JPH09283444A - Planar dope hemt semiconductor wafer and planar dope hemt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the electron mobility of a two-dimensional electron gas in the case where metal organic vapor phase growth is used, to the same level as in the case where molecular beam epitaxy is used. SOLUTION: A channel layer is formed on a plane slightly inclined from a (100) plane of a GaAs substrate. An non-dope Alx Ga1-x As layer which is a first layer of a carrier supply layer is formed on the channel layer, and a high-density n-type planar dope layer which is a second layer of the supply layer is formed on the first layer. Then, a Aly Ga1-y As layer which is a third layer of the supply layer is formed on the second layer, thereby constituting a semiconductor wafer. In this case, the Al mixed crystal ratio x of the non- dope Alx Ga1-x As layer is set to 0.4 or greater. Using this semiconductor wafer, an HEMT is manufactured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a planar-doped H
Planar-doped HE used to manufacture EMT
Planar-doped H manufactured by using the semiconductor wafer for MT and the semiconductor wafer for HEMT
Regarding EMT.

[0002]

2. Description of the Related Art HEMT means an insulating substrate, a channel layer made of a non-doped semiconductor layer formed on the insulating substrate, and a semiconductor formed on the channel layer and forming the channel layer. A carrier supply layer made of a semiconductor layer containing an impurity having an electron affinity smaller than the electron affinity and having an n-type conductivity type, a control electrode provided on a part of the surface of the carrier supply layer, and the carrier supply described above. The other part of the surface of the layer has two electrodes provided in regions facing each other across the control electrode,
The thickness of the carrier supply layer is such that a depletion layer generated in a surface layer of the carrier supply layer and a depletion layer generated in a back layer of the carrier supply layer are connected to each other in a region facing the control electrode. A semiconductor device having a thickness such that the electric field effect of the control electrode extends to the interface between the carrier supply layer and the channel layer, wherein the electron affinity of the carrier supply layer and the electrons of the channel layer are The two-dimensional electron gas generated in the space near the interface between the carrier supply layer and the channel layer due to the difference in affinity is not affected by ionized impurity scattering, so that high electron mobility can be obtained especially at low temperature. A semiconductor device in which the above-mentioned two-dimensional electron gas having: is positively utilized as a current transmission medium.

In the planar-doped HEMT, the carrier supply layer is a laminated body including a planar-doped layer containing a high concentration of n-type impurities, and carrier supply is performed while preventing the movement of impurities to the channel layer. The two-dimensional electron gas has a high electron mobility because it has a function of supplying a sufficient amount of carriers to the space near the interface between the layer and the channel layer, and therefore the two-dimensional electron gas is less susceptible to ionized impurity scattering. Is obtained, and the switching speed is further improved in the HEMT.

FIG. 2 shows a layer structure of an example of a semiconductor wafer for planar-doped HEMT. In the figure, 1 is a semi-insulating GaAs substrate. 2 to 4 are buffer layers, and 2
4 to 300 are GaAs layers 2 and 5 having a thickness of 300 nm, respectively.
And Al _0.25 Ga _{0. 75} As layer 3 of 00nm thickness, a GaAs layer 4 Doo of 50nm thickness. Reference numeral 5 denotes a channel layer, which is a non-doped In _z Ga _1-z As layer having a thickness of 10 to 15 nm.
It is composed of layers (where z is 0.15 to 0.3). In principle, the impurities contained in the channel layer 5 are not problematic unless they are p-type having a high concentration so as to cancel the total amount of electrons supplied from the carrier supply layers 6, 7, and 8, but are generally undoped or low-doped. The concentration is n-type. 6 to 8 are carrier supply layers, and 6 to 8 are non-doped Al _x Ga _1-x As layers with a thickness of 3 nm (where x is 0.2 to 0.
3) Spacer layer 6 made of Si and 5 × 10 ¹² cm ⁻² of Si
A planar dope layer 7 formed by adsorbing
_Aly G having a thickness of 30 nm and containing n-type impurities at ¹⁷ cm ^-3
a _1-y As layer (where y is 0.2 to 0.3). 9 is an electrode forming layer, 4 × 10
GaA containing n-type impurities at ⁸ cm ^-3 or more and having a thickness of 50 nm
It consists of s layers. The reason why the electrode forming layer 9 has a high impurity concentration is to obtain low resistance.

