JPH02205074A - Infrared ray detector - Google Patents

Abstract

PURPOSE:To obtain an infrared ray detector having many picture elements by detecting the quantity of carriers, which are excited by the photo energy of infrared ray that enters a first composed semiconductor crystal layer, being implanted into the second crystal layer passing the band offset of a hetero junction interface between the first and second crystal layers. CONSTITUTION:A GaAs crystal layer 13 of nondope is accumulated on an Si substrate 12, and an N<+> GaAs crystal layer 14(1) is accumulated thereon, and further thereon an AlxGa1-xAs (x=0.16) crystal layer 15(2) is formed. Further thereon, an N<+> GaAs crystal layer 16 as a contact layer is formed. The number of electrons, which are injected into the AlxGa1-xAs crystal layer 15(2) passing the offset band DELTAEc of a hetero junction face 4 by the energy of infrared rays of specified wave length which are entered into the N<+> GaAs layer 14 by applying DC currents into between the contact layer 16 of a detector 11 and the N<+> GaAs layer 14(1), is detected as the fluctuation of currents which flow between the contact layer 16 and the N<+> GaAs layer 14, and is detected as the fluctuation of electric waves, which are implanted into the input diode of the charge transfer device, with a charge transfer device.

Description

[Detailed Description of the Invention] [Summary] Regarding an infrared detection device, the object is a detection device having a large number of pixels (and is sensitive to infrared rays in the 8 to 12 μm band), a first compound semiconductor crystal layer, a first compound semiconductor crystal layer, and a second compound semiconductor crystal layer. A heterojunction is formed between the first compound semiconductor crystal layer and a second compound semiconductor crystal layer having a different energy band gap, and the first compound is excited by infrared light energy incident on the first compound semiconductor crystal layer. The amount of carriers in the semiconductor crystal layer injected into the second compound semiconductor crystal layer beyond the band offset of the heterojunction interface between the first and second crystal layers is detected.

[Industrial application field]

The present invention relates to an infrared detection device, and particularly to a detection device that is sensitive to infrared rays in the 8 to 12 μm band and has a large number of pixels.

Charge transfer devices, etc. that form an infrared detection device using compound semiconductor crystals such as mercury, cadmium, and tellurium that are highly sensitive to infrared rays and have narrow energy band gaps, and process the signals obtained by this detection device. Silicon (S
Infrared imaging devices are well known in which the input diodes of these charge transfer devices and detection devices are connected using metal bumps such as indium.

Among such infrared imaging devices, there has recently been a demand for high-performance infrared imaging devices with a large number of pixels, about 500×500 pixels, on the same level as imaging devices such as televisions.

[Conventional technology]

Conventionally, infrared detection devices used in such infrared imaging devices have been made of mercury, cadmium, tellurium (Hg1~X
CdX Te) and indium antimony (In
5b), etc., but it is difficult to obtain high-quality crystals with a large main area, and the number of pixels is limited to about 128 x 12B pixels. , 500. , about 500 pixels.

It is difficult to obtain a large number of detection devices.

Therefore, St and, for example, platinum (Pt), lead is palladium (
A Schottky junction is formed using a metal such as Pd), and a detection device is formed using a Schottky junction diode, which is combined with a signal processing device to obtain an infrared imaging device with 512 x 512 pixels.

[Problem to be solved by the invention]

However, the above-mentioned Schottky junction type infrared detection device has a sensitivity wavelength of 5 μm or less, and it is not possible to obtain a high-performance detection device that is sensitive to infrared rays in the 8 to 12 μm band, which is necessary to detect objects at a long distance. The current situation is that this is not the case.

Therefore, in place of such a detection device using a Schottky junction diode, there is a demand for a detection device that is sensitive to infrared rays in the 8 to 12 μm band and has a large number of pixels.

The present invention was made in view of the above-mentioned matters, and uses compound semiconductor crystals of the ■-■ group, from which crystals with a large area are easily obtained, and
The object of the present invention is to obtain an infrared detection device that is sensitive to infrared rays in the 0 μm band and has a large number of pixels.

[Means to solve the problem]

As shown in the principle diagram of FIG. 1, the infrared detecting device of the present invention that achieves the above object has a first compound semiconductor crystal layer 1 and a second compound semiconductor crystal layer 1 which have different energy band gaps. A heterojunction is formed with the second compound semiconductor crystal layer 2, and the carriers 3 in the first compound semiconductor crystal layer l excited by the infrared light energy incident on the first compound semiconductor crystal layer 1 are , the amount of the second compound□semiconductor□crystalline layer 2 is detected beyond the band offset 5 of the heterojunction interface 4 between the first and second crystalline layers 1.2. .

