JPS5893377A - Semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the electron surface density of a group of accumulated electrons and the level of electron mobility by a method wherein the device is subjected to electromagnetic wave irradiation at low temperatures after the formation of a channel layer on a substrate, electron-donative layer, alloyed layer and electrodes. CONSTITUTION:A channel layer 2 and electron-donative layer 3 are formed on a substrate 1, and alloyed layers 5 are formed by heat treatment, which extend through the electron-donative layer 3 to include the upper part of the channel layer 2. Next, source/drain electrodes 4 are formed on the alloyed layers 5, an ohmic contact is established with the channel layer 2, and a gate electrode 6 is formed. Then, exposure to electromagnetic waves represented by visible light is effected to result in the accumulation of a group of electrons 7 in the neighborhood of the hetero-boundary, which results in the constitution of a normal-ion type transistor with high electron mobility.

Description

DETAILED DESCRIPTION OF THE INVENTION +l) Technical Field of the Invention The present invention relates to a semiconductor device. For details, please refer to the earlier patent application filed by this patent application (Japanese Patent Application No. 55-8203).
5 and Japanese Patent Application No. 34-171026).

(2) Technical background High electron mobility transistors have different electron affinities2
A group of electrons (two-dimensional electron gas) accumulated near a single heterojunction surface formed by joining different semiconductors.
An active semiconductor device that controls the impedance of a conductive path formed by the group of accumulated electrons between a pair of other input/output electrodes by controlling the electron concentration of the electrode using a x-electrode.

A major feature of high electron mobility transistors is that the electron transferors of the above-mentioned accumulated electron group (two-dimensional electron gas) operate at low temperatures, e.g. In other words, the above-mentioned accumulated electron group (two-dimensional electron gas) becomes extremely large at temperatures of Since it is accumulated within a range of about <100X, it is spatially separated from the layer (electron supply layer) consisting of an early field with a small electron affinity, and its electron mobility is not affected by impurity scattering. Therefore, at low temperatures where the effect of impurity scattering combines with an increase in electron mobility, an extremely large electron transfer range exists, that is, at 77°K
．． 5 X 10'tym"/VB.

5 X 10'car'' / 'VS at 5°K
It has been experimentally confirmed that the

However, the electron mobility of such a group of accumulated electrons (two-dimensional electron gas) is more or less influenced by impurity scattering based on ionized impurities existing near the heterojunction. The impurity that causes this adverse effect is the electron Some substances are contained in the supply layer, that is, a semiconductor with a low electron affinity that forms the electron source, and others are contained in a semiconductor that has a large channel width, that is, a semiconductor that has a large electron affinity. In conventional high electron mobility transistors, the electron supply layer contains n-type impurities to serve as an electron source, and only the channel layer does not contain impurities. Therefore, in order to increase electron mobility by reducing the influence of scattering due to impurities contained in the early field with small electron affinity, it is necessary to increase the electron surface concentration of the accumulated electron group (two-dimensional electron gas). become.

Since the screening effect of the electron scattering potential increases due to the increase in electron surface concentration, in order to increase the electron surface concentration of the 0-accumulated electron group (two-dimensional electron gas), the n-type impurity concentration of the electron supply layer must be increased. It is sufficient to increase the electron mobility by increasing the electron mobility. However, on the other hand, if the n-type impurity concentration in the electron supply layer is increased, the concentration of n-type impurities diffused into the channel layer during high-temperature processes also increases, so the influence of impurity scattering based on the impurities present in this channel layer becomes large. As a result, electron mobility decreases. Therefore, it is impossible to increase the impurity concentration in the electron supply layer without limit! I can't.

(8) Conventional technology and problems High electron mobility transistors using conventional technology have the effect of increasing the electron surface concentration of accumulated electron groups (two-dimensional electron gas), but the amount of impurities that diffuse into the channel layer increases. For the purpose of preventing impurities, a layer ()? made of the same semiconductor as the electron supply layer and containing no impurities is placed between the electron supply layer containing n-type impurities and the channel layer containing no impurities. 77 layers) were interposed. By the way, if the thickness of this 9777 layer is increased, it is possible to prevent the impurity in the electron supply layer from diffusing into the channel layer, but on the other hand, the larger the thickness is, the more
Is it caused by a difference in electron affinity? Since the effect of the tensile gap is attenuated, the electron surface concentration of the accumulated electron group (two-dimensional electron gas) decreases.