Such a layered planar doped HE
There are two known methods for manufacturing a semiconductor wafer for MT, one of which is a method of using a metal organic chemical vapor deposition method on a surface slightly inclined from the (100) surface of a GaAs substrate.
The other is a method of forming the above layer structure, and the other is Ga
This is a method of forming the above layer structure on the (100) plane of an As substrate by using the molecular beam epitaxy method. The reason why the (100) plane cannot be used in the case of the metalorganic vapor phase epitaxy is that hillocks, which are unavoidable in the case of the (100) plane, must be prevented.

[0006]

The metal-organic vapor phase epitaxy method is superior in mass productivity to the molecular beam epitaxy method, but is planar-doped HE manufactured by using the metal-organic vapor phase epitaxy method.
The electron mobility of the two-dimensional electron gas generated in the MT semiconductor wafer is lower than the electron mobility of the two-dimensional electron gas generated in the planar-doped HEMT semiconductor wafer manufactured using the molecular beam epitaxy method.

In order to confirm this drawback, a pseudo-planar-doped HEMT semiconductor wafer having a layer structure shown in FIG.
It was manufactured by using both the metal organic chemical vapor deposition method and the molecular beam epitaxy method. In the figure, 1a is undoped G
aAs substrate. 2 to 4 are buffers, and each of 2 to 4 is a 300 nm thick GaAs layer 2 and 500 n
m _0.25 Ga _0.75 As layer 3 and 50 nm Ga
As layer 4. 5 is a channel layer and has a thickness of 1
It is a 5 nm non-doped In _0.18 Ga _0.82 As layer.
6.7.8 a is a carrier supply layer, and each of 6.7.8 a is a non-doped Al _x Ga _{1 -x} A layer with a thickness of 3 nm.
A spacer layer 6 made of an s layer (where x is 0.2 to 0.3), a planar doped layer 7 formed by adsorbing Si to 5 × 10 ¹² cm ⁻² , and a non-doped Al _y layer having a thickness of 30 nm.
And a cap layer 8a made of a Ga _1-y As layer (where y is 0.2 to 0.3). 9a is undoped GaAs
It is an electrode forming layer composed of layers. The reason why the layers other than the planar-doped layer 7 are non-doped layers is that the electron mobility and the electron concentration of the two-dimensional electron gas can be accurately measured.

These two types of pseudo-planar doped HE
The electron mobility and the electron concentration of the two-dimensional electron gas were measured at 77 K and room temperature using the MT semiconductor wafer. The measurement results are shown below.

[0009]

[Table 1] Measurement results at 77K Metalorganic vapor phase epitaxy Molecular beam epitaxy Electron mobility (cm ² / V · sec) 5,800 14,000 Electron concentration (10 ¹² cm ^-2 ) 2.9 2.8

[0010]

[Table 2] Measurement results at room temperature Metalorganic vapor phase epitaxy Molecular beam epitaxy Electron mobility (cm ² / V · sec) 3,200 5,600 Electron concentration (10 ¹² cm ^-2 ) 2.8 2.8 For each of the wafer manufactured using the metal organic chemical vapor deposition method and the wafer manufactured using the molecular beam epitaxy method, there is no significant difference in the electron concentration,
It is clear that the electron mobility is poor when manufactured using metalorganic vapor phase epitaxy.

By the way, since the metal organic chemical vapor deposition method is superior in mass productivity to the molecular beam epitaxy method, the metal organic chemical vapor deposition method is used to manufacture the metal organic chemical vapor deposition method. It would be extremely meaningful if a wafer comparable to the above-mentioned wafer could be manufactured.

An object of the present invention is to manufacture the organic metal vapor phase epitaxy method, which has excellent mass productivity, when the electron mobility of a two-dimensional electron gas is manufactured using the molecular beam epitaxy method. Planar-doped HEMT as high as
Another object of the present invention is to provide a semiconductor wafer for use in manufacturing, and to provide a planar doped HEMT manufactured by using the semiconductor wafer for use in planar doping HEMT.

[0013]

Among the above objects, the first object (a semiconductor for a planer-doped HEMT in which the electron mobility of a two-dimensional electron gas is high even when manufactured by using a metal organic chemical vapor deposition method) Wafer delivery)
In the semiconductor wafer for planar doped HEMT according to the present invention, a non-doped InGaAs layer forming a channel layer is formed on a surface slightly inclined from the (100) surface of a GaAs substrate via a buffer layer.
On the aAs layer, a non-doped Al _x Ga _1-x As layer that forms a spacer layer that is the first layer of the carrier supply layer is formed,
On the non-doped Al _x Ga _1-x As layer, a high-concentration n-type planar-doped layer that is the second layer of the carrier supply layer is formed, and on this planar-doped layer is the third layer of the carrier supply layer. In a semiconductor wafer for a planer-doped HEMT in which an Al _y Ga _1-y As layer forming a cap layer is formed, the Al mixed crystal ratio x of the non-doped Al _x Ga _1-x As layer is 0.4 or more, preferably Is 0.7 or more.

