JP3792057B2 - Heterojunction bipolar transistor and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heterojunction bipolar transistor made of a compound semiconductor material and a manufacturing method thereof, and more particularly to an npn heterojunction bipolar transistor.
[0002]
[Prior art]
In recent years, crystal growth of GaAs heterojunction bipolar transistors composed of compound semiconductors has become easier, so research and development aimed at the practical application of semiconductor devices used at high frequencies such as heterojunction bipolar transistors have been actively conducted. ing. In order to improve the high frequency characteristics of such a semiconductor device, it is necessary to achieve both a lower base resistance Rb and a higher current gain β. The base resistance Rb can be considered to have three components: an intrinsic base resistance, an external base resistance, and a base electrode / base interlayer contact resistance. However, the intrinsic base resistance is generally much smaller than the other two components and is generally negligible.
[0003]
On the other hand, in order to achieve a high current amplification factor β, it is necessary to reduce the thickness of the base layer or lower the carrier concentration of the base layer, both of which are base resistance components (external base resistance and base electrode / base Interlayer contact resistance) is increased. This shows that it is difficult to achieve both a high current gain β and a lower base resistance Rb.
[0004]
For this reason, as shown in Japanese Patent Laid-Open No. 5-326545, the prior art has required selective growth of the external base layer in order to improve the high frequency characteristics. This conventional example will be described with reference to FIG. FIG. 8 shows a conventional semiconductor device. In this conventional example, an n-type GaAs collector buffer layer 101, a GaAs collector layer 102, a C-doped p-type GaAs base layer 103, an n-type Al layer are formed on a semi-insulating GaAs substrate 110._0.3Ga_0.7An As emitter layer 104 and an n-type InGaAs emitter cap layer 105 are epitaxially grown sequentially. Next, this is processed into a mesa shape, and after selectively forming a C-doped p-type GaAs external base layer 106 by an appropriate growth method, an emitter electrode 107, a base electrode 108, and a collector electrode 109 are formed. In this conventional example, in order to obtain higher high frequency characteristics, a C-doped p-type GaAs external base layer 106 is selectively formed to achieve both a low base resistance Rb and a high current gain β.
[0005]
[Problems to be solved by the invention]
However, as disclosed in Japanese Patent Laid-Open No. 5-326545, the conventional technique generally uses a base layer with a carrier concentration of 2 × 10 in order to achieve a high current gain β.¹⁹cm^-3) Must be set to a lower value. Therefore, since the high-resistance C-doped p-type GaAs base layer 103 is formed, the base electrode / base interlayer contact resistance is eventually reduced, but the external base resistance component remains high, and effective high-frequency characteristics are improved. I couldn't see it. Therefore, the reduction of the base resistance component is to reduce the external base resistance in conjunction with the reduction of the base electrode / base interlayer contact resistance, and it is necessary to achieve both the reduction of the base electrode / base interlayer contact resistance and the reduction of the external base resistance. Is considered to give good high frequency characteristics.
[0006]
For this reason, it is an important issue to realize a C-doped GaAs base layer that can be handled as if the base electrode / base interlayer contact resistance value, the external base resistance value, and the current amplification factor can be set independently. It is considered that overcoming this problem is useful for improving the high-frequency characteristics of the heterojunction bipolar transistor.
[0007]
[Means for Solving the Problems]
  C-doped Al of claim 1 of the present invention_xGa_1-xAs (0 ≦ x ≦ 0.2)Including a layer consisting ofIn a heterojunction bipolar transistor having a base layer,The base layer includes an inner base layer formed immediately above the emitter layer and an outer base layer extending from the inner base layer to the outside of the region where the emitter layer is formed. The H concentration is higher than the C—H concentration in the outer base layer, andThe heterojunction bipolar transistor is characterized in that the current amplification factor β is increased and stabilized by performing initial energization with transistor operation. Specifically, the electron trap caused by the C—H bond that captured the electrons by the initial energization suppresses recombination by other traps in the base layer, the base current is reduced, and as a result, the current amplification factor β is improved. To do.
[0008]
A second aspect of the present invention provides a current amplification factor β before the initial energization.₀In contrast, the rate of increase of the current amplification factor β after initial energization (β / β₀) Is 110% or more.
[0009]
According to a third aspect of the present invention, an energization current amount during the initial energization is at least 1 kA / cm.²It is the above.