[For production]

As shown in the principle diagram of Fig. 1, the first layer of N-type GaAs doped with impurities at a high concentration of 1020 atoms/C113 or more.
The Fermi level EF of the compound semiconductor crystal layer 1 is higher than the energy level of the bottom of the conduction band Eel. Therefore, the free electrons 3 in the crystal are in a heterojunction with the crystal layer 1,
And the energy band gap is larger than that of the crystal layer 1, and the band offset ΔEC formed at the heterojunction surface 4
Aluminum, gallium, arsenic (Af, Ga
+--As) is implanted into the crystal layer 2 side.

Here, the band offset ΔEc is the difference between the energy level of the conduction band Ecl of the first compound semiconductor crystal layer l and the bottom energy level Ecl of the conduction band of the second compound semiconductor crystal layer 2, and ΔEC=Ec.

It is expressed as Ecz.

This band offset depends directly on 812XGa+-xX of As.

In addition, the number of free electrons excited by the energy of incident infrared rays varies depending on the magnitude of the energy corresponding to the wavelength of the incident infrared rays, so for example, the number of free electrons excited by infrared rays with energy of a wavelength of 10 μm is detected. For this reason, the value of the band offset ΔEc must be set to 0.12 eV, and therefore the X value must be set to a value of 0.16.

Furthermore, in order to detect a wavelength of 5 μm, it is necessary to set the x value to a value of 0.33, so the AI! , xGap-11As, infrared rays having wavelengths in the 8 to 12 μm band can be detected.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a configuration diagram showing one embodiment of the infrared detection device of the present invention, and FIG. 3 is a sectional view of one embodiment of the device of the present invention.

As shown in FIGS. 2 and 3, the infrared detection device 11 of the present invention has a non-doped GaA film on an St substrate 12.
An s-crystal layer 13 is laminated, and on top of that is an N' crystal layer doped with N-type impurities at a high concentration of about 1020 atoms/cm3.
"A GaAs crystal layer 14 (1) is laminated, and on top of that a ^1XGa+-x As (x=0.16) crystal layer 15
(2) are both formed using a molecular beam epitaxial growth method or the like. Furthermore, N is added as a contact layer on top of that.
``A GaAs crystal layer 16 is formed.
"Aj2x Ga+-x from the surface of the GaAs crystal layer 16
Mesa etching is performed up to the As crystal layer 15 to define pixels.

Further, as a charge transfer device signal processing device 17 that processes the signal obtained by the detection device 11, a P-type Si substrate 21 is used.
An input diode 22 is formed by introducing an N-type impurity into the substrate 21 , and an input gate electrode 24 and an input gate electrode 24 are formed on the substrate 21 to accumulate the signal injected into the input diode 22 through an insulating film 23 under the transfer electrode 25 . , a transfer electrode 2 that transfers the signal
5 and the like are formed by vapor deposition of poly-Si or aluminum. These input diodes 22 and the contact electrode 16 of the detection device described above are connected via a coupling electrode 26 made of gold or the like.

As in this embodiment, a GaAs crystal layer 1 is placed on an St substrate 12.
By forming the detection device 11 after forming the Si
When the charge transfer device 17 and the detection device 11 formed on the substrate 21 are bonded together using a bonding electrode made of gold or the like, the problem of distortion occurring due to the difference in coefficient of thermal expansion between the substrates can be solved. In addition, since a large-area, high-quality GaAs crystal can be obtained, the
This enables an infrared imaging device with a large number of pixels, about 0.times.500 pixels.

In addition, crystals such as St and GaAs can withstand temperatures up to 500°C, and their mechanical strength is
The St substrate 21'r: The formed charge transfer device 17
When bonding the GaAs-A I GaAs heterojunction infrared sensing device 11, In metal bump bonding is unnecessary, and the bonding electrode 26 is a gold electrode with a thickness of 2 to 3 μm.
The sensing device 11 and the charge transfer device 17 can be combined.

Therefore, it is also possible to form this gold electrode by vapor deposition, which simplifies the process of manufacturing the imaging device and eliminates the problem of misalignment between the infrared detection device and the charge transfer device when they are combined.