In order to achieve the second of the above objects (the provision of a planar-doped HEMT in which the electron mobility of a two-dimensional electron gas is high and the switching speed is further excellent), a planar-doped HEMT according to the present invention is provided. Is manufactured using the above-mentioned semiconductor wafer for planar-doped HEMT.

In the case of the semiconductor wafer for planar-doped HEMT manufactured by using the metalorganic vapor phase epitaxy method, in order to examine the reason why the electron mobility of the two-dimensional electron gas is low, a copy of the TEM photograph is shown in FIG. The semiconductor laminated body shown was manufactured.

It should be noted that in this TEM photograph copy, the step (GaA) is formed on the In _0.18 Ga _0.82 As layer.
There is a step bunching based on a slight inclination of the surface of the substrate 1a, and the thickness of the AlAs layer is uniform.

On the other hand, as shown in FIG. 5, i-In _0.18 G
If the upper layer of the a _0.82 As layer is not the AlAs layer but the Al mixed crystal ratio is lowered to 0.25 to form the Al _0.25 Ga _0.75 As layer, the thickness of the Al _0.25 Ga _0.75 As layer is not uniform. The result is a thick part and a thin part. Therefore,
In the structure of FIG. 3, it is estimated that the spacer layer 6 has a thick portion and a thin portion as in FIG. In the portion where the thickness of the Al _0.25 Ga _0.75 As layer is thin, the influence of ionized impurity scattering becomes large, and the electron mobility decreases.

Therefore, in FIG. 2, i-Al _x Ga is used.
_If the Al mixed crystal ratio x of the spacer layer 6 made of _1-x As layer is increased, the spacer layer 6 covers the channel layer 5 with a substantially uniform thickness, and the influence of ionized impurity scattering is reduced. be able to.

According to the results of the experiments described in the embodiments of the invention, the effect of the present invention was confirmed when the Al mixed crystal ratio x of the spacer layer 6 was larger than 0.4. x
When the value of is 0.7 or more, the effect of the present invention is extremely remarkable.

If the value of Al mixed crystal ratio x is large, AlGaAs
However, in the case of the semiconductor wafer for planar-doped HEMT according to the present invention, since the cap layer 8 and the electrode forming layer 9 are formed on the upper surface of the semiconductor wafer, the disadvantage that the spacer layer is easily oxidized is Will be complemented.

[0021]

In order to confirm the effect of the present invention, a plurality of semiconductor laminates having the same layer structure as the semiconductor wafer for pseudo-planar-doped HEMT whose layer structure is shown in FIG. The value of the crystal ratio y was fixed to 0.25, the value of the Al mixed crystal ratio x of the spacer layer 6 was changed from 0.25 to 1.00, and the organic metal vapor phase epitaxy method was used for the production. Then, the electron mobility and electron concentration of the two-dimensional electron gas generated in the space near the interface between the spacer layer 6 and the channel layer 5 were measured at 77K and room temperature. The measurement results are shown below.

[0022]

[Table 3] Measurement results at 77 K Electron mobility of spacer layer Electron concentration Al mixed crystal ratio x (cm ² / V · sec) (10 ¹² cm ^-2 ) 0.25 5,800 2.9 0.50 6, 600 2.9 0.60 9,200 2.8 0.70 12,000 2.8 0.80 12,500 3.0 1.00 12,600 2.9

[0023]

[Table 4] Measurement results at room temperature Electron mobility of spacer layer Electron concentration Al mixed crystal ratio x (cm ² / V · sec) (10 ¹² cm ^-2 ) 0.25 3,200 2.8 0.50 3, 700 2.9 0.60 4,100 2.9 0.70 5,000 2.8 0.80 5,200 2.9 1.00 5,000 2.9 The results are shown in a graph and shown in FIG. Shown in. It is recognized that the effect is recognized when the Al mixed crystal ratio x of the spacer layer is 0.4 or more, and the effect is remarkable when the value is 0.7 or more.

