JP2647631B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device comprising a Gunn diode used for microwave or millimeter-wave oscillation, and more particularly to a semiconductor device capable of significantly improving conversion efficiency.

[0002]

2. Description of the Related Art Generally, when a high electric field is applied to GaAs or the like, the drift velocity of conduction electrons increases up to a certain electric field intensity, but when a certain critical value is exceeded, the drift velocity decreases. It is known that it has the property of sex differential resistance. Gunn diodes utilizing the negative differential resistance properties of GaAs are widely used as microwave or millimeter-wave solid-state oscillation devices.

FIG. 8 is a diagram showing the relationship between the electric field strength and the drift velocity of conduction electrons when a high electric field is applied to GaAs or the like. The horizontal axis E represents the electric field strength, and the vertical axis V represents the drift velocity. ing. In FIG. 8, the electric field intensity has a critical value Et.
When h is smaller than h, the differential resistance, which is an amount inversely proportional to dV / dE, has a positive value. However, when the electric field strength becomes larger than the critical value Eth, the drift velocity becomes smaller.
The differential resistance will have a negative value. This is called negative differential resistance. This property of having negative differential resistance is caused by Ga
When As has two energy states and the electric field strength is smaller than the critical value Eth, most of the conduction electrons are in the low energy state where the effective mass is small and the mobility is large, but the electric field strength is lower than the critical value Eth. If the energy becomes larger, the conduction electrons transition to a high energy state in which the effective mass is large and the mobility is small due to the energy given by the electric field.

Hereinafter, a conventional gun diode will be described with reference to the drawings. FIG. 9 is a configuration diagram showing an example of the structure of a conventional Gunn diode. In FIG. 9, a conventional Gunn diode is an active layer n made of a compound semiconductor.
The semiconductor device includes a type layer 901, n ⁺ -type layers 903 and 905 made of a compound semiconductor sandwiching the n-type layer 901, and electrode metals 907 and 909 joined to the n ⁺ -type layers 903 and 905. Here, the electrode metal 907 is on the cathode side, and the electrode metal 909 is on the anode side.

Next, the distribution of the donor impurity concentration in the n-type layer 901, the n ⁺ -type layer 903 and the n ⁺ -type layer 905 is shown in FIG. FIG. 10 shows an n-type layer 901, an n ⁺ -type layer 903 and an n-type layer 903.
^The vertical axis indicates the donor impurity concentration of the ⁺ type layer 905, and the electrode metal 9
The bonding surface 07 and the n ⁺ -type layer 903 as an origin, the electrode metal 9
The abscissa indicates the distance traveled in the direction of the bonding surface between the substrate 09 and the n ⁺ type layer 905. 10, when the distance is 0 to a, the n ⁺ -type layer 903 shown in FIG.
The portions between b and c correspond to the n ⁺ -type layers 905, respectively. The donor impurity concentration n ₂ of the n ⁺ -type layer 903 and the n ⁺ -type layer 905 depends on the n ⁺ -type layer 903 and the electrode metals 907 and n ⁺
The height is sufficiently high so that the mold layer 905 and the electrode metal 909 can be easily ohmic-joined.

For the conventional Gunn diode having the structure described above, the width of the n-type layer 901 as the active layer and the donor impurity concentration n ₁ of the n-type layer 901 are selected to appropriate values. When an appropriate DC voltage is applied between the metal 907 and the electrode metal 909, the concentration of conduction electrons called a gun domain on the cathode side of the n-type layer 901 is higher than that of the surroundings due to the property of the negative differential resistance described above. A region (electron storage layer) or a region where a region with a high concentration of conduction electrons and a region with a small concentration of conduction electrons are adjacent to each other (an electric double layer) occurs. The gun domain generated on the cathode side moves toward the anode side and disappears when reaching the n ⁺ type layer 905 on the anode side,
At the same time, a new gun domain is created on the cathode side. By repeating this phenomenon, an AC current appears between the electrode metal 907 and the electrode metal 909 so as to be superimposed on the DC current. The frequency of the AC current, that is, the natural frequency of the Gunn diode, is approximately determined by the speed of the Gunn domain in the n-type layer 901. The speed of the Gunn domain is approximately equal to the saturation speed Vs of the conduction electrons shown in FIG. Therefore, assuming that the width of the n-type layer 901 is La, the natural frequency f of the Gunn diode is given by f = Vs / La (1). Therefore, the appropriate width La of the n-type layer 901, that is, the active layer, is given by La = Vs / f (2) as a function of the expected frequency f.

