JP2002100752A - Light-receiving array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a light-receiving array by arraying multiple light-receiving sensors for which a base layer functioning as an energy filter is provided between a light-absorbing layer and a collector layer. SOLUTION: The light-receiving array is provided which comprises a substrate and a plurality of light-receiving sensors formed in common on the substrate. Each light-receiving sensor comprises an emitter layer, a base layer, and a collector layer, and a light-absorbing region is provided between the emitter layer and the base layer, with the base layers of a plurality of light- receiving sensors being connected in common by a ground pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an optical semiconductor device, and more particularly to an infrared light receiving array for receiving far-infrared light in a band of 8 to 12 μm. Such an infrared light receiving array is useful for highly accurate detection of night vision devices and heat sources in the civil and military fields.

[0002]

2. Description of the Related Art A multi-quantum well infrared light receiving sensor for detecting far-infrared light in a band of 8 to 12 μm by photo-induced intersubband transition of carriers in an AlGaAs / GaAs multi-quantum well has been conventionally known ( Levine, BF, J.
Appl. Phys. 74, 1993, R1-R80).

FIG. 1 shows the configuration of such a conventional multiple quantum well infrared light receiving sensor 10.

Referring to FIG. 1, the multi-quantum well infrared light receiving sensor 10 is formed on an n-type GaAs substrate 11 constituting an emitter layer, and an AlGaAs / GaAs multi-quantum A well structure 12 and a p-type AlGaAs formed on the multiple quantum well structure 12
and a n-type GaAs collector layer formed on the base layer 13 and diffracts a far-infrared light beam incident on the collector layer 14 through the substrate 11. A diffraction grating 14A is formed.

[0005] As shown in FIG.
2 is a barrier layer 12A made of undoped AlGaAs;
It has a configuration in which quantum well layers 12B made of GaAs doped with n-type by Si are alternately stacked, and electrons in the quantum well layers 12B are excited by an incident far-infrared light beam, so that a photocurrent flows. . FIG. 2 shows the band structure of the multiple quantum well infrared light receiving sensor 10 of FIG.
It is a figure shown about c.

Referring to FIG. 2, the base layer 13 forms a potential barrier between the multiple quantum well structure 12 and the collector layer 14, and the incident far infrared light beam is formed in the quantum well layer 12B. Are excited as hot electrons by the base layer 13.
Over the potential barrier of the collector layer 14
To reach. In contrast, electrons excited by lattice energy, that is, phonons, in the quantum well 12B cannot cross the potential barrier formed by the base layer 13 and do not reach the collector layer 14.

As described above, the base layer 13 functions as an energy filter for the electrons reaching the collector layer 14 and contributes to reducing the dark current of the multiple quantum well infrared light receiving sensor 10.

[0008]

By the way, if an attempt is made to construct an image sensor for acquiring an image in the far-infrared light band using such a multiple quantum well infrared light-receiving sensor 10, the light-receiving sensor 10 will be used as an image sensor. It is necessary to arrange a large number on the focal plane of the optical system of the sensor to form an array.

At this time, the base layer 13 constituting such an energy filter of the excited electrons must be connected to each other in the respective elements constituting the array, and the electrons blocked by the potential barrier must escape to the ground. However, this requires a complicated wiring pattern extending over the light receiving surface of the array. Such a wiring pattern must be formed so as not to reduce the effective area of the light receiving surface.

Accordingly, it is a general object of the present invention to provide an infrared light receiving array which has solved the above-mentioned problems.

A more specific object of the present invention is to provide a light receiving array in which a large number of light receiving sensors are arranged, in which the base layers of the respective light receiving sensors in the array are commonly connected without reducing the light receiving area of the array. An object of the present invention is to provide a light receiving array having a wiring structure.

[0012]

The present invention solves the above problems,
In a light receiving array including a substrate and a plurality of light receiving sensors commonly formed on the substrate, each light receiving sensor includes an emitter layer, a base layer, and a collector layer, and is disposed between the emitter layer and the base layer. Is provided with a light absorption region, and the light receiving array is characterized in that the base layers of the plurality of light receiving sensors are commonly connected by a ground pattern.

