JP2003273392A - GaN SYSTEM SEMICONDUCTOR PHOTO ACCEPTANCE DEVICE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Schottky barrier type GaN system photo acceptance device detecting light of which wavelength is longer than that of light of 365 nm. <P>SOLUTION: An i layer 1 comprising In<SB>x</SB>Ga<SB>y</SB>Al<SB>z</SB>N whose band gap is smaller than GaN is used as a photo acceptance layer, and a top surface of the i layer is provided with a Schottky electrode P1 to make it the Schottky barrier type photo acceptance device. It's preferable that a surface layer is interposed so as to improve Schottky contact against the i layer. In the surface layer, GaN system semiconductor whose band gap is larger than the i layer is used on at least Schottky contact portion. Thus, good Schottky contact is secured. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Schottky barrier type GaN-based semiconductor light receiving element, and more particularly to an element sensitive to light having a wavelength longer than 365 nm.

[0002]

2. Description of the Related Art There are many GaN-based semiconductor light-receiving elements using a GaN-based semiconductor crystal (hereinafter, also referred to as GaN-based crystal) as a light-receiving layer, which are based on many light-receiving principles, and one of them is a Schottky. There is a barrier type light receiving element.

A conventional general structure of a Schottky barrier type light receiving element is, as shown in FIG. 7, a sapphire substrate 10.
0 through the GaN-based low temperature growth buffer layer 101,
n-type GaN crystal layer (Si-doped high carrier concentration layer) 10
2. An i-layer (light-receiving layer) 103 made of GaN crystal is sequentially formed, and the i-layer 103 is formed by RIE (Reactive Ion Etchin).
g) to partially remove the n-type GaN crystal layer 102
Are exposed, and a Schottky electrode P10 is formed on the upper surface of the i layer 102, and an ohmic electrode P20 is formed on the exposed surface of the n-type GaN crystal layer 102.

The incident direction of the light to be received may be from the side of the substrate. However, by adopting a comb-shaped electrode or a transparent electrode as the form of the Schottky electrode to be incident, the light can be transmitted through the gap between the electrodes. It is also possible to allow the light to pass through the electrode itself and make it enter the light-receiving layer.

[0005]

However, in the conventional Schottky barrier type GaN-based light receiving element, the light receiving layer i
GaN is exclusively used as the material of the layer, and as a result, only light having a short wavelength of 365 nm (= wavelength corresponding to the band gap of GaN) or less can be detected. That is, there has been no conventional Schottky barrier type GaN-based light receiving element capable of detecting light having a wavelength longer than 365 nm.

An object of the present invention is to provide a Schottky barrier type GaN-based light receiving element that solves the above problems and can detect light having a wavelength longer than 365 nm.

[0007]

The present invention has the following features. (1) A Schottky barrier type semiconductor light receiving device having a structure in which an i layer made of a GaN-based semiconductor crystal is used as a light receiving layer, and a Schottky electrode is provided on the upper surface of the i layer, wherein the i layer is , Which has a smaller bandgap than GaN
_{x Ga y Al z N (0} <x ≦ 1,0 ≦ y <1,0 ≦ z <
1) A GaN-based semiconductor light receiving element characterized by comprising:

(2) Between the i layer and the Schottky electrode,
The surface layer made of a GaN-based semiconductor crystal is interposed, and at least a portion of the surface layer in contact with the Schottky electrode is made of a GaN-based semiconductor crystal having a band gap larger than that of the i-layer. GaN-based semiconductor light receiving element.

(3) As the surface layer approaches from the i-layer side to the Schottky electrode side, the same composition as the i-layer changes to a composition having a larger band gap in a stepwise or stepless manner. The GaN-based semiconductor light-receiving element according to (2) above, which is a layer.

(4) The i-layer and a GaN-based semiconductor crystal layer having a bandgap larger than that of the i-layer and a low carrier concentration are alternately laminated to form a superlattice structure. The GaN-based semiconductor light receiving element according to (1) or (2) above, wherein the i layer is a light receiving layer in the lattice structure.

(5) The Ga according to (4), wherein the uppermost layer of the superlattice structure is the GaN-based semiconductor crystal layer having a band gap larger than that of the i layer and a low carrier concentration.
N-based semiconductor light receiving element.

In the present invention, the GaN-based semiconductor means In _a
Ga _b Al _c N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1,
a + b + c = 1), and the composition ratio (mixed crystal ratio) is arbitrary, for example, AlN, Ga
N, AlGaN, InGaN and the like are listed as important compounds. In this specification, the range of the composition ratio is limited by adding a condition such as "a band gap is larger than that of the i layer" to the GaN-based semiconductor.

