in the following Table 1 for the example of a GaAs half-liner. Also, the Anglais broker layer becomes in volume and on the connection interface with the glass body with Ga enriched.

. 5.

Ul, 83/57

Tab. L

SiO ₂ Layers olge 5% Ga, Ga ₂ O ₃ before the tempering 5% As ₂ O ₃ Ga ₁ Ga ₂ O ₃ 1 <3 onm GaAs SiO ₂ with approx. Ga ₂ Oo with approx. As 250μπ> GaAs after <lOnm 130nm ** 20nm * V10nm 250mm

The present invention is based on the object of the formation of intermediate layers, in particular of the aforementioned Art, in the connection area between glass and semiconductor to prevent.

According to the invention, this object is achieved in that the connection process in a reaction chamber to the greatest possible extent Oxygen-free, especially when there is an oxygen content is made of less than 100 ppm.

When using the method described, no undesired intermediate layers occur. The process prevents even with oxygen-permeable fishing brokers or '. Anti-reflective coatings cause oxidic attack and decay of the semiconductor interface. A significantly higher tremineion can be achieved, · ηί «ρν» οη · η <1 an increase in the electron yield in the semiconductor of approx. 60% compared to that in the conventional process.

UL 83/5

The importance of this method can also be seen from calculations based on a theory for determining the transmission and reflection of any sequence of thin layers with the refractive index * n and the absorption index k. The following Table 2 are for two wavelengths in the near to IK area, the percentage reach the incident light in the infrared-sensitive semiconductor (transmittance) can be reacted and thus here in an electromagnetic African image. According to the conventional method, the intermediate layers, in particular the metallic As layer, absorb approx. 50% of the incident light. With the new process, the transmission can be increased to 81%, as shown in Table 2 for the example of angled SiO. With a multi-layer anti-reflective coating (e.g. made of SiO »and TiO ₂ ), almost 100% can then be achieved.

Tab. 2

Transmission after Anglasen for

870nm

670nm

with intermediate layers

53%

48%

according to the invention without intermediate layers

81%

81%

On the basis of the exemplary embodiment shown in FIGS. 1 and 2, the invention will be explained in more detail below explained.

The FIG. 1 shows a semiconductor body 1 which can consist of a plurality of semiconductor layers. He is occupied with a thin amorphous base of St, possibly also consisting of various amorphous materials as an angled mediator and / or as an anti-reflective coating. The transparent carrier is either a uniform type of Giass, such as Corning glass 7056 or Schott glass ZKN7 or a hard one

UT, 83/57

Carrier glass or sapphire with a soft solder glass. The surface 20 1 of the layer 2 and 301 of the carrier 3 are connected to one another under pressure at an elevated temperature. This Connectivity ^ young process according to the invention in acidic α tofffreier environment preferably in a vertical system, as shown in FIG. 2 shown. The wall of the reaction space consists of a quartz or metal tube. A pump device or a protective gas bottle can optionally be connected to the inlet connection 5. The output 6 contains, for example, a check valve. On part of its length , the tube 4 is lifted approximately with a spiral 7. In the upper part there is a cooling device 8 for the mostly insufficiently temperature-resistant vacuum seal 9 and for the bellows 11 embedded in the upper cover 10. The latter enables mechanical manipulations in the device, for example with the rod 12.

The semiconductor wafer 1, covered with the amorphous layer 2, is inserted into a jig 13 together with the glass carrier 3. After closing the system is evacuated and / or thoroughly purge gas durchgeachickt to any Sauer 8tof te f res to remove. This is followed by slow heating to the glass temperature. Here, with constant gas throughput, either the rod 12 is placed locally on the glass carrier 3 or an even hoof is placed in order to realize the bond. After the device has cooled down and the composite structure has been removed, it is processed further to form a semiconductor photocathode.

In a preferred exemplary embodiment, the semiconductor 1 consisted of GaAs with a thickness of approximately 25 μm _1, the Anglasvermittler 2 consisted of pyrolytically applied SiO ₂ with a thickness of approximately 130 nm. The glass carrier 3 consisted of Schott glass ZKN 7.

g - UL 83/57

K η became an ob on es Gewi, el ι I: from 500g au Fßo I ep, I: to the setting the necessary on-glass printing. The oven 4 off

-3 Quartz was flushed through after a short evacuation phase at 10 Torr with hydrogen purified in a palladium cell. The furnace was heated up to 670 ^° C., this temperature was maintained for about 1 hour and then cooled in about 1 hour. During this time, the semiconductor-glass composite was created without undesired intermediate layers and without undesired changes in the composition of the Anglasvermittiers. This semiconductor-glass composite resulted in a semiconductor photocathode with excellent transmission properties. These improved properties are essentially attributed to the fact that attention was paid to the utmost freedom from oxygen when connecting the semiconductor to the glass substrate.

Lebrseite -

Claims (10)

Licentia Patent-Verwaltungs-GmbH PTL-UL / Am / deu Theodor-Stern-Kai 1 UL 83/57 6000 Frankfurt (Main) 70 Claims Method for producing a semiconductor-glass composite, in particular designed as a photocathode, in which
a semiconductor body is firmly connected to a glass substrate over a large area using pressure and elevated temperature, characterized in that the connection process in a reaction chamber in a higher atmosphere
Oxygen-free, in particular with an oxygen content of less than 100 ppm. 2. The method according to claim 1, characterized in that the joining process in a vacuum of less than -3 -4 10, in particular 10 Torr, is made. 3. The method according to claim 1, characterized in that the connection process in the purest purging gas atmosphere,
especially in a hydrogen, argon or nitrogen substance atmosphere, is made. Ul, H3 / 57 4. The method according to any one of claims 1 to 3, characterized characterized in that the reaction space can be heated from the outside and with a vacuum-tight device for performing mechanical manipulations on the semiconductor glass body ) 5 provided 1st. 5. The method according to any one of claims 1 to 4, characterized in that a III-V compound semiconductors with is connected to the glass carrier. 6. The method according to claim 5, characterized in that LO is a binary, ternary or qu * ternary containing gallium III-V connection semiconductors connected to the glass carrier will. 7. The method according to any one of claims 1 to 6, characterized characterized in that the semiconductor body prior to the connection L5 dung process on its interface with at least a thin, oxygen-permeable angled glass mediator layer. 8. The method according to claim 7, characterized in that the semiconductor body with one or more amorphous • 0 Anglas mediator layers, in particular metal or Semi-metal oxides or nitrides, is coated. 9. Method according to one of Claims 7 to 8, characterized characterized in that the Anglas mediator layers through thermal decomposition (pyrolytic) or by puttering be applied to the semiconductor body. 10. The method according to any one of claims 1 to 9 »dad, ur.ch characterized in that during the connection process in the reaction space an oxygen content of less than 50 ppm, preferably less than 25 ppm, in particular less than 10 ppm, prevails.