In other words, the effect of 79277 layers naturally has a limit. However, if the electron source of the accumulated electron group (two-dimensional electron gas) is not the n-type impurity contained in the electron supply layer,
If other factors are satisfied, the effect of impurity scattering can be minimized and the electron surface concentration of the accumulated electron group (two-dimensional electron gas) can be made sufficiently large. It should be possible to make the electron mobility even larger than that of an electron mobility transistor.

(4) Object of the Invention The object of the present invention is to satisfy this requirement, and does not depend on the i-type impurity contained in the electron supply layer for the electron source, but requires this from other elements. , the electron mobility of the accumulated electron group (two-dimensional electron gas) is increased without increasing the influence of impurity scattering by sufficiently increasing the electron surface concentration of the accumulated electron group (two-dimensional electron gas). An object of the present invention is to provide an electron mobility transistor.

(+5) Structure of the Invention The structure of the present invention is as follows: (a) It has a double layer consisting of two types of fast field bodies having different electron affinities, and near the interface, the two types of fast field bodies have different electron affinities. A group of electrons (two-dimensional electron gas) accumulated based on the difference is used as a conductive medium, and (b) a control electrode formed on any of the layers of the above-mentioned fast field double layer is used to conduct input by the above-mentioned conductive medium. - In a high electron mobility transistor whose basic principle is to control the impedance of a conductive path configured between output electrodes, (c) both of the above two semiconductor layers do not substantially contain impurities. (b) Some or all areas of the control electrode are made to transmit electromagnetic waves such as light, and (b)
In the lower region of the control electrode, at least the electron supply layer is irradiated with electromagnetic waves at a low temperature, and is maintained at a low temperature.

In the above structure, not only the channel layer but also the electron supply layer does not contain impurities1, and the influence of impurity scattering is limited to a minimum. When the electromagnetic waves are irradiated to excite the fast field bodies that constitute the electron supply layer or the shallow impurity units contained therein, there is a sufficient amount of electron groups near the heterointerface between the electron supply layer and the channel layer. is accumulated to constitute a two-dimensional electron gas, so it is possible to provide a high electron mobility transistor in which the electron mobility is even higher than that in conventional high electron mobility transistors.

Note that in the above configuration (2), the surface concentration of the two-dimensional electron gas accumulated near the hetero interface between the electron supply layer and the channel layer is determined by the amount of free electrons generated by electromagnetic wave irradiation. , which is made of the same fast field material and contains n-type impurities, in contact with an electron supply layer that does not contain impurities and has a thickness that can be expected to be sufficiently effective in preventing the occurrence of the impurity scattering described above. The addition of additional layers is effective in increasing the electron transfer capacity.
! In this embodiment, the lower limit of the thickness of the electron supply layer that does not contain impurities is the thickness that can suppress the above-mentioned impurity diffusion.
aAa) and aluminum arsenic (mu/Ga mouth), about 150X &! be.

In the above structure, the amount of electrons accumulated in the vicinity of the hetero interface between the electron supply layer and the channel layer is maintained at a low temperature. In any case, it is inevitable that it will decrease exponentially over time.Therefore, 1. In addition to keeping the high electron mobility transistor in a low-temperature container, it is also intermittently irradiated with electromagnetic waves such as light. Providing a means, for example, a fast field light emitting element disposed opposite to the control electrode and a circuit to operate it at desired times, is extremely effective from the viewpoint of improving industrial applicability. This is significant because the lifetime of the high electron mobility transistor in this configuration is very long compared to the relatively short lifetime of the high electron mobility transistor in the first configuration. However, it is effective to provide an additional layer containing nll impurities.