As described above, the Gunn diode is used for microwave or millimeter wave band oscillation. For example, by appropriately arranging a Gunn diode in a cavity resonator or the like, high-frequency electromagnetic waves such as microwaves can be extracted from the Gunn diode. Such an oscillator using a Gunn diode is called a Gunn oscillator, and how much AC output of the input DC power can be obtained is as follows.
It is the most important figure of merit of gun oscillator. This index is
It is called conversion efficiency, and it is required to improve this value.

[0008]

However, in the conventional Gunn diode, there is a problem that a dead zone described later is generated in the active layer, which impairs the conversion efficiency of the Gunn diode. Hereinafter, the dead zone will be described in detail.

A conventional Gunn diode has an n ⁺
Although it has an nn ⁺ structure, the place where the cancer domain occurs is not the junction surface between the n-type layer 901 as the active layer and the n ⁺ -type layer 903 on the cathode side, but the n-type layer 901 from the junction surface. It is generally known that the position is a certain distance toward the side.

FIG. 11 is a diagram simulating the movement of a gun domain in a conventional n ⁺ nn ⁺ structure gun diode by a computer experiment. n-type layer, the conduction electron density of the cathode side of the n ⁺ -type layer and the anode side of the n ⁺ -type layer on the vertical axis, the joint surfaces of the cathode electrode and the cathode side of the n ⁺ -type layer as the origin, the anode electrode and the anode side The horizontal axis indicates the distance that the n ⁺ -type layer advances in the direction of the bonding surface. When the distance is about 0.5 μm or less, about 0.2 μm is added to the n ⁺ type layer 903 shown in FIG.
Between about 5 μm and about 2.3 μm, about 2.3
μm or more corresponds to the n ⁺ -type layer 905, respectively. As shown in FIG. 11, between about 0.6 μm to about 1.2 μm
(A region in the figure), that is, it can be seen that there is no cancer domain between a position where a certain distance has passed from the junction surface between the n-type layer 901 and the n ⁺ -type layer 903 on the cathode side.

This is explained for the following reasons.

The conduction electrons entering the n-type layer 901 which is the active layer from the n ⁺ -type layer 903 on the cathode side include the n-type layer 9.
01, energy is given from an electric field applied between the metal electrode 907 (cathode electrode) and the metal electrode 909 (anode electrode). As described above, the conduction electrons transition from the low energy state to the high energy state due to this energy, and have the property of negative differential resistance. However, the conduction electrons immediately after entering the n-type layer 901 do not have sufficient energy to transition from the low energy state to the high energy state, and therefore cannot have the property of negative differential resistance. Accordingly, the conduction electrons gain sufficient energy to transition from the low energy state to the high energy state while traveling in the n-type layer 901 for a certain distance, and have a property of negative differential resistance. Become. Then, at that time, a cancer domain is formed. Therefore, a gun domain is not formed between positions where the n-type layer 901 and the n ⁺ -type layer 903 on the cathode side advance a predetermined distance from each other.

As described above, the region between the junction surface of the active layer and the n ⁺ -type layer on the cathode side and the position where the gun domain actually occurs is a region where the gun domain does not exist. I'm calling The existence of the dead zone substantially reduces the width of the active layer, and changes the characteristics of the Gunn diode. Therefore, it is desirable to minimize or eliminate the dead zone. In particular, in the case of a Gunn diode having a high frequency of 40 GHz or more, since the width of the active layer is required to be extremely small from the above equation (2), the width of the dead zone is smaller than the width of the active layer. The occupation ratio becomes very large, and the characteristics of the Gunn diode are greatly impaired.
Therefore, the existence of the dead zone is a serious hindrance to the conversion efficiency.