[0010]
The C-doped Al according to claim 4 of the present invention_xGa_1-xThe C—H concentration in the As (0 ≦ x ≦ 0.2) base layer is 10% or more of the C concentration. The electron trap resulting from this C—H bond contributes to the improvement of the current amplification factor.
[0011]
The heterojunction bipolar transistor according to claim 5 of the present invention is the C-doped Al_xGa_1-xThe carrier concentration of the As (0 ≦ x ≦ 0.2) base layer is 1.4 × 10¹⁹cm^-3To 6.5 × 10¹⁹cm^-3It is desirable to be in the range.
[0012]
  C-doped Al according to claim 6 of the present invention_xGa_1-xAs (0 ≦ x ≦ 0.2)Including a layer consisting ofA method of manufacturing a heterojunction bipolar transistor having a base layer includes:_xGa_1-xAs (0 ≦ x ≦ 0.2)Layer consisting ofincludingBecome the base layerLaminated III-V compound semiconductor layer structureAnd a process of III In order to have a region where the surface of the group V compound semiconductor layer structure is exposed, III Forming an emitter layer on the -V group compound semiconductor layer structure; III Forming a base electrode in a region where the surface is exposed in the group V compound semiconductor layer structure, and forming an emitter layerAfter, base electrodeTheFormationDoBefore the heat treatment processBy III The C—H concentration of the external base layer located in the region where the surface is exposed in the group V compound semiconductor layer structure is made lower than the C—H concentration of the internal base layer located immediately below the emitter layer.And transistor operationTheIt is characterized in that initial energization is performed. As a result, the transistor exhibits stable high frequency characteristics.
[0013]
Our experimental results show that C-doped GaAs layer and C-doped Al_xGa_1-xThe As (0 ≦ x ≦ 0.2) layer is crystallographically equivalent and has a high Al—C bond energy. Therefore, the higher the Al mixed crystal ratio, the higher the growth temperature, the V group gas, and the III group. Although there was a difference in the characteristics in which the carrier concentration increased with respect to the gas flow ratio, the GaAs layer and the C-doped Al_xGa_1-xThe same effect was obtained with the As (0 ≦ x ≦ 0.2) layer.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
(Example 1)
FIG. 1 shows Al according to an embodiment of the present invention._yGa_1-yAs / Al_xGa_1-xIt is sectional drawing which shows an As type | system | group heterojunction bipolar transistor. Specifically, an n-type GaAs collector buffer layer 1 (thickness 500 nm), a GaAs collector layer 2 (thickness 700 nm), an internal C-doped p-type Al layer are formed on a semi-insulating GaAs substrate 10 by MOCVD._xGa_1-xAs base layer 3 (thickness 50 nm) is laminated. Internal C-doped p-type Al_xGa_1-xThe As base layer 3 has a simple gradient structure in which the mixed crystal ratio x = 0.2 on the emitter side and x = 0 on the collector side. This is intended to accelerate the electrons at a higher speed by generating an internal electric field in the base layer and improve the current gain. N-type Al_yGa_1-yAn As emitter layer 4 (y = 0.3, thickness 200 nm) and an n-type InGaAs layer emitter cap layer 5 (thickness 100 nm) are epitaxially grown sequentially.
[0016]
C-doped p-type Al_xGa_1-xThe growth conditions for growing the As base layer 3 are a growth temperature of 450 ° C. to 650 ° C. and a V / III group gas flow ratio of 2.0 to 7.5. Where C-doped p-type Al_xGa_1-xWhen the As base layer 3 is epitaxially grown by the MOCVD apparatus (TMGa (trimethyl gallium) -TMAs (trimethyl arsenic)), the growth temperature and the ratio of the group V gas to the group III gas should be lowered to such an extent that the surface morphology does not deteriorate. The ratio of the C—H concentration to the C concentration can be increased. In Example 1, a growth temperature of 500 ° C. and a V / III group gas flow ratio of 3.0 were adopted. When the growth temperature of this example is 500 ° C. and the V / III flow rate ratio is 3.0, the C concentration is 4 × 10 according to SIMS analysis.¹⁹cm^-3The CH concentration was 12 × 10¹⁹cm^-3Met.