The i layer is a general term for a low carrier concentration layer and means an n-type low carrier concentration layer or a p-type low carrier concentration layer. Low carrier concentration means 1 × 10 ¹³ c
It is about m ⁻³ to 1 × 10 ¹⁷ cm ⁻³ . Since the GaN-based semiconductor is undoped and exhibits n-type conductivity, the i-layer has n-type conductivity.
It is preferably a mold. Therefore, in the following, the i layer is
The structure of the device will be described as a low carrier concentration layer made of a GaN-type crystal having a p-type.

Further, in this specification, in order to clearly describe the structure of the light receiving element, terms such as "top surface of layer" indicating the vertical direction are used. This is to clearly describe both sides of each layer, and does not limit the absolute vertical direction of the element structure, nor does it limit the mounting direction (posture at the time of mounting) of the element.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The light-receiving element of the present invention has an i-layer 1 made of a GaN-based crystal as a light-receiving layer, and an upper surface of the i-layer 1, as schematically shown in FIG. This is a Schottky barrier type GaN-based light-receiving element having an element structure in which a Schottky electrode P1 is provided in the. And the i
As a material of the layer 1, a composition ratio of In _x Ga _y Al _z N (0 <is set so that the band gap is smaller than that of GaN.
x ≦ 1, 0 ≦ y <1, 0 ≦ z <1) is used.
As a result, the light receiving element can detect light having a wavelength longer than the wavelength of 365 nm corresponding to the band gap of GaN.

In the example of FIG. 1, the laminated structure of the device itself is the same as that of the conventional one, and Ga is formed on the sapphire substrate B1.
N-type GaN crystal layer (Si-doped high carrier concentration layer) 2 and i layer (light-receiving layer) via the N-based low temperature growth buffer layer B2
1 are sequentially deposited by vapor phase epitaxy, the i layer 1 is partially removed by RIE, and the n-type GaN crystal layer 2 is formed.
Is exposed, and the Schottky electrode P is formed on the upper surface of the i layer 1.
1, the ohmic electrode P2 is formed on the exposed surface of the n-type GaN-based crystal layer 2, respectively. The light L to be detected passes through the Schottky electrode P1 and enters the i layer.

In _x Ga _y Al _z used as a material for the i layer
As for N, each composition ratio x, y, z may be selected from the range of (0 <x ≦ 1, 0 ≦ y <1, 0 ≦ z <1) so that the bandgap is smaller than that of GaN. Among them, as a particularly preferable material for the i layer, the Al composition ratio z =
0, In _x Ga _{1-x represented} as Ga composition ratio y = _1-x
N (0 <x ≦ 1) is included. Considering the actual crystal quality of In _x Ga _1-x N, etc., the preferable range of In composition ratio x is 0 <x ≦ 0.5, more preferably 0 <x.
≦ 0.2 can be mentioned. For example, i is a specific numerical value.
When In _0.1 Ga _0.9 N is used as the material of the layer, the wavelength of light that can be detected is 420 nm, which corresponds to the band gap, and a wavelength shorter than that.

The inventors of the present invention have made In _x Ga _y A as described above.
When l _z N was used as the material for the i layer, the following additional problems were found, and it was a further task to alleviate them. In _x Ga _y Al _z N as described above, especially In _x Ga _{1 -x}
Since N has a high n-type carrier concentration even if it is undoped, it is difficult to make Schottky contact. That is, there is a possibility of ohmic contact. In _x Ga _y Al _z N as described above, especially In _x Ga _{1 -x}
Since N is thermally weak, N atoms may be desorbed at a high temperature after completion of growth, and n-type may be further promoted.

In the present invention, in order to solve the above-mentioned problems, as shown in FIG. 2, the i layer 1 and the Schottky electrode P1 are formed.
Further, a surface layer S made of a GaN-based semiconductor crystal is further interposed therebetween. The surface layer S is at least a portion of the entire layer in contact with the Schottky electrode P1 (hereinafter,
“Schottky contact portion”) is a GaN-based semiconductor having a bandgap larger than that of the i layer. That is, the entire surface layer S may be homogeneously composed of a GaN-based semiconductor having a bandgap larger than that of the i layer, or as it approaches the Schottky electrode side from the i layer side,
It may be configured to change stepwise or steplessly from the same composition as the i layer to a composition having a larger band gap.