Therefore, as a method for eliminating the dead zone, a structure in which the n ⁺ -type layer on the cathode side is removed and an electrode metal is directly bonded to the n-type layer as an active layer has been attempted. FIG. 12 is a configuration diagram showing an example of a Gunn diode having a structure in which an electrode metal is directly joined to an active layer. In FIG. 12, this Gunn diode has an active layer of n
Type layer 1201, n ⁺ type layer 1203, n type layer 1201
And an electrode metal 1205 and 1207 bonded to the n ⁺ -type layer 1203.
7 is bonded to the n ⁺ -type layer 1203, while the cathode-side electrode metal 1205 is directly bonded to the n-type layer 1201. With such a structure, the n-type layer 1201
And the metal electrode 1205 are Schottky junctions.
By optimizing the characteristics of the Schottky junction, the dead zone can be eliminated and the conversion efficiency can be improved. However, the Schottky junction has a problem that its reproducibility in production is lower than that of the ohmic junction and its characteristics are extremely sensitive to temperature, so that its reliability is low.

The present invention has been made in view of the above circumstances, and has as its object to reduce the dead zone while maintaining the n ⁺ nn ⁺ structure, which is the structure of a conventional Gunn diode, and to improve the reliability. It is an object of the present invention to provide a Gunn diode semiconductor device capable of significantly improving the conversion efficiency without impairing the semiconductor device.

[0016]

According to a first aspect of the present invention, there is provided an active layer made of a compound semiconductor, a low-concentration layer provided on a part of the active layer, and an active layer. In a semiconductor device including a Gunn diode having a sandwiching electrode, the width of the low-concentration layer is 0.156x, where x is the ratio of the concentration of the active layer to the concentration of the low-concentration layer.
² −0.862x + 1.24 (μm) or more −0.281
x ² + 1.11x−0.56 (μm) or less.

According to a second aspect of the present invention, there is provided a semiconductor device comprising a Gunn diode having an active layer made of a compound semiconductor, a low-concentration layer provided on a part of the active layer, and an electrode sandwiching the active layer. If the ratio between the concentration of the active layer and the concentration of the low concentration layer is x, the width of the low concentration layer is 0.
250x ² -1.28x + 1.73 (μm) or more -0.
219 × ² + 0.888 × −0.43 (μm) or less.

The above electrode has a high donor impurity concentration of n ^{+ in} that a stable ohmic junction can be obtained.
It is desirable to be formed of a mold layer and a metal.

[0019]

According to the first aspect of the present invention, assuming that the ratio of the concentration of the active layer to the concentration of the low concentration layer is x, the width of the low concentration layer is
0.250x ² -1.28x + 1.73 (μm) or more-
Since it is not more than 0.219 × ² + 0.888 × −0.43 (μm), the dead zone can be reduced, and the conversion efficiency can be improved by at least 30% compared with the case where there is no low concentration layer.

According to the structure of the second aspect of the present invention, assuming that the ratio of the concentration of the active layer to the concentration of the low concentration layer is x, the width of the low concentration layer is
0.250x ² -1.28x + 1.73 (μm) or more-
Since it is not more than 0.219 × ² + 0.888 × −0.43 (μm), the dead zone can be reduced, and the conversion efficiency can be improved by at least 50% compared to the case where there is no low concentration layer.

According to the structure of the present invention, n ⁺ nn ⁺
Since the structure is maintained, the junction with the electrode metal becomes an ohmic junction, and the electrode can be manufactured with high reproducibility.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of the structure of the Gunn diode of the present invention. In FIG. 1, a Gunn diode according to the present invention includes an n-type layer 101 which is an active layer made of a compound semiconductor, and a low-concentration layer provided on a part of the n-type layer 101.
(Hereinafter referred to as notches layer) n ^- -type layer 111, sandwiching the n-type layer 101, made of a compound semiconductor n ⁺ -type layer 103
, And 105, and electrode metals 107 and 109 that are bonded to the n ⁺ -type layers 103 and 105, respectively. Here, the electrode metal 107 is on the cathode side, and the electrode metal 109 is on the anode side.