In this example, in order to detect infrared rays whose cutoff wavelength is 10 μm, a band offset ΔEc=120 meV is required, and in this case, Δ1
．． It is necessary to set x of XGa+-x As = 0.16, but in order to detect infrared rays with a cutoff wavelength of 5 μm, the value of band offset ΔE e = 240 meV and 1
〇-, then x of Aj2x Gap-xAs = 0.
It needs to be 32.

In order to detect infrared rays using the detection device of the present invention, as shown in FIGS. 2 and 3, the detection device 1
Infrared rays are incident from the back side of 1 as shown by arrow A.

Then, the contact layer 16 of the detection bag W11 and the N″GaAs
Layer 14 (DC voltage is applied between laminar flow 4, N″Ga'A
The number of electrons injected into the Affix Gap-xAs crystal layer 15 (2) beyond the offset band ΔEc of the heterojunction surface 4 due to the energy of infrared rays of a predetermined wavelength incident on the s-layer 14 is calculated as follows: ″GaA
The amount of incident infrared rays and its wavelength are detected by detecting the current as a variation in the laminar current flowing through the S layer 14, and detecting this changed current as a variation in the current injected into the input diode of the charge transfer device by the charge transfer device. can be detected.

In FIG. 2, Ev+ is the upper energy level of the valence band of the N'' GaAs crystal layer 14, and Ec2 is A
I! ,
is the energy level at the bottom of the conduction band of the contact layer 16,
EV3 indicates the upper energy level of the valence band of the contact layer 16.

By doing so, an infrared imaging device having a large number of pixels and having sensitivity to infrared rays having a wavelength in the 8 to 12 μm band can be easily obtained.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to obtain a high-quality, large-area GaAs crystal for forming a heterojunction detection device on an St-based substrate, which is easy to obtain a high-quality crystal. can get. In addition, free carriers (electrons) excited with energy corresponding to the wavelength of the incident infrared rays are detected using the band offset caused by the difference in energy band gap due to the heterojunction.
An imaging device sensitive to wavelengths in the 8-12 μm band can be easily obtained.

=11

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of the infrared detection device of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the infrared detection device of the present invention, and Fig. 3 is an illustration of an imaging device using the infrared detection device of the present invention. It is a sectional view showing an example. In the figure, 1 is a first compound semiconductor crystal layer, 2 is a second compound semiconductor crystal layer, 3 is a free electron, 4 is a heterojunction surface, 5 is a band offset, 11 is an infrared detector, 12.21 is S
t substrate, 13 is a GaAs crystal layer, 14 is N′″GaAs
A crystal layer, 15 is an Af, .Ga, -, As crystal layer, 16 is an N''GaAs crystal layer (contact layer), 17 is a charge transfer device, 22 is a human diode, 23 is an insulating film, and 24 is an input gate electrode. , 25 indicates a transfer electrode, and 26 indicates a coupling electrode.
Figure 1 Δ Agent Patent Attorney Sada Igata - M-Kukei Group L Rinpa Burning Fir - Rumors of Maru Exemplar Peda Figure 2

Claims (3)

[Claims] (1) forming a heterojunction with a first compound semiconductor crystal layer (1) and a second compound semiconductor crystal layer (2) having a different energy band gap from the first compound semiconductor crystal layer; The first compound semiconductor crystal layer (1) is excited by infrared light energy incident on the compound semiconductor crystal layer (1).
1) detecting the amount of carriers injected into the second compound semiconductor crystal layer (2) beyond the band offset (5) of the heterojunction interface (4) between the first and second crystal layers; An infrared detection device characterized by: (2) Impurities are introduced at a high concentration so that the energy level of the first compound semiconductor crystal layer (1) to which the infrared rays are incident is degenerated, and the second compound semiconductor crystal layer (2)
is formed by controlling the composition so that it has a band offset (5) that allows carriers excited by infrared energy of a predetermined wavelength to be injected at the heterojunction interface (4) between the crystal layers. The infrared detection device according to claim 1, characterized in that: (3) A gallium arsenide crystal layer (14) in which the first compound semiconductor crystal layer (1) and the second compound semiconductor crystal layer (2) are laminated on a silicon substrate (12) and an aluminum gallium arsenide crystal layer (14). Arsenic (Al_xGa_1_-_xAs
) crystal layer (15), the Al_xGa_1_-
The infrared detection device according to claim 1 or 2, wherein the x value of _xAs is 0.1 to 0.4.