In each of the light receiving sensors, the base layer and the light absorbing region are separated from the base layer and the light absorbing region of the adjacent light receiving sensor by an element isolation groove. Are connected in common by a conductor pattern formed on an insulating film that fills in. Although the collector layer is patterned to expose the base layer surface along the element isolation groove,
The conductor pattern is formed so as to cover an exposed surface of the base layer. Further, the collector layer may be patterned so as to expose the surface of the base layer at four corners of the light receiving sensor region defined by the element isolation groove. In this case, the conductor pattern may be formed of the base layer. Is formed so as to cover the exposed surface of the.

According to the present invention, since the ground pattern for commonly connecting the base layers can be formed along the element isolation grooves, the light receiving area of the light receiving array is not sacrificed by the common connection wiring of the base layer. Such a ground pattern is simple and easy to form. Such a ground pattern can be easily formed by depositing a conductor layer. However, when the conductor layer is formed in this way, the ground pattern is formed in one plane corresponding to the surface of the base layer, and is complicated. There is no need to extend the structure or provide a multilayer wiring structure.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG.
2B are a plan view and a cross-sectional view showing the configuration of the multiple quantum well light receiving array 20 according to the first embodiment of the present invention. However, in FIGS. 3A and 3B, the same reference numerals are given to the parts described above, and the description will be omitted.

Referring to FIG. 3A, the multiple quantum well light receiving array 20 has a large number of light receiving elements separated from each other by element isolation grooves 11A on a common n-type GaAs substrate 11 constituting an emitter layer. As shown in the cross-sectional view of FIG. 3B, each light receiving element has the same configuration as the multiple quantum well infrared light receiving sensor 10 described above with reference to FIG.

As shown in FIG. 3B, the device isolation groove 1 is formed.
1A is filled with an insulating film such as polyimide, and the collector layer 14 is patterned so as to continuously expose the surface of the base layer 13 along the element isolation groove 11A. Further, in the multiple quantum well light receiving array 20 according to the present embodiment, as shown in FIG. 3B, the exposed surface of the base layer 13 is covered with the conductor layer 15 forming the base electrode 15A.

As can be seen from the plan view of FIG. 3A, the base electrodes 15A are connected to each other by bridging portions 15B formed on the element isolation grooves 11A in the conductor layer 15. Then, by grounding the base terminal B of FIG. 3B, the conductor layer 15 is grounded, and the array 2
The base layer 13 is commonly grounded in all of the light receiving elements in the zero. As a result, the phonon-excited electrons blocked by the base layer 13 acting as an energy filter in the band structure diagram of FIG. 2 are quickly released to the ground.

As shown in FIG. 3B, in the multiple quantum well light receiving array 20, each light receiving element is an emitter layer 11.
Are connected to a common emitter terminal E, while each collector layer 14 is connected to a corresponding collector terminal C. As a result, the output signal of each light receiving element is connected to the corresponding collector terminal C. Obtained on terminal C. [Second Embodiment] FIG. 4 is a plan view showing the structure of a multiple quantum well light receiving array 30 according to a second embodiment of the present invention. However, in FIG. 4, the parts described above are denoted by the same reference numerals, and description thereof will be omitted.

Referring to FIG. 4, in this embodiment, similarly to the previous embodiment, the light-receiving elements constituting the light-receiving array 30 are separated from each other by an element isolation groove 11A on an n-type GaAs substrate 11 constituting an emitter layer. The element isolation groove 11A is filled with an insulating film such as polyimide. In this embodiment, the collector layer 14 is patterned only at four corners of each light receiving element. The base layer 13 is exposed only at these four corners in each light receiving element. Along with this, by forming a metal contact layer on such exposed four corners,
A bridge portion 25B corresponding to the bridge portion 15B described above with reference to FIG. 3A is formed.

In this embodiment, the base layer 13 is not exposed except for the bridging portion 25B, so that the area of the collector layer 14 is larger than that of the previous embodiment. Accordingly, in the present embodiment, it is possible to increase the detection sensitivity of the photocurrent.