By interposing the surface layer configured as described above, it becomes possible to secure sufficient Schottky contact as a light receiving element as shown in a band diagram in FIG. It is considered that the surface layer serves as a barrier against holes generated in the i layer due to light reception. However, by making the surface layer thin, holes can pass through the surface layer by tunneling.

The diagram shown in FIG. 3 (a) is a diagram in the case where the entire surface layer S is homogeneously constituted by a GaN-based semiconductor having a band gap larger than that of the i layer. E _c is the energy at the bottom of the conduction band, E _v is the energy at the top of the valence band, and E _F is the Fermi level. As shown in the figure, a sufficient Schottky barrier height is secured at the interface with the electrode P1.

The diagram shown in FIG. 3B shows that the surface layer S has a structure in which the composition is continuously changed from the same composition as the i layer to a composition having a larger bandgap as the surface layer S is closer to the Schottky electrode side. 3D is a diagram in the case of changing steplessly, and in addition to the characteristics of FIG. 3A, there is no step (energy gap) at the boundary between the surface layer S and the i layer 1, and it occurs in the i layer. The hole thus formed can reach the Schottky electrode more smoothly. The change in the composition gradient of the surface layer may be a linear change or a change that draws an arbitrary curve. Further, even if the composition gradient of the surface layer is changed in multiple steps, the same operational effect as in stepless change can be obtained.

Of the materials for the surface layer, at least the material used for the Schottky contact portion is the material for the i layer In _x Ga _y
Depending on the composition of _{Al z N, In d Ga e} Al f N (0 ≦ the band gap than is selected to be greater
d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1). However, since the above problem is caused by the presence of In composition, a preferable material In _d Ga _e Al _f N is (In composition ratio d = 0, Ga composition ratio e = 1-f) It indicated the _{Al f Ga 1-f N (} 0 <f ≦ 1) can be mentioned. Further, considering the crystal quality of the Al _f Ga _{1 -f} N, etc., the preferable range of the Al composition ratio f is 0 ≦ f ≦
0.5, and more preferably 0 ≦ f ≦ 0.2.
Among them, GaN having an Al composition ratio f = 0 is a preferable material for the surface layer because crystals of good quality are easily obtained.

The surface layer has a low carrier concentration similar to that of the i layer,
It is preferably formed as a conductive layer, and the thickness of the layer is preferably about 1 nm to 50 nm from the viewpoint of obtaining the tunnel effect of holes.

In the present invention, as described above, In _x Ga _y Al _z N is used as the material of the i layer. The thickness of the i layer is
It is preferably about 5 nm to 500 nm, particularly preferably about 10 nm to 100 nm. However, a GaN-based crystal containing an In composition,
In particular, In _x Ga _1-x N is difficult to grow into a thick film as a crystal layer of good quality, and if the layer thickness is grown to more than several tens of nm, composition variation occurs and the crystal quality deteriorates. Therefore, it is difficult to secure a light receiving layer having a sufficient thickness with good crystal quality.

Therefore, in the present invention, as a preferable mode for obtaining the above-mentioned i layer with good crystal quality and sufficient thickness, as shown schematically in FIG. 4, the band gap is larger than that of the i layer. And the GaN-based semiconductor crystal layers (3a, 3b, 3c) having good crystal growth and the i layers (1a, 1b, 1)
c) and c) are alternately laminated to form a superlattice structure, and the i-layer separated and present in the superlattice structure is used as the light-receiving layer.
The carrier concentration of the GaN-based semiconductor crystal layer is as low as that of the i layer. This makes it possible to make the i-layer sufficiently thick as a whole, generate more carriers, and obtain good sensitivity.

As the [GaN-based semiconductor having a band gap larger than that of the i layer and good crystal growth property] used for the above superlattice structure, the band may be changed depending on the composition of the material In _x Ga _y Al _z N of the i layer. In _d G to meet the gap condition
a _e Al _f N (0 ≤ d ≤ 1, 0 ≤ e ≤ 1, 0 ≤ f ≤ 1) may be selected, but as a material satisfying the condition that the crystal growth property is good, GaN Is mentioned.
Hereinafter, the superlattice structure will be described by taking an alternate lamination of i layers and GaN layers as an example, but the combination of materials is not limited to this.