[0017]
After growing the above layers, etching is performed twice until the base layer 3 is exposed leaving the emitter layer and until the collector layer 2 is exposed leaving the emitter and base layers, and this is processed into a mesa shape. Then, for example, SiN_xA protective film is formed on the surface, and N₂Low resistance external C-doped p-type Al after heat treatment at 400 ° C for 5 minutes in atmosphere_xGa_1-xAs base layer 6 is formed. Protective film is SiN_xNot limited to SiO₂Etc. Further, the heat treatment temperature and time are not limited to the above conditions. It may also be before processing into a mesa mold that exposes the collector. By this heat treatment, low resistance external C-doped p-type Al_xGa_1-xThe sheet resistance of the As base layer 6 was 200Ω / □, which was about 1/3 of the resistance value of 600Ω / □ when no heat treatment was performed. Thereafter, the protective film is removed, and an emitter electrode 7, a base electrode 8, and a collector electrode 9 are formed. After forming a semiconductor device composed of a GaAs heterojunction bipolar as described above, each electrode is 1 kA / cm with a prober needle.²Are injected from the emitter to operate the transistor.
[0018]
Next, referring to FIGS. 3 to 6, a C-doped p-type Al containing a large amount of C—H bonds produced as described above._xGa_1-xThe operation of the heterojunction bipolar transistor having the As (0 ≦ x ≦ 0.2) base layer exhibiting a high current amplification factor will be briefly described.
[0019]
3 to 6 show C-doped p-type Al containing a large amount of C—H._xGa_1-xFIG. 6 is an energy band diagram of a heterojunction bipolar transistor using an As (0 ≦ x ≦ 0.2) layer as a base layer. ○ represents an electron, and → schematically represents the direction of electron diffusion during transistor operation. ☆ schematically shows an electron trap that does not capture electrons among the electron traps attributed to the C—H bond, and ● indicates schematically one that captures electrons among the electron traps attributed to the C—H bond. □ indicates other traps due to lattice defects and other impurities.
[0020]
FIG. 3 shows a C-doped p-type Al containing a large amount of C—H._xGa_1-xA schematic energy band diagram of a heterojunction bipolar transistor having an As (0.ltoreq.x.ltoreq.0.2) layer as a base layer before initial energization accompanying transistor operation is shown.
[0021]
C-doped p-type Al epitaxially grown at a growth temperature as low as 450 to 690 ° C. by MOCVD and a V / III group gas flow ratio of 5.0 or less_xGa_1-xAs shown in FIG. 3, the As (0 ≦ x ≦ 0.2) base layer has an electron trap due to C—H bonding (indicated by ☆) in the forbidden band of the base layer of the heterojunction bipolar transistor. At the same time, as indicated by □ above the Fermi level and below the conduction band, there are other traps caused by impurities such as lattice defects and heavy metals inherent to the material.
[0022]
FIG. 4 shows a C-doped p-type Al containing a large amount of C—H._xGa_1-xAn energy band diagram of an initial state in which a current amplification factor is increased, particularly during initial energization accompanied by transistor operation in a heterojunction bipolar transistor having an As (0 ≦ x ≦ 0.2) layer as a base layer is shown.
[0023]
As shown in FIG. 4, at the beginning of initial energization with transistor operation, electrons are injected from the emitter layer into the base layer, and an electron trap due to C—H coupling captures the electrons (indicated by →). The electron trap due to the C—H bond that has captured this electron continues to exist stably, and the trap that has captured this electron is considered to suppress electron-hole recombination via other traps in the base layer. . As a result, the base current due to recombination by the trap is reduced, and as a result, the current amplification factor is increased.
[0024]
FIG. 5 shows a C-doped p-type Al containing a large amount of C—H._xGa_1-xThe energy band during the transistor operation of the heterojunction bipolar transistor using the As (0 ≦ x ≦ 0.2) layer as a base layer, particularly in a state where the increase in current gain is saturated, and therefore immediately before the end of initial energization. The figure is shown.
[0025]
As shown in FIG. 5, the electrons injected into the base layer are trapped in the electron trap and become stable. In our experimental results, the energy required to emit electrons from this trap was about 2 eV. For this reason, electrons continue to be trapped in the trap and exist stably even after the end of the initial energization. For this reason, electrons flow through the conduction band. However, since the number of traps is finite, the decrease in the recombination base current value is saturated when electrons are trapped in all traps. At the same time, saturation of suppression of the recombination current through other traps inherent to the material also occurs, resulting in saturation of the increase in current gain.