[Third Embodiment] Next, the manufacturing process of the multi-quantum well light-receiving array of the present invention will be described with reference to FIGS.

Referring to FIG. 5A, an emitter contact layer (not shown) is formed on an n-type GaAs substrate 11, and an In contact is formed so as to cover the emitter contact layer.
The GaAs etching stopper layer ES1 is formed. A multiple quantum well structure 12 having a superlattice structure is formed by alternately laminating an AlGaAs layer and a GaAs layer thereon, and a p-type GaAs base layer 13 is formed on the multiple quantum well layer 12. You.

The base layer 13 is covered with a second InGaAs etching stopper layer ES2, and an n-type Ga
An As collector layer 14 is formed, and this further forms a third I
It is covered by the nGaAs etching stopper layer ES3.

GaAs is formed on the InGaAs layer ES3.
5A, the GaAs layer is patterned by using the InGaAs layer ES3 as an etching stopper, thereby forming the diffraction grating 14A.
Is formed.

Next, in the step of FIG.
The aAs layer ES3 is patterned by a resist process except for a region where the diffraction grating 14A is formed corresponding to each of the light receiving elements.
Of 4, the portion 11B located between one light receiving element and the light receiving element adjacent thereto is exposed.

Next, in the step of FIG. 5C, the exposed region of the collector layer 14 is removed by the etching stopper film ES2.
The collector layer 14 is patterned corresponding to each light receiving element by dry etching until the light is exposed. As a result of such patterning, the region 11
An element isolation groove for isolating the collector layer 14 is formed corresponding to B.

Further, in the step of FIG. 5D, the etching stopper film ES2 is patterned by a resist process, and the base layer 13 corresponds to the region where the element isolation groove 11A is to be formed as described with reference to FIG. Exposed.

Next, in the step of FIG. 5E, the base layer 13 and the multiple quantum well structure 12 thereunder are patterned until the etching stopper film ES1 is exposed, so that the light receiving element is formed in the element isolation groove 11A. Are formed on the substrate 11 while being separated from each other.

Further, in the step of FIG. 5F, the element isolation groove 11A is filled with a polyimide layer.
After the unnecessary polyimide layer is removed in the step (G), the conductive layer 15 is formed on the polyimide layer so as to connect the base layers of the adjacent light receiving elements to each other.
In the step of FIG. 5G, a conductor pattern 16 constituting a collector electrode is also formed on the collector layer 14 of each light receiving element, corresponding to the collector terminal C.

As described above, in this embodiment, since the conductor pattern 15 is mainly formed on the element isolation groove 11A, there is no need to provide a complicated wiring for interconnecting the base layers 13. In each light receiving element, the area of the collector layer 14 is not sacrificed for wiring. Particularly, in the light receiving array 30 according to the embodiment of FIG.
By using the cross-linked conductor pattern 25B in place of the collector layer 14, the collector layer 14 for forming the cross-linked pattern is formed.
Is reduced to a minimum. FIG.
According to the step (G), the number of steps does not increase when such a crosslinked pattern is formed.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to such specific embodiments, and various modifications and alterations are possible within the scope of the appended claims. is there.