The number of superlattice pairs formed by (i layer / GaN layer) is not limited, but the element structure is preferably about 2 to 500 pairs, more preferably about 10 to 100 pairs. The thickness per layer due to the superlattice structure is 0.
1 nm to 50 nm, more preferably 0.5 nm to 20 n
m.

Although the above-mentioned surface layer may be separately interposed between the superlattice structure and the Schottky electrode, the uppermost layer of the superlattice structure is a GaN layer, and the GaN layer and the surface layer are used in common. May be. Further, the uppermost layer of the superlattice structure may be an i-layer, and a surface layer having a composition gradient from the composition of the i-layer to GaN may be formed thereon.

Each part common to the light receiving element of the present invention will be described. When a device structure is formed on a crystal substrate, the substrate may be any one that can grow a GaN-based crystal, such as sapphire (C face, A face, R face), SiC (6H, 4H, 3).
C), Si, spinel, ZnO, GaAs, NGO, G
Although an aN-based material (particularly GaN) can be used, other materials may be used as long as they correspond to the object of the present invention. The plane orientation of the substrate is not particularly limited, and may be a just substrate or a substrate having an off angle.

As shown in FIGS. 1 and 2, when a GaN-based crystal layer such as a high carrier concentration layer is formed on a crystal substrate,
A buffer layer may be interposed if necessary. The buffer layer material and the film forming method are not limited, but a GaN-based low temperature buffer layer in which GaN, AlN and the like are grown at a low temperature in the same crystal growth apparatus is preferable.

Further, on the crystal substrate, a high carrier concentration layer,
When growing a GaN-based crystal layer such as an i-layer, various techniques for reducing dislocation density may be appropriately introduced,
For example, the following structure may be provided on the surface of the crystal substrate. (Ii) A structure in which a mask layer (SiO ₂ or the like is used) is formed as a stripe pattern on a crystal substrate so that a conventionally known selective growth method (ELO method) can be carried out. (B) A structure in which dot-shaped and stripe-shaped irregularities are formed on the crystal substrate so that the GaN-based crystal can undergo lateral growth or facet growth. These structures and the buffer layer may be combined appropriately.

Among the structures for reducing dislocation density, the above-mentioned (ro) is a preferable structure without using a mask layer, and particularly, a structure having stripe-shaped unevenness is preferable. The longitudinal direction of the stripe may be arbitrary, but if the direction is set to <11-20> for a GaN-based crystal grown by embedding the stripe, lateral growth is suppressed, and oblique facets such as {1-101} planes are suppressed. Are easily formed. As a result, dislocations propagating in the C-axis direction from the substrate side are laterally bent at this facet surface, and it becomes difficult for them to propagate upward, and a low dislocation density region is formed.

On the other hand, when the longitudinal direction of the stripe is the <1-100> direction for the growing GaN-based crystal,
The GaN-based crystal that has started to grow from the upper portion of the convex portion tends to grow laterally at a high speed and become a GaN-based crystal layer with the concave portion left as a cavity.

As a method for growing a GaN-based crystal layer, HV is used.
The PE method, MOVPE method, MBE method and the like can be mentioned. The HVPE method is preferable when forming a thick film, but the MOVPE method or MBE method is preferable when forming a thin film.

High carry shown in the example of the device structure of FIGS.
The concentration layer 2 is a contact for forming an ohmic electrode.
Layer, has the same conductivity type as the i layer, and has a carrier concentration
The degree is 1 × 10¹⁷cm^-3~ 1 x 10²⁰cm^-3Degree, especially
1 x 10¹⁸cm^-3~ 1 x 10 ¹⁹cm^-3A degree is preferable.

The Schottky electrode may be any electrode in the state where a Schottky barrier is generated so as to function as a light receiving element, and the known method is used for forming the electrode and the shape of the electrode such as a comb-shaped electrode and a transparent electrode. You can refer to it. Further, when the light to be received is incident through the crystal substrate, it may be an opaque electrode. The material of the Schottky electrode is not limited, and examples thereof include Au, Pt, Ni, Pb and the like. Also, these materials may be used in combination. The material of the ohmic electrode is not limited, and examples thereof include Al / Ti, Au / Ti, and Ti. Also, these materials may be used in combination.

[0038]

EXAMPLES Example 1 In this example, the light receiving element of FIG. 2 was actually manufactured. A C-plane sapphire substrate (2-inch diameter wafer: substrate B1 of FIG. 2 will be obtained by cutting later) is mounted on the MOVPE apparatus,
After heating to 1100 ° C. in a hydrogen atmosphere and performing thermal etching, the temperature is lowered to 450 ° C., Ga raw material trimethylgallium (hereinafter TMG) and N raw material ammonia are flown, and the GaN low temperature growth buffer layer B2 is formed to a thickness. Thirty
nm was grown.

