JPS6356960A - High-speed semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a high-speed semiconductor device having improved characteristics with low noise, by providing operating regions consisting of MOCVD semiconductor layers of III-V compounds formed on a {311}B substrate. CONSTITUTION:A semi-insulating single crystal GaAs substrate 1 has on princi pal surface 1a of {311}B, namely of {311}As. On that principal surface 1a, there are sequentially provided a first semiconductor layer 2 of undoped GaAs, a second semiconductor layer 3 of undoped AlxGa1-xAs (x=0.33), a third semicon ductor layer 4 of AlxGa1-xAs (x=0.33) doped with an n-type dopant Si and a fourth semiconductor layer 5 of a similarly doped n-type GaAs by controlling supply of a material gas by means of the continuous MOCVD. The material gas may be TMA, TMG or arsine AsH3 for example. An FET thus constructed has operating regions, namely semiconductor layers 2 and 3 in which a two- dimentional electronic gas layer 9 is formed, the semiconductor layers being formed by the MOCVD at a low V/III value around 30 for example. In this manner, the semiconductor layers are allowed to have a sufficiently low carrier concentration, whereby a residual impurity and deterioration of crystallinity due to such residual impurity can be avoided. Thus, a semiconductor device having high electron mobility and low noise can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to high-speed semiconductor devices, particularly HEMTs, 2DEG-FETs, TEG-FETs, etc., using m-v group compound semiconductors.
High electron mobility transistor or two-dimensional electron gas channel field effect transistor called FET etc.
It also relates to high-speed semiconductor devices such as MES-FETs, so-called Schottky gate field effect transistors.

[Summary of the invention]

The present invention is directed to organic total directional vapor phase growth, so-called M
OCVD (1'retalorganlc Chemi
A highly purified operating region is formed with less impurity contamination by the m-v group compound semiconductor layer produced by Cal VaporDeposits 1on), and improvements in high speed, low noise, etc. are achieved.

[Conventional technology]

Conventionally, high-speed semiconductor devices such as HEMT, 2DEG-F
E.T.

In TEG-PET or MES-FET, m-v group compounds such as A 1 xGal-xAs (0≦x<1) or InyGal-yAs (0≦y<1) have high electron mobility and are relatively crystalline. It is widely used because it is easy to form a semiconductor layer with excellent properties.

In this case, a GaAs single crystal substrate having a (10(1) crystal plane as a main surface) is used as a substrate on which the m-v group compound semiconductor is grown in a vapor phase. A configuration is adopted in which a GaAs-based or InGaAs-based m-v group compound semiconductor layer is epitaxially grown by, for example, MOCVD.

By the way, in the above-mentioned high-speed semiconductor device, the mixture of residual impurities such as carbon C and silicon Si is avoided in the m-v group compound semiconductor layer, which is the operating region, and the semiconductor layer has excellent crystallinity. This is required for its high speed and low noise. However, as mentioned above (1
00) For example, trimethylaluminum (CH
3) When forming an A I GaAs-based compound semiconductor layer by MOCVD using 3A lt as a raw material, the biggest drawback is carbon C contamination, which is a major drawback for improving characteristics such as higher speed and lower noise in high-speed semiconductor devices. It's a hindrance.

[Problem that the invention seeks to solve]

As described above, the present invention effectively avoids deterioration of characteristics due to residual impurities in high-speed semiconductor devices using m-v group compound semiconductors, and improves the performance of high-purity m-v group compound semiconductors. l0CVD
A high-speed semiconductor device is constructed using a vapor-phase grown semiconductor layer, and has high mobility and therefore excellent high speed performance, and low noise and therefore good characteristics.

That is, in the present invention, III-
It was discovered that the contamination of impurities in Group V vapor-grown semiconductors, and therefore the crystallinity, has a strong dependence on the crystal plane of the substrate, and the above-mentioned problems are solved by selecting the crystal plane orientation of the substrate.

Incidentally, the Journal of Crystal Growth (J
(Crystal Growth)
68. (1984) 148-156 etc. have also reported on the (100) crystal substrate and discussed the identification of the (111) A plane, but the present invention has obtained a different result. Based on these different results, a high-speed semiconductor device with excellent characteristics is provided.

[Means for solving problems]

In the present invention, the main surface is (311) B (that is, (
311) As the As plane), the operating region is a semiconductor layer formed on the (311)B substrate by organic total diagonal vapor phase growth (1'1OcVD) of an m-v group compound.