Hatake:The two types of semiconductors that make up the electron mobility transistor must have (a) the same or similar lattice constants, (b) a large difference in electron affinity, and (c) TannP- Yatsude is thick %z! Although there are a large number of combinations, the present invention can be applied to any of the combinations.Also, high electron mobility transistors can be used in cases where the channel layer is configured as an upper layer of the electron supply layer. In some cases, the electron supply layer is formed as a lower layer, but the present invention can be applied to either of them. In general, materials with high electron affinity have a small Noman r gap and a long basic absorption edge wavelength, so the electron supply layer is a lower layer. In this case, the electrons irradiated to the electron supply layer are partially absorbed and attenuated in the channel layer, but especially when the channel layer is the upper layer, the thickness of the channel layer is extremely thin < 1000 It is desirable that the wavelength of the electromagnetic waves used for irradiation be shorter than the basic absorption edge wavelength of the semiconductor constituting the electron supply layer, but as mentioned above, there are Since the shallow impurity level of impurities contained in the It goes without saying that 0 (6) Embodiments are possible.Hereinafter, with reference to the drawings, two high electron mobility transistors according to embodiments of the invention included in this application will be explained, and the structure of the present invention and the structure of the present invention will be explained. Combinations of semiconductors, such as gallium arsenide (
Ga um θ) and aluminum gallium arsenic, 1. '.

(A/GaAs).

FIG. 1 shows a cross-sectional view of a high electron mobility transistor in a completed state according to a fresh example of the present invention.

In the figure, 1 is a substrate made of gallium arsenide (GaAs) containing chromium (Or), etc., and 2 is a substrate l.
Overlying the channel layer is a lattice-matched, superoxide, substantially impurity-free gallium arsenide (GaAs) layer having a thickness of approximately 0.05 mm. 3 is a lattice-matched top-oxide layer on the channel layer 2, which is substantially impurity-free aluminum, gallium arsenide (A/GaA
An electron supply layer 1 consisting of a layer s) and a semiconductor r@2.3 of 0 or more having a thickness of approximately 500 H is subsequently formed using a molecular beam epitaxial growth method. 4 is gold/germanium/gold (gold) selectively formed on the input/output electrode (source/drain electrode) formation region
- Input/output electrodes (source/output electrodes) made of auGe/Au) layers
Drain electrode) -7' is heat-treated at about 450°C to penetrate through the electron supply layer 3 and alloy to the upper part of the channel layer 2 to form an alloy layer 5. The electrode) 4 and the channel layer 2 are connected resistively. 6 is a control electrode (gate electrode) 'T
! In this example, it is an aluminum film having a thickness of about 100X. With such a thickness, electromagnetic waves such as light are transmitted, so an opening for light irradiation is unnecessary.

In the state after the completion of the above manufacturing process, no electron group is accumulated near the interface between the channel layer 2 and the electron supply layer 3, but when irradiated with electromagnetic waves such as light, the input/output electrodes (source and The electron group 7 is accumulated in the vicinity of the above-mentioned hetep interface, except for the lower region of the drain electrode), so that the transistor functions as a normally-on type high electron mobility transistor.

Here, the electron surface concentration of accumulated electrons* (two-dimensional electron gas) and its electron mobility in the state after electromagnetic wave irradiation are 770
The results measured at angles 1 and 5 degrees were as shown in the following table.

5°K LOX11 1,200,
000 This measurement result shows a significant improvement over the prior art values shown in the table below.

Electronic surface concentration and electron mobility in an example of conventional technology 770
K 13 x 10” 160,0
005'K &4 X 10" 5
4000 FIG. 2 shows a cross-sectional view of a completed high electron mobility transistor according to another embodiment of the present invention.

The difference from FIG. 1 is that the thickness of the electron supply layer 3 is somewhat thinner than 150 μm1, and that the electron supply layer 3 is made of n-type aluminum arsenide (mu/GaAs). The only difference is that there is an additional layer 8 of about 3150 A.

In this case, the accumulated electron group exists before being irradiated with electromagnetic waves such as light, but its value increases as shown in the table below by irradiation with electromagnetic waves from the party.

770K Electronic surface concentration CIL-” &!i
X 10111S, 0 X 10”electron mobility cm2
/Vwc 160,0QO-' 181LOO050
K Electronic surface concentration cm-” 3.4810”
5.7 X 10” electron mobility −/Vam s4G
, ooo 1.0I5a00G Furthermore, what is interesting is that when the irradiation amount of electromagnetic waves such as light is increased, as shown in Figure 3, the electron surface concentration increases as expected, but the electron mobility and electron It is not necessarily proportional to the surface concentration,
The relationship between the electron surface concentration and the electron mobility has a maximum value as shown in FIG. In the figure, the curve m is 77
Curve B shows the measurement results at 5 fins.