(Formation of High Carrier Concentration Layer 2) Temperature: 10
The temperature is raised to 00 ° C., TMG and ammonia are added, and silane as a dopant material is flown to form n-type G as the high carrier concentration layer 2.
The aN layer was grown to a thickness of 4.5 μm. The carrier concentration of the high carrier concentration layer was 2 × 10 ¹⁸ cm ⁻³ .

(Formation of i layer) The temperature is set to 700 ° C. and In
Raw materials trimethylindium (hereinafter TMI), TMG, and ammonia were caused to flow to grow an undoped In _0.1 Ga _0.9 N crystal layer (light receiving wavelength 420 nm) to a thickness of 50 nm,
The i layer 1 was used. The carrier concentration of the i layer is 1 × 10 ¹⁶ cm
^-3 or less.

(Formation of surface layer) The temperature is set to 1000 ° C.,
An undoped GaN crystal layer was grown to a thickness of 10 nm by flowing TMG and ammonia to form a surface layer S.

The above-mentioned laminated body was taken out of the apparatus and 1.2 m
The high carrier concentration layer 2 was partially exposed by etching from the upper surface so that the central portion of the element remained as a cylindrical shape having a diameter of 900 μm with respect to the outer peripheral portion of the portion to be the m-square chip.

Then, a comb-shaped Schottky electrode P1 having a width of 2 μm and an interval of 2 μm made of Au / Ni was formed on the upper surface of the i layer by photolithography and vapor deposition. An ohmic electrode P2 made of Al / Ti was formed on the exposed upper surface of the high carrier concentration layer. Through the above steps, a light receiving element structure repeatedly formed in a matrix on a sapphire wafer was obtained, and this was divided into individual 1.2 mm square bare chips to obtain a light receiving element according to the present invention. The evaluation of the light receiving element will be described later together with other examples.

Example 2 In this example, as shown in the band diagram of FIG. 3B, the light receiving element was manufactured in the same manner as in Example 1 except that the composition of the surface layer was graded. The thickness of the surface layer is 20 nm, and by continuously controlling the growth conditions such as the amount of raw material supply and the temperature from the completion of the formation of the i layer,
The composition was changed steplessly and linearly from the composition In _0.1 Ga _0.9 N of the i layer to the composition GaN of the Schottky contact portion. The evaluation of the light receiving element will be described later together with other examples.

Example 3 In this example, as shown in FIG. 4, In _0.1 Ga _0.9 N
Similar to Example 1 except that a superlattice structure composed of the (i layer) and a GaN layer having a low carrier concentration was formed,
The light receiving element was manufactured. The superlattice structure is formed on the GaN high carrier concentration layer 2 with the i layer as the lower layer side, and
_The number of pairs of ( _0.1 Ga _0.9 N: 2 nm / GaN layer: 5 nm) was 50, the uppermost layer was also used as a GaN layer, and the uppermost layer was also used as a surface layer. The evaluation of the light receiving element will be described later together with other examples.

Example 4 In this example, the uppermost GaN layer of the superlattice structure of Example 3 was used as a surface layer having a thickness of 10 nm, and within the layer thickness, the composition of the i layer In _0.1 Ga _0.9. The light-receiving element was manufactured in the same manner as in Example 3 except that the composition was changed steplessly and linearly from N to the composition GaN of the Schottky contact portion. The evaluation of the light receiving element will be described later together with other examples.

(Evaluation of Light-Receiving Element) The light-receiving sensitivity of each light-receiving element obtained in Examples 1 to 4 was measured for each wavelength. The light receiving sensitivity characteristics of the light receiving element of each example are shown in FIG.
This is shown in the graph of FIG. The light receiving element of the first embodiment is shown in FIG.
As shown in (a), the light-receiving peak wavelength was 410 nm, and the light-receiving sensitivity was 0.04 A / W. As shown in FIG. 5B, the light receiving element of Example 2 had a light receiving peak wavelength of 410 nm and a light receiving sensitivity of 0.06 A / W. From this result, it is understood that the light receiving sensitivity is further improved by the composition gradient of the surface layer. As shown in FIG. 6A, the light receiving element of Example 3 has a light receiving peak wavelength of 410
nm, and the photosensitivity was 0.08 A / W. From this result, it can be seen that the photosensitivity is further improved by the superlattice structure. The light receiving element of the fourth embodiment is shown in FIG.
As shown in, the light-receiving peak wavelength was 410 nm, and the light-receiving sensitivity was 0.12 A / W. From this result, it is understood that the light receiving sensitivity was further improved by combining the compositional gradient of the surface layer and the superlattice structure of the light receiving layer.