[0026]
FIG. 6 shows a C-doped p-type Al containing a large amount of C—H._xGa_1-xThe energy band figure after the initial electricity supply of the heterojunction bipolar transistor which made an As (0 <= x <= 0.2) layer a base layer was completed is shown.
[0027]
As shown in FIG. 6, the electrons once trapped in the trap continue to be trapped in the trap after electrons are no longer injected from the emitter (even when the transistor is not operating), and show stable voltage-current characteristics. become. As a result, the heterojunction bipolar transistor of the present invention suppresses recombination caused by traps that have captured electrons due to other traps in the base layer, so that the base carrier concentration and the base layer thickness are the same and the C—H concentration is the same. Compared with a heterojunction bipolar transistor having a small base layer, a high current amplification factor can be realized. The energization amount at the initial energization is 1 kA / cm²The above is effective to bring about the above effect.
[0028]
Next, C-doped p-type Al containing a large amount of C—H bonds_xGa_1-xThe operation of the heterojunction bipolar transistor having the As (0 ≦ x ≦ 0.2) base layer exhibiting a low external base resistance will be briefly described.
[0029]
As explained above, C-doped p-type Al containing a large amount of C—H bonds_xGa_1-xBy applying heat treatment and initial energization treatment to the heterojunction bipolar transistor having an As (0 ≦ x ≦ 0.2) base layer, a high current amplification factor can be maintained even if the base carrier concentration is increased. On the other hand, since there are many C—H bonds, more carbon is activated by cutting the C—H bonds, so that the carrier concentration can be increased and it is easy to realize a low external base resistance. is there.
[0030]
That is, by providing an insulating layer having a thickness of 50 nm or less on the base layer and performing a heat treatment at about 400 ° C., the C—H bond can be easily disconnected to release hydrogen into the atmosphere and activate carbon. As a result, the carrier concentration of the external base layer can be easily increased by setting the insulator layer formed on the external base layer to 50 nm or less.
[0031]
In the present invention, the semiconductor multilayer film formed by the MOCVD epitaxial growth method is subjected to mesa processing, and then heat treatment is applied to the base layer portion exposed from the emitter layer before forming the base electrode, whereby low resistance external C-doped p-type Al._xGa_1-xThe C—H bond contained in the As (0 ≦ x ≦ 0.2) base layer is cut by heat treatment, hydrogen is expelled to the outside of the semiconductor layer, carbon is activated, and the carrier concentration can be increased. . With the external base layer having a high concentration, a low base resistance can be realized, and good high frequency characteristics can be given to the semiconductor device.
[0032]
In this method, when there is a thick semiconductor layer (about 50 nm or more) on the upper layer of the base layer, H cannot be expelled from the semiconductor layer. Therefore, the C-doped p-type Al in which the emitter layer is formed on the upper layer._xGa_1-xIt cannot be applied to an As (0 ≦ x ≦ 0.2) base layer portion.
[0033]
C-doped p-type Al by MOCVD epitaxial growth_xGa_1-xIn order to contain a large amount of C—H in the As (0 ≦ x ≦ 0.2) base layer, it is necessary to completely decompose TMGa (trimethylgallium) and not to make Ga atoms alone. In TMGa, C—H is Ga—CH._ThreeAl-CH_ThreeIt is known that gas is supplied in the form of For this reason, it is better to make the growth temperature as low as possible. However, when the growth temperature is low, the decomposition of the group V source gas is generally insufficient, which deteriorates the morphology of the growth layer surface. Therefore, it is generally necessary to increase the V / III ratio of the raw material gas. C-doped p-type Al epitaxially grown under these conditions_xGa_1-xThe As (0 ≦ x ≦ 0.2) base layer can contain a large amount of C—H bonds.
[0034]
The heterojunction bipolar transistor of the present invention is a C-doped Al_xGa_1-xWhen the CH concentration in the As (0 ≦ x ≦ 0.2) base layer is 10% or more with respect to the C concentration, an increase in the current amplification factor β after the initial energization can be confirmed, and the current amplification factor β increases and is stable. To do.
[0035]
In addition, the current amplification factor β before the initial energization₀The increase rate of current amplification factor β after initial energization (β / β₀) Is 110% or more, it is effective for the reduction of the external base resistance and the high frequency characteristics such as the maximum oscillation frequency with respect to the current amplification factor.