As mentioned above, since the electronic surface concentration decreases exponentially with time, the amount of irradiation of electromagnetic waves such as light may be determined by taking into account the characteristics shown in FIG.

(7) As described in detail, according to the present invention, the electron source does not depend on the njl impurity contained in the electron supply layer, but relies on other elements, and moreover, By increasing the electron surface concentration of the dimensional electron gas (2D electron gas) to a sufficiently high level, the electron mobility of the accumulated electron group (two-dimensional electron gas) is increased without increasing the influence of impurity scattering. degree transistor can provide 0

[Brief explanation of drawings]

FIG. 1 is a sectional view of a high electron mobility transistor according to one embodiment of the present invention, and FIG. 2 is a sectional view 1 of a high electron mobility transistor according to another embodiment of the present invention. FIG. 3 is a graph showing the relationship between the electron surface concentration and the irradiation amount when the electron supply layer of the high electron mobility transistor according to the present invention is irradiated with electromagnetic waves such as light, and FIG. 4 corresponds to FIG. This is a graph showing the relationship between electron mobility and electron surface concentration in the state of
...Channel layer (type 1 arsenide gallium crystal layer), 3...
・Electron supply layer (Type 1 Alkenniku Umgari 凰UM砒片 layer)
, 4... Input/output electrode (source/drain electrode), 5
... Alloying region of input and output electrodes, 6... Control electrode (
gate electrode), γ... accumulated electron group (two-dimensional electron gas)
, 8... Additional layer (n-type arginine layer), A... Curve showing electron mobility versus electron surface concentration measured at 77%, B... Electron measured at 58X Curve showing mobility versus electronic surface concentration. Figure 3 Illumination volume Attachment 4 Drawing density

Claims (4)

[Claims] (1) A layer made of semiconductor 1 and a layer made of another semiconductor having different electron affinities from each other, and the two semiconductors are separated based on the difference in electron affinity between the two semiconductors. Group of electrons accumulated near the interface of layers (two-dimensional electron gas)
is used as a conductive medium, and the impedance of a conductive path constituted by a skeleton conductive medium is controlled by a control electrode provided on either of the two semiconductor layers, and the conductive path is provided sandwiching the control electrode. In an active semiconductor device connected to a pair of input/output electrodes, the two semiconductor layers do not substantially contain impurities, and at least a portion of the control electrode transmits electromagnetic waves. It is possible to irradiate the lower region of the control electrode with electromagnetic waves, and after irradiating at least one of the two semiconductor layers with light at a low temperature, the two semiconductor layers are maintained at a low temperature. A semiconductor device characterized by: (2) Of the two substantially impurity-free semiconductors, a layer made of a semiconductor with a low electron affinity is in contact with a semiconductor made of the same semiconductor as the layer made of a semiconductor with a low electron affinity. 2. The semiconductor device according to claim 1, further comprising a layer containing type impurities. (3) It has a layer made of the semiconductor No. 1 and a layer made of another semiconductor having a different electron affinity value from the semiconductor No. 1, and the two semiconductors are separated based on the difference in electron affinity of the two semiconductors. Group of electrons accumulated near the interface of layers (two-dimensional electron gas)
is used as a conductive medium, the impedance of a conductive path constituted by the conductive medium is controlled by a control electrode provided on either of the two semiconductor layers, and the conductive path is provided with one conductive path sandwiching the control electrode. In the active medium conductor device, the two semiconductor layers are substantially free of impurities, and at least a partial region of the control electrode is connected to a pair of input/output electrodes. The active semiconductor device has a means for irradiating electromagnetic waves toward at least one of the two semiconductor layers in the lower region of the control electrode that has a smaller electron affinity, and the active semiconductor device is placed in a low temperature container. A semiconductor device characterized by being housed and maintained at a low temperature. (4) Of the two substantially impurity-free semiconductors, a layer made of a semiconductor with a low electron affinity is in contact with a semiconductor made of the same semiconductor as the layer made of a semiconductor with a low electron affinity. 4. The semiconductor device according to claim 3, further comprising a layer containing type impurities.