Next, the n-type layer 101, the n ⁻ -type layer 111, n
FIG. 2 shows the distribution of the donor impurity concentration of the ⁺ type layer 103 and the n ⁺ type layer 105. FIG. 2 shows the donor impurity concentration of the n-type layer 101, the n ⁻ -type layer 111, the n ⁺ -type layer 103, and the n ⁺ -type layer 105 on the vertical axis, and the origin at the junction surface between the electrode metal 107 and the n ⁺ -type layer 103. The horizontal axis indicates the distance that the electrode metal 109 and the n ⁺ -type layer 105 travel in the direction of the bonding surface. In FIG. 2, when the distance is between 0 and a, the n ⁺ -type layer 103 shown in FIG.
The portion between a and b corresponds to the n ⁺ -type layer 103, the portion between b and c corresponds to the n ⁺ -type layer 101, and the portion between cd and d corresponds to the n ⁺ -type layer 105. The donor impurity concentration n ₃ of the n ⁺ type layer 103 and the n ⁺ type layer 105 depends on the n ⁺ type layer 103 and the electrode metal 107.
The height is sufficiently high so that the n ⁺ -type layer 105 and the electrode metal 109 can be easily ohmic-joined.

When a DC voltage is applied between the electrode metal 107 and the electrode metal 109, the AC current appears to be superimposed on the DC current. This is based on the same phenomenon as the conventional Gunn diode. Description is omitted.

Next, the effect of providing the n ⁻ -type layer 111, that is, the notch layer will be described. At first,
The reason for providing the notch layer will be described.

FIG. 3 is a diagram simulating the above-described movement of the gun domain by a computer experiment.
3A shows the case of the Gunn diode of the present invention having a notch layer, and FIG. 3B shows the case of a conventional Gunn diode having no notch layer. Note that an n-type layer, an n ^- type layer,
Conduction electron concentration on the cathode side of the n ⁺ -type layer and the anode side of the n ⁺ -type layer on the vertical axis, the joint surfaces of the cathode electrode and the cathode side of the n ⁺ -type layer as the origin, the anode electrode and the anode side n
^The horizontal axis indicates the distance that the ⁺ -type layer advances in the direction of the bonding surface. As is clear from FIG. 3, the above-described dead zone (the area indicated by A in the figure) of the Gunn diode of the present invention having the notch layer is smaller than that of the conventional Gunn diode having no notch layer. .

This is due to the following reasons.

FIG. 4 is a graph showing the donor impurity concentration, the conduction electron concentration, and the electric field intensity near the dead zone in FIG. 3. The vertical axis represents the donor impurity concentration, the conduction electron concentration, or the electric field intensity. The horizontal axis indicates the distance from the cathode side to the anode side. In addition, FIG.
In the case of the gun diode of the present invention having a notch layer, FIG.
(b) shows the case of a conventional Gunn diode having no notch layer. In each case, the thick solid line indicates the donor impurity concentration, the thin solid line indicates the conduction electron concentration, and the broken line indicates the electric field intensity.

In FIG. 4, the donor impurity concentration in the gun diode of the present invention is larger than that of the conventional gun diode.
(Thick solid line in the figure) and the conduction electron concentration (thin solid line in the figure) show a large shift, and the shift distance is long. The distance ranges from about 0.5 μm to 0.9 μm. This is because the gun diode of the present invention shown in FIG.
By providing the notch layer, the n ⁺ type layer (a distance of about 0.5 μ
m or less) and the n ^- type layer (the distance is about 0.5 μm to 0.1 μm).
Boundary (range of about 9 μm) (at a distance of about 0.5 μm),
And n-type layer (distance in the range of about 0.9 μm or more) and n ⁻
This is because while the donor impurity concentration rapidly changes at the boundary of the mold layer (at a distance of about 0.9 μm), the conduction electron concentration cannot follow the sudden change in the donor impurity concentration.