[0048]

As described above, the light receiving element according to the present invention is capable of detecting light having a wavelength longer than the light having a wavelength of 365 nm, and is not available in the prior art as a GaN-based Schottky type light receiving element. Is. Also, the interposition of the surface layer, i
By imparting a preferable configuration such as layer multiplexing (superlattice structure), the i-layer contains an In composition,
It has become possible to obtain a light-receiving element having higher light-receiving sensitivity.

[Brief description of drawings]

FIG. 1 is a schematic view showing a structural example of a light receiving element according to the present invention. Hatching is appropriately applied to distinguish the regions. The following figures are also the same.

FIG. 2 is a schematic diagram showing a structural example of a light receiving element of the present invention to which a surface layer is added.

FIG. 3 is a diagram showing a band diagram in the vicinity of a Schottky junction when a surface layer is added to the light receiving element of the present invention.

FIG. 4 is a schematic diagram showing an example of a device structure when an i layer is alternately grown together with a GaN-based crystal layer to form a superlattice structure in the present invention. The thickness of each layer and the number of pairs in the illustrated superlattice structure are different from the actual ones for the sake of explanation.

FIG. 5 is a diagram showing a light receiving sensitivity characteristic of a light receiving element manufactured in an example of the present invention. FIG. 5A shows the light receiving sensitivity characteristic of the light receiving element of the first embodiment, and FIG. 5B shows the light receiving sensitivity characteristic of the light receiving element of the second embodiment.

FIG. 6 is a diagram showing a light receiving sensitivity characteristic of a light receiving element manufactured in an example of the present invention. FIG. 6A shows the light receiving sensitivity characteristic of the light receiving element of the third embodiment, and FIG. 6B shows the light receiving sensitivity characteristic of the light receiving element of the fourth embodiment.

FIG. 7 is a schematic view showing a structure of a conventional Schottky barrier type GaN-based light receiving element.

[Explanation of symbols]

1 i layer 2 High carrier concentration layer P1 Schottky electrode P2 ohmic electrode L Light to be detected

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroaki Okakawa             4-3 Ikejiri, Itami City, Hyogo Prefecture Mitsubishi Electric Cable             Industrial Co., Ltd. Itami Works (72) Inventor Takashi Tsunekawa             4-3 Ikejiri, Itami City, Hyogo Prefecture Mitsubishi Electric Cable             Industrial Co., Ltd. Itami Works F-term (reference) 5F049 MA05 MB07 NA01 PA04 QA16                       QA20 SE05 SE11 SS01

Claims (5)

[Claims] 1. A Schottky barrier type semiconductor light receiving element having an i layer made of a GaN-based semiconductor crystal as a light receiving layer and having a structure in which a Schottky electrode is provided on the upper surface of the i layer. The layer is In _x G, which has a smaller bandgap than GaN.
a _y Al _z N characterized by comprising the (0 <x ≦ 1,0 ≦ y <1,0 ≦ z <1), GaN -based semiconductor light-receiving element. 2. Ga is provided between the i layer and the Schottky electrode.
The surface layer made of an N-based semiconductor crystal is interposed, and at least a portion of the surface layer in contact with the Schottky electrode is made of a GaN-based semiconductor crystal having a band gap larger than that of the i layer. GaN-based semiconductor light receiving element. 3. A layer in which the surface layer changes stepwise or steplessly from the same composition as the i layer to a composition having a larger band gap as the surface layer approaches from the i layer side to the Schottky electrode side. The GaN-based semiconductor light receiving element according to claim 2. 4. The superlattice structure is formed by alternately stacking the i-layer and a GaN-based semiconductor crystal layer having a bandgap larger than that of the i-layer and a low carrier concentration, thereby forming a superlattice structure. The GaN-based semiconductor light receiving element according to claim 1, wherein the i layer is a light receiving layer in the structure. 5. The G having the uppermost layer of the superlattice structure having a larger bandgap and a lower carrier concentration than the i-layer.
The GaN-based semiconductor light-receiving element according to claim 4, which is an aN-based semiconductor crystal layer.