[0036]
C-doped Al_xGa_1-xWhen an As (0 ≦ x ≦ 0.2) base layer is grown using an organic metal containing a C—H bond as a raw material, it is not necessary to create a C—H bond, so there is no need to add a special device to the growth apparatus. It is advantageous on the initial investment of equipment.
[0037]
C-doped Al by metalorganic vapor phase epitaxy_xGa_1-xWhen growing an As base layer, TMGa and AsH_ThreeIs used as the raw material, the C—H concentration can be made higher than the C concentration, the external base resistance can be reduced with respect to the current amplification factor, and a high current amplification factor β can be maintained.
[0038]
C-doped Al by metalorganic vapor phase epitaxy_xGa_1-xWhen growing an As (0 ≦ x ≦ 0.2) base layer, C-doped Al_xGa_1-xWhen As (0 ≦ x ≦ 0.2) base layer is made of TMGa and TMAs, TMGa and AsH_ThreeThe C—H concentration can be made higher than when using the above, the external base resistance can be further reduced, and a high current gain β can be maintained.
[0039]
C-doped Al by metalorganic vapor phase epitaxy_xGa_1-xWhen growing an As (0 ≦ x ≦ 0.2) base layer, C-doped Al_xGa_1-xAs (0 ≦ x ≦ 0.2) base layer is CBr_FourWhen (carbon tetrabromide) is used as the doping material, the external base resistance is similarly reduced, and the degree of freedom is higher and the C-doped Al_xGa_1-xIt was found that the carrier concentration of the As (0 ≦ x ≦ 0.2) base layer can be set, which is advantageous.
[0040]
When the above growth material is used, C-doped Al_xGa_1-xThe carrier concentration of the As (0 ≦ x ≦ 0.2) base layer is 1.4 × 10¹⁹cm^-3To 6.5 × 10¹⁹cm^-3An increase in the current amplification factor β is observed in the range, and the C—H concentration can be increased.
[0041]
C-doped Al grown under the above conditions_xGa_1-xA heterojunction bipolar transistor including an As (0 ≦ x ≦ 0.2) base layer can realize a low external base resistance by including a heat treatment step in the manufacturing process before the formation of the base electrode after mesa processing. Shows high frequency characteristics.
[0042]
As described above, electrons are captured in the electron trap caused by C—H by continuous initial energization, the trap is neutralized, the recombination current component of the base current is reduced, and all traps are neutralized. When stabilized, a high current amplification factor β is achieved as a result. For example, FIG. 7 shows a Gummel plot of the state before the initial energization and the stable state after the transistor operation initial energization in the grounded emitter so that the decrease in the base current can be easily understood. A thin line indicates a state before initial energization, and a thick line indicates a stable state after initial operation of the transistor. As can be seen from the figure, the base current is decreased by 60 seconds of continuous initial energization, the collector current is increased accordingly, and the current amplification factor β is increased. The collector current increases after 60 seconds of energization than before initial energization, but since the vertical axis is a logarithmic axis, the thin line before initial energization overlaps with the thick line after 60 seconds of energization.
[0043]
Also, the current gain before initial energization is expressed as β₀And β is the stable current amplification factor after continuous initial energization, and the increase rate of the current amplification factor is (β) / (β₀), (C−H concentration) / (C concentration) was found to be proportional to the current amplification factor. Also, the rate of increase in current gain (β) / (β₀) Is 110% or more, maximum oscillation frequency f_maxAlso improved.
[0044]
Also in the high frequency characteristics, in the embodiment, the maximum oscillation frequency f_max= 234 GHz. On the other hand, when the low resistance external C-doped p-type GaAs base layer 6 is not formed without heat treatment, the maximum oscillation frequency f_max= 203 GHz. In a heterojunction bipolar transistor in which the normal C—H concentration of the same base sheet resistance is 10% or less of the C concentration, the maximum oscillation frequency f_max= 121 GHz, it can be seen that the heterojunction bipolar transistor of this example has good high frequency characteristics.
[0045]
Example is Al_yGa_1-yAs / Al_xGa_1-xAlthough the explanation has been made by using the As-based heterojunction bipolar transistor as an example, the same effect can be obtained even in the InGaP-based regardless of the semiconductor material of the emitter.