Generally, assuming that the donor impurity concentration is N, the conduction electron concentration is n, and the electric field intensity is E, the electric field intensity E
And the difference N−n between the donor impurity concentration and the conduction electron concentration is expressed by the Poisson equation:

(Equation 1) There is. In addition, x is a distance, q is an electron charge amount, and ε is a dielectric constant.

According to equation (3), the electric field strength (dashed line in the figure) increases in the region where the conduction electron concentration (thin solid line in the figure) is higher than the donor impurity concentration (thick solid line in the diagram), and decreases in the opposite region. In addition, the larger the difference between the donor impurity concentration and the conduction electron concentration, the larger the change in the electric field intensity.

Therefore, in the Gunn diode of the present invention, by providing the notch layer, the difference between the above-mentioned donor impurity concentration and the conduction electron concentration is increased, and the shifted distance is lengthened, as compared with the conventional Gunn diode. So the expression
According to (3), the electric field strength near the dead zone can be increased.

On the other hand, as described above, the dead zone is the distance traveled by the conduction electrons in the active layer until the conduction electrons obtain energy from the electric field and have the property of negative differential resistance. Therefore, in the Gunn diode of the present invention, since the electric field strength near the dead zone can be increased, the conduction electrons obtain sufficient energy from the electric field to have the property of negative differential resistance with a shorter traveling distance than before. You can do it. Therefore, the dead zone can be shortened.

As described above, in the Gunn diode of the present invention, by providing the notch layer, the dead zone described above can be reduced and the conversion efficiency of the Gunn diode can be improved.

Next, optimization of the width of the notch layer will be described.

FIG. 5 is a graph showing the donor impurity concentration, the conduction electron concentration, and the electric field intensity near the dead zone in FIG. 3. The vertical axis indicates the donor impurity concentration, the conduction electron concentration, or the electric field intensity. The horizontal axis indicates the distance from the cathode side to the anode side. In addition, FIG.
FIG. 5B shows the case of the Gunn diode of the present invention in which the width of the notch layer is smaller than the optimum value, and FIG. 5B shows the case of the Gunn diode of the present invention in which the width of the notch layer is larger than the optimum value;
In each figure, the thick solid line indicates the donor impurity concentration, the thin solid line indicates the conduction electron concentration, and the broken line indicates the electric field intensity. Here, it is assumed that the characteristic shown in FIG. 4A has the optimum width of the notch layer.

As shown in FIG. 5A, when the width of the notch layer is small, the characteristics shown in FIG. 4A show that the donor impurity concentration is lower than when the width of the notch layer is optimum.
It can be seen that the distance between the (solid thick line in the figure) and the conduction electron concentration (thin solid line in the figure) is short, and the increase in the electric field strength (dashed line in the figure) ended immediately.

As shown in FIG. 5B, when the width of the notch layer is large, the change in the donor impurity concentration (thick solid line in the figure) is sufficiently followed by the conduction electron concentration (thin solid line in the figure). And the change of the electric field strength (broken line in the figure) becomes slow. For this reason, the maximum value of the electric field strength is almost the same as the optimal case shown in FIG. 4A, but the distance until the maximum value becomes long, and there is not much effect on the reduction of the dead zone. As described above, there is an optimum value for the width of the notch layer, and the effect of providing the notch layer is reduced if the width is larger or smaller than the optimum value. Therefore, it is necessary not only to provide the notch layer but also to optimize the width of the notch layer.

The present invention is characterized by finding the optimum width of the notch layer. This will be described below.

FIG. 6 is a diagram showing the relationship between the width of the notch layer and the conversion efficiency in the Gunn diode of the present invention by a numerical experiment. The conversion efficiency is shown on the vertical axis, and the width of the notch layer is shown on the horizontal axis. is there. FIG. 6A shows the case where the ratio N _A / N _n of the impurity concentration of the active layer (hereinafter referred to as N _A ) and the impurity concentration of the notch layer (hereinafter referred to as N _n ) is 1.6. ) Is N
If _A / N _n is 2.0, FIG. 6 (c), N _A / N _n indicates the case 2.4.