In particular, when the value of the Al mixed crystal ratio x of the spacer layer is 0.7 or more, the electron mobility of the two-dimensional electron gas is similar to that in the case of manufacturing using the molecular beam epitaxy method. Worth noting.

When a HEMT is manufactured by using this semiconductor wafer for planar-doped HEMT, since the electron mobility of the two-dimensional electron gas is excellent, the HMT of excellent performance is obtained.
It is clear that EMT can be manufactured.

[0026]

As described above, the spacer layer A of the semiconductor wafer for planar doped HEMT according to the present invention is
Since the value of the mixed crystal ratio x is 0.4 or more, preferably 0.7 or more, the electron mobility of the two-dimensional electron gas can be obtained even if the metal-organic vapor phase epitaxy method which is excellent in mass productivity is used. Is excellent, and the electron concentration is also high.

Further, the planar-doped HEM according to the present invention
Since T is manufactured using the above semiconductor wafer, it has an excellent switching speed.

[Brief description of drawings]

FIG. 1 is a graph showing the results of an effect confirmation test of the present invention.

FIG. 2 is a layer structure diagram of a semiconductor wafer for planar doped HEMT.

FIG. 3 is a layer structure diagram of a semiconductor wafer for pseudo-planar-doped HEMT manufactured to confirm the drawbacks solved by the present invention.

FIG. 4 is a copy diagram of a TEM photograph of a semiconductor laminate manufactured to study the reason why the electron mobility of a two-dimensional electron gas of a semiconductor wafer for planar-doped HEMT manufactured by using the metal organic chemical vapor deposition method is low. Is.

FIG. 5 is a copy diagram of a TEM photograph of a semiconductor laminate manufactured to study the reason why the electron mobility of a two-dimensional electron gas of a semiconductor wafer for planar-doped HEMT manufactured by using the metal organic chemical vapor deposition method is low. Is.

[Explanation of symbols]

1 semi-insulating GaAs substrate 2 GaAs layer forming a buffer layer 3 Al _0.25 Ga _0.75 As layer forming a buffer layer 4 GaAs layer forming a buffer layer 5 i-In _z Ga _1-z As layer forming a channel layer (however, z Is 0.15 to 0.3) 6 i-Al _x Ga _1-x As layer forming a spacer layer which is the first layer of the carrier supply layer (provided that x is 0.2 to 0.
3) 7 High-concentration n-type planar doped layer that is the second layer of the carrier supply layer 8 n-type AlyGa _1- yAs layer that forms the cap layer that is the third layer of the carrier supply layer (where y is 0. 2-0.
3) 9 Electrode forming layer 1a Non-doped GaAs substrate 8a Non-doped Aly Ga _1- y A forming a cap layer
s layer (where y is 0.2 to 0.3) 9a Electrode forming layer made of non-doped GaAs layer

Claims (3)

[Claims] 1. A non-doped InGa forming a channel layer on a surface slightly inclined from the (100) surface of a GaAs substrate.
As layer is formed via a buffer layer, undoped Al _x Ga _1-x As layer constituting the spacer layer is a first layer of the carrier supply layer on the undoped InGaAs layer is formed, the non-doped Al _x Ga _1-x as layer in a second layer of the carrier supply layer high concentration n-type planar doped layer is formed, Al _y forming the capping layer is a third layer of carrier supply layer on the planar-doped layer In a semiconductor wafer for planar-doped HEMT having a Ga _{1 -y} As layer formed thereon, the Al mixed crystal ratio x of the non-doped Al _x Ga _1-x As layer
Is 0.4 or more, and the planar dope H is characterized by
Semiconductor wafer for EMT. 2. A non-doped InGa forming a channel layer on a surface slightly inclined from the (100) surface of a GaAs substrate.
As layer is formed via a buffer layer, undoped Al _x Ga _1-x As layer constituting the spacer layer is a first layer of the carrier supply layer on the undoped InGaAs layer is formed, the non-doped Al _x Ga _1-x as layer in a second layer of the carrier supply layer high concentration n-type planar doped layer is formed, Al _y forming the capping layer is a third layer of carrier supply layer on the planar-doped layer In a semiconductor wafer for planar-doped HEMT having a Ga _{1 -y} As layer formed thereon, the Al mixed crystal ratio x of the non-doped Al _x Ga _1-x As layer
Is 0.7 or more, and the planar doped H is characterized by
Semiconductor wafer for EMT. 3. A planar-doped HEMT manufactured by using the semiconductor wafer for planar-doped HEMT according to claim 1 or 2.