As is well known, MOCVD is a method for treating group ■ elements, A
For Ga, In, the organic metal gases trimethylaluminum (TMA), )limethylgallium (TMG), )limethylindium (T old)
, or triethylaluminum (TEA), I-
Ethyl gallium (TEG), ) ethyl indium (TEI), etc. are used, and for the group element Z As + P, its hydrides arsine ASH3 and phosphine circle 13 are used. Then, these are fed into the reaction vessel at a ratio of the Group 2 raw material to the Group 1 raw material (hereinafter referred to as the V1m ratio). In the reaction vessel, the above-mentioned (3
11) A B substrate is placed with a required substrate salinity Ts, and an m-v group compound semiconductor layer is epitaxially grown on the surface of the substrate by thermal decomposition of the above-mentioned source gas.

[Effect]

According to the above-described high-speed semiconductor device according to the present invention, carbon (C
) can be effectively avoided, and by selecting a small ratio of ■/■, donor impurities, that is, silicon (Si
), thereby making it possible to obtain a high-speed semiconductor device that has high carrier mobility and good crystallinity, and has excellent characteristics of high speed and low noise.

Figure 2 shows the measurement results of the carrier concentration, that is, the concentration of carbon C as an acceptor, and the mixed concentration of St as a donor when the V/nI ratio is changed. In this case, the substrate temperature Ts = 800' GaAs with C
This is a case in which measurements were performed on A Iio, 33Gao, and 87AS compound semiconductor layers formed on a substrate by MOCVD using trimethylaluminum, trimethylgallium, and arsine as source gases.

In the same figure, the mu mark is according to the present invention (311) B Ga
The above-mentioned A I GaAs MOC on an As single crystal substrate
Plotting the measurement results when forming a VD semiconductor layer shows n-type characteristics, and in this case, V/
Even when the III ratio was decreased, p-type was not exhibited. In addition, in the same figure, the marks O and . respectively indicate similar M on the conventional (100) GaAs substrate.
Indicates the carrier concentration relative to the V/I[[ ratio when a semiconductor layer is formed by OCVD, where ◯ indicates p-type characteristics, and ◯ indicates n-type characteristics. In addition, in the same figure, the marks and ■ marks are plots of the measurement results of carrier concentration with respect to the respective ■/■ ratios when a semiconductor layer was formed by similar MOCVD on a (311)A GaAs substrate. The mark indicates p-type, and the ■ mark indicates n-type.
When an m-v group semiconductor is formed on a substrate by MOCVD, it becomes p-type when the V/III ratio is made small. This is because carbon C enters the Ga site and acts as an acceptor. Furthermore, if the V1m ratio is increased, the amount of donors such as silicon St increases, and the carrier concentration increases. That is, as is clear from FIG. 2, as in the conventional example, (1
00) MOCVD semiconductor layer formed on the substrate, ■
/■ Inversion of p-type and n-type occurs when the ratio is around 80 to 120, whereas MOCV on the (311)B substrate according to the present invention
When the D semiconductor layer was formed, even if the V/■ ratio was made sufficiently low and the surface became cloudy, no reversal between p-type and n-type was observed, and the resistance was sufficiently high. Therefore, if the V1m ratio is selected to be a sufficiently small value, for example, 100 or less, the amount of both donor and acceptor impurities mixed in can be reduced, and a high-resistance semiconductor layer with a low carrier concentration can be configured as its operating region.

Moreover, Al x Ga on the (311)B substrate according to the present invention
Non-doped MOCVD of l-xAs (x=o, 33)
When a semiconductor layer is formed, and when a similar non-doped Al xGal-xAs (x=
FIGS. 3 and 4 show photoluminescence spectra at 4K when MOCVD semiconductor layers of 0.33) were formed. In these, V/I[I
= 135.

In FIGS. 3 and 4, the peak b on the right side, that is, on the long wavelength side, is due to the residual donor-carbon acceptor transition, and the peak a on the left side, that is, on the short wavelength side, is the half-width 6 where the carbon acceptor is bound to the residual donor. .516me V
This is the exciton peak of

In Figures 3 and 4, the left and right peaks a and b, that is, the exciton peak and the do+-- caused by residual impurities.
As is clear from the difference in relative intensity of the acceptor pair emission peaks, the MOCVD semiconductor layer formed on the (311)B substrate according to the present invention in FIG. 3 is different from that of the conventional (100)
It can be seen that this layer is less affected by residual carbon and has excellent crystallinity than a semiconductor layer formed on a substrate.