As shown in FIG. 6A, when the ratio N _A / N _n of the impurity concentration of the active layer to the impurity concentration of the notch layer is 1.6, when there is no notch layer (the width of the notch layer). Is 0 μm
In order to increase the conversion efficiency by at least 30% as compared with (), the width of the notch layer is 0.26 μm or more and 0.50 μm or more.
It is necessary to be below (the range indicated by A in the figure). Further, in order to increase the conversion efficiency by at least 50%, it is necessary to use 0.1.
It is necessary that the thickness be 33 μm or more and 0.43 μm or less (range indicated by B in the drawing). Further, the optimum value that maximizes the conversion efficiency is 0.36 μm.

As shown in FIG. 6B, when N _A / N _n is 2.0, in order to increase the conversion efficiency by at least 30% as compared with the case where there is no notch layer, the width of the notch layer is required. Is required to be not less than 0.14 μm and not more than 0.54 μm (the range indicated by A in the figure). Also, at least 50%
To increase the conversion efficiency, 0.18 μm or more and 0.47
μm or less (the range indicated by B in the figure). Further, the optimum value at which the conversion efficiency is highest is 0.28 μm.
It is.

As shown in FIG. 6C, when N _A / N _n is 2.4, the width of the notch layer is required to increase the conversion efficiency by at least 30% as compared with the case where the notch layer is not provided. Must be 0.07 μm or more and 0.49 μm or less (in the range indicated by A in the figure). Also, at least 50%
In order to increase the conversion efficiency, 0.11 μm or more and 0.44
μm or less (the range indicated by B in the figure). Further, the optimum value at which the conversion efficiency is highest is 0.20 μm.
It is.

[0045] From the above results, when the ratio N _A / N _n impurity concentration of the impurity concentration and the notch layer of the active layer and x, the thickness of the notch layer 0.156x ² -0.862x + 1.24 (μm) or more , -0.281x ² + 1.11x-0.56 (μm) or less, the conversion efficiency can be increased by at least 30% as compared with the case where the notch layer is not provided.

[0046] Further, the thickness of the notch layer 0.250x ² -1.28x + 1.73 (μm) or more, is set to be lower than or equal ^{-0.219x 2 + 0.888x-0.43 (μm} ), there is no notch layer The conversion efficiency can be increased by at least 50% as compared with the case where it is.

Next, an embodiment of a Gunn diode manufactured based on the notch layer optimized by the above numerical calculation will be described with reference to the drawings. FIG. 7 is a cross-sectional view of the Gunn diode of the present embodiment. With reference to FIG. 7, a method for manufacturing the gun diode of the present embodiment will be described. In this embodiment, FIG.
(b) corresponds to the case where N _A / N _n is 2.0, and the width of the notch layer is 0.28, which is calculated to be the highest conversion efficiency.
μm is adopted.

First, an n ⁺ -type GaAs layer 703 (dopant: Si, impurity concentration: 1 ×) is formed on one main surface of an n ⁺ -type GaAs substrate 701 (dopant: Si, impurity concentration: 1 × 10 ¹⁸ cm ⁻³ ). 10 ¹⁸ cm ⁻³ , width: 1.0 μm), n-type Ga
As active layer 705 (dopant: Si, impurity concentration: 1
× 10 ¹⁶ cm ⁻³ , width: 1.6 μm), n ⁻ -type GaAs notch layer 707 (dopant: Si, impurity concentration: 0.5 ×
10 ¹⁶ cm ⁻³ , width: 0.28 μm), n ⁺ type GaAs layer 7
09 (dopant: Si, impurity concentration: 1 × 10 ¹⁸ c
m ⁻³ , width: 0.3 μm) is epitaxially grown by MBE (molecular beam epitaxy).

Then, an electrode metal 711 (Au-Ge-Ni) is deposited on the other main surface of the n ⁺ -type GaAs substrate 701.
On the n ⁺ -type GaAs layer 709, an electrode metal 713 (Au
-Ge-Ni), a Gunn diode as shown in FIG. 7 is obtained.