[0046]
(Example 2)
FIG. 2 is a cross-sectional view showing an InGaP / AlGaAs heterojunction bipolar transistor according to an embodiment of the present invention. That is, an n-type GaAs collector buffer layer 21 (thickness 500 nm), a GaAs collector layer 22 (thickness 700 nm), a C-doped p-type Al layer are formed on a semi-insulating GaAs substrate 20 by MOCVD._0.2Ga_0.8As base layer 23 (thickness 50 nm), n-type In_0.5Ga_0.5A P emitter layer 24 (thickness 200 nm) and an n-type InGaAs layer emitter cap layer 25 (thickness 100 nm) are epitaxially grown sequentially.
[0047]
Internal C-doped p-type Al of the present invention_0.2Ga_0.8The growth conditions for the As base layer 23 were a growth temperature of 450 ° C. to 680 ° C. and a V / III group gas flow ratio of 20 to 430. Where internal C-doped p-type Al_0.2Ga_0.8The As base layer 23 is formed by a MOCVD apparatus (TMGa-AsH_Three-CBr_Four), The ratio of the C—H concentration to the C concentration can be increased by reducing the growth temperature and the ratio of the group V gas flow rate to the group III gas to such an extent that the surface morphology does not deteriorate. . In Example 2, a growth temperature of 600 ° C. and a V / III gas flow ratio of 80.0 were employed. The growth temperature is 600 ° C., the V / III flow rate ratio is 80.0, and CBr_FourWhen the flow rate is 40 SCCM, according to SIMS analysis, the C concentration is 5 × 10¹⁹cm^-3The CH concentration was 2 × 10¹⁹cm^-3Met.
[0048]
CBr_FourIs used as a doping gas, the doping concentration does not depend on the V / III gas flow ratio, and CBr_FourSince the doping concentration can be set independently depending on the flow rate, it is more advantageous to implement this embodiment.
[0049]
After growth, this is processed into a mesa shape. Then, a suitable protective film such as SiN_xOn the surface, N₂Low resistance external C-doped p-type Al after heat treatment at 400 ° C for 5 minutes in atmosphere_0.2Ga_0.8An As base layer 26 is formed. By this treatment, low resistance external C-doped p-type Al_0.2Ga_0.8The sheet resistance of the As base layer 26 was 180Ω / □, which was about 80% of the resistance value of 220Ω / □ when heat treatment was not performed. Also in this case, the protective film is SiN._xNot limited to SiO₂Etc. The heat treatment temperature and time are not limited to the above conditions. Further, after that, the protective film is removed, and an emitter electrode 27, a base electrode 28, and a collector electrode 29 are formed.
[0050]
After forming the semiconductor device, each electrode is energized with a prober needle to operate as a transistor. By continuously energizing, the base current decreases and stabilizes, and as a result, the same high current amplification factor β as in the first embodiment is achieved.
[0051]
Also in this example, as in Example 1, the current amplification factor before the initial energization is expressed by β₀And β is the current amplification factor after the stable initial energization after continuous energization, and the increase rate of the current amplification factor is (β) / (β₀) Is proportional to (C−H concentration) / (C concentration). Increase rate of current gain (β) / (β₀) Is 110% or more, maximum oscillation frequency f_maxWill also improve.
[0052]
Also in the high frequency characteristic, in this embodiment, the maximum oscillation frequency f_max= 291 GHz. Instead of the InGaP emitter layer of this embodiment of the reference, an AlGaAs emitter layer is adopted, and a C-doped p-type In_0.2Ga_0.8Maximum oscillation frequency f of heterojunction bipolar transistor when As base layer 26 is formed_maxIn view of the fact that = 251 GHz, this example also has good high-frequency characteristics.
[0053]
In this example, InGaP / Al_xGa_1-xAn example is an As-based heterojunction bipolar transistor._yGa_1-yAs / Al_xGa_{1 -x}Maximum oscillation frequency f compared with As heterojunction bipolar transistor_maxIt was found that the improvement was remarkable. This is because when a large amount of C—H is contained in the base layer, Al_xGa_1-xIt has been found that an InGaP emitter layer is more advantageous than an As emitter layer. This is considered to be an effect that the InGaP emitter layer more effectively confines C—H in the base layer.
[0054]
【The invention's effect】
As described above, according to the present invention, when the epitaxial growth is performed by the MOCVD apparatus, the C— Increase the H concentration ratio. When this becomes a heterojunction bipolar transistor