According to the research and consideration of the present inventors, carbon pollution is (
311)8 plane is the smallest, followed by (111) B.

It was confirmed that the contamination increased in order from (100), (111)A, and (311)A.

〔Example〕

The device of the present invention can be applied to various high-speed semiconductor devices such as FETs using two-dimensional carrier (electron, hole) gas channels, such as HEMT, 2DEG-FET, TEG-F.
Although the present invention can be applied to ET or various high-speed semiconductor devices such as MES-FHT, an example of the case where the present invention is applied to a two-dimensional electron gas channel type FET will be explained with reference to FIG. .

In the figure, (1) means that its main surface (1a) is (311)
B i.e. (311) As semi-insulating single crystal GaA
s substrate, on its main surface (1a), for example, 5000
A first semiconductor layer (2) made of undoped GaAs with a thickness of, for example, 100 mm;
A second semiconductor layer (3) made of xGal-xAs (x=o, :+3) and a third semiconductor layer (3) made of AlxGal-xAs (x=0.33) doped with n-type impurity Si. The semiconductor layer (4) and a fourth semiconductor layer (5) made of n-type GaAs are formed by continuous MOCVD by controlling the supply of raw material gas. In this case, the raw material gas is, for example, TMA or TMG.

and arsine AsHi. and the fourth semiconductor N
(5) is partially etched away to form a third semiconductor layer (4).
) is exposed to the outside and a gate, for example, a Schottky gate electrode (6) is deposited thereon, and the fourth semiconductor layer (5) left on both sides is covered with a source electrode (7) and a drain electrode (8), respectively. ) to form. With this configuration, a PET film in which a channel is formed by the two-dimensional electron gas layer (9) at the interface between the first semiconductor layer (2) and the second semiconductor layer (3).
is configured.

The FET with such a configuration has an operating region, that is, an undoped first region where a two-dimensional electron gas layer (9) is formed.
and the second semiconductor layers (2) and (3), as described above, with V/Iff of M at a small value close to about 30, for example.
By using an OCVD semiconductor layer, it is possible to construct a semiconductor layer with a sufficiently low carrier concentration as explained in Fig. 2, thereby avoiding residual impurities and deterioration of crystallinity due to these residual impurities, resulting in high electron mobility. A high-speed semiconductor device with good characteristics and low noise can be constructed.

Furthermore, in the above-mentioned example, the explanation was mainly made of the AlxGal-xAs based compound as the ■-■ group compound, but it can also be applied to a high-speed semiconductor device using an InyGaly-yAs based MOCVD semiconductor layer.

Further, the present invention is applicable not only to the above-mentioned example but also to various high-speed semiconductor devices, such as A I Ga
It can also be applied to the so-called reverse 11E elbow in which a GaAs layer is formed on As, and in this case, the problem of crystallinity of the underlying Aβ-containing A I GaAs layer has been solved, so that Since the characteristics of GaAs are also improved, it becomes possible to form a channel using a two-electron gas layer with higher mobility.

Furthermore, characteristics can be similarly improved not only in FETs using a two-dimensional electron gas layer but also in FETs using a two-dimensional hole gas layer.

〔Effect of the invention〕

As described above, according to the high-speed semiconductor device according to the present invention,
Carrier mobility, or high speed, can be increased,
Furthermore, since a high-speed semiconductor device is constructed with an operating region having excellent crystallinity, an excellent high-speed semiconductor device with excellent high-speed performance and low noise characteristics can be obtained, and its practical benefits are extremely large.

[Brief explanation of drawings]

FIG. 1 is a line cross-sectional view of an example of the device of the present invention, FIG. 2 is a curve diagram showing the measurement results of the relationship between V/I ratio and carrier concentration, and FIG. Figure 4 shows MOCVD on (311)B substrate and (100) substrate, respectively.
FIG. 3 is a photoluminescence spectrum diagram of a semiconductor layer formed using the above method. (11 is a substrate, (2) to (5) are first to fourth semiconductor layers.

Claims (1)

[Claims] {311}B A high-speed semiconductor device comprising an operating region made of a metal organic vapor phase grown semiconductor layer of a III-V compound formed on a substrate.