Next, an oscillation experiment was performed using the Gunn diode manufactured by the above-described manufacturing method. As a result, the conversion efficiency was 5.2% and the output was 81 mW. As a comparative example, the n ⁻ -type GaAs notch layer 70
7 was formed, a Gunn diode without a notch layer in which the width of the n-type GaAs active layer 705 was increased by the width of the notch layer 707 (0.28 μm) was also manufactured, and an oscillation experiment was performed in the same manner. As a result, the conversion efficiency was 2%, and the output was 52 mW. Therefore, the conversion efficiency was increased by 160%.

Accordingly, from the above results, in the Gunn diode having the notch layer, when the ratio N _A / N _n of the impurity concentration of the active layer to the impurity concentration of the notch layer is x, the width of the notch layer is set to 0. .156x ² -0.862x + 1.2
4 ([mu] m) or more -0.281x ² + 1.11x-0.5
When the thickness is 6 (μm) or less, the dead zone can be reduced and the conversion efficiency can be improved by at least 30%. Also, the width of the notch layer, 0.250x ² -1.28
x + 1.73 (μm) or more−0.219 × ² + 0.88
By setting it to 8 × −0.43 (μm) or less, the dead zone can be reduced and the conversion efficiency can be improved by at least 50%. Further, since the n ⁺ nn ⁺ structure is maintained, the junction with the electrode metal becomes a sufficient ohmic junction, and the reliability is not impaired.

[0052]

As described above, according to the present invention, the notch layer is provided in a part of the active layer and the width thereof is optimized, so that the occurrence of a dead zone can be suppressed and the conversion efficiency can be significantly reduced. Can be improved. Furthermore, n ⁺ nn ⁺
Since the structure is maintained, high reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of the structure of a Gunn diode of the present invention.

FIG. 2 is a diagram showing an example of a donor impurity concentration of a Gunn diode of the present invention.

FIG. 3 is a diagram for explaining a gun domain in the gun diode of the present invention.

FIG. 4 is a diagram for explaining a gun domain in the gun diode of the present invention.

FIG. 5 is a diagram for explaining a gun domain in the gun diode of the present invention.

FIG. 6 is a diagram showing the relationship between the notch layer and the conversion efficiency in the Gunn diode of the present invention.

FIG. 7 is a sectional view showing an example of the structure of the Gunn diode of the present invention.

FIG. 8 is a diagram showing a relationship between electric field strength and conduction electrons in GaAs.

FIG. 9 is a configuration diagram showing an example of the structure of a conventional Gunn diode.

FIG. 10 is a diagram showing an example of a donor impurity concentration of a conventional Gunn diode.

FIG. 11 is a diagram for explaining a gun domain in a conventional gun diode.

FIG. 12 is a configuration diagram showing an example of the structure of another conventional Gunn diode.

[Explanation of symbols]

101, 705, 901, 1201 n-type layer (active layer) 103, 105, 703, 709, 903, 905, 1
203 n ⁺ type layers 107, 109, 711, 713, 907, 909, 1
205, 1207 Electrode metal 111, 707 n ^- type layer (low concentration layer or notch layer) 701 GaAs substrate

Claims (2)

(57) [Claims] 1. A semiconductor device comprising a gun diode having an active layer made of a compound semiconductor, a low-concentration layer provided on a part of the active layer, and an electrode sandwiching the active layer. When the concentration ratio of the concentration of the low concentration layer to x, the width of the low concentration ^{layer, 0.156x 2 -0.862x + 1.24 (μm} ) or more -0.281x ² + 1.11x-0.56 (μm) or less. 2. A semiconductor device comprising a gun diode having an active layer made of a compound semiconductor, a low-concentration layer provided on a part of the active layer, and an electrode sandwiching the active layer. When the concentration ratio of the concentration of the low concentration layer to x, the width of the low concentration ^{layer, 0.250x 2 -1.28x + 1.73 (μm} ) or more -0.219x ² + 0.888x-0.43 (μm) or less.