(Supplementary Note 1) In a light receiving array including a substrate and a plurality of light receiving sensors commonly formed on the substrate, each light receiving sensor includes an emitter layer, a base layer, and a collector layer. A light-absorbing region is provided between the light-receiving element and the base layer, and the base layers of the plurality of light-receiving sensors are commonly connected by a ground pattern. (1) (Supplementary note 2) In each of the light receiving sensors, the base layer and the light absorbing region are separated from the base layer and the light absorbing region of an adjacent light receiving sensor by an element isolation groove, and the plurality of light receiving sensors are provided. 3. The light-receiving array according to claim 1, wherein the base layer is commonly connected by a conductor pattern formed on an insulating film filling the element isolation groove, and the conductor pattern forms the ground pattern. . (2) (Supplementary Note 3) In each of the light receiving sensors, the collector layer is patterned so as to expose the surface of the base layer along the element isolation groove, and the conductor pattern is formed on an exposed surface of the base layer. 3. The light receiving array according to claim 2, wherein the light receiving array is formed so as to cover the light receiving element. (3) (Appendix 4) In each of the light receiving sensors, the collector layer is patterned so as to expose the surface of the base layer at four corners of a light receiving sensor region defined by the element isolation groove, and the conductor patterning is performed. 3. The light receiving array according to claim 2, wherein the light receiving array is formed so as to cover an exposed surface of the base layer. (4) (Supplementary note 5) Among the supplementary notes 1 to 5, wherein the light absorption region has a multiple quantum well structure in which an n-type doped quantum well layer and an undoped barrier layer are alternately repeated. A light receiving array according to any one of the preceding claims.

(Supplementary Note 6) The light receiving device according to any one of claims 1 to 5, wherein the base layer forms a potential barrier having a height such that electrons excited by phonon are blocked. array.

(Supplementary Note 7) The conductive pattern is formed substantially on the same plane.
5. The light receiving array according to any one of the items 4. (5)

According to the present invention, when a large number of light receiving elements including a base layer forming a potential barrier acting as an energy filter are arranged to form a light receiving array having sensitivity in the far-infrared band, a simple structure can be obtained. By the conductive pattern
The base layer can be commonly grounded without reducing the effective light receiving area, and phonon excited electrons that cause dark current can be blocked by the base layer and quickly escaped to ground. become.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a conventional infrared light receiving sensor.

FIG. 2 is a band structure diagram of the light receiving sensor of FIG. 1;

FIGS. 3A and 3B are diagrams showing a configuration of a light receiving array according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a light receiving array according to a second embodiment of the present invention.

FIGS. 5A to 5G are diagrams showing a manufacturing process of a light receiving array according to a third embodiment of the present invention.

[Description of Signs] 10 Infrared light receiving sensor 11 Substrate (emitter) 11A, 11B Isolation groove 11C Polyimide 12 Multiple quantum well light absorption layer 13 Base layer 14 Collector layer 14A Diffraction grating 15 Conductor pattern 15A Base electrode 15B, 25B Bridge portion 16 Collector electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G065 AB02 BA06 BA14 BA34 BB28 BE08 DA18 4M118 AA01 BA09 CA01 CA09 CB02 EA16 EA20 FB09 FB22 GA10 5F049 MA13 MB07 NA05 NB05 NB07 PA14 PA17 QA16 RA02 SE05 SS04 SZ08 WA01

Claims (5)

[Claims] 1. A light-receiving array comprising a substrate and a plurality of light-receiving sensors commonly formed on the substrate, wherein each light-receiving sensor comprises an emitter layer, a base layer, and a collector layer; A light-receiving array, wherein a light-absorbing region is provided between the light-receiving layers and the base layers of the plurality of light-receiving sensors are commonly connected by a ground pattern. 2. In each of the light receiving sensors, the base layer and the light absorbing region are separated from a base layer and a light absorbing region of an adjacent light receiving sensor by an element isolation groove. The base layer is
2. The light receiving array according to claim 1, wherein the light receiving array is commonly connected by a conductor pattern formed on an insulating film filling the element isolation groove, and the conductor pattern forms the ground pattern. 3. 3. In each of the light receiving sensors, the collector layer is patterned so as to expose the surface of the base layer along the element isolation groove, and the conductor pattern covers an exposed surface of the base layer. The light receiving array according to claim 2, wherein the light receiving array is formed as described above. 4. In each of the light receiving sensors, the collector layer is patterned so as to expose the surface of the base layer at four corners of the light receiving sensor region defined by the element isolation groove, and the conductor patterning is performed. 3. The light receiving array according to claim 2, wherein the light receiving array is formed so as to cover an exposed surface of the base layer. 5. The method according to claim 2, wherein the conductive patterns are formed on substantially the same plane.
A light receiving array according to any one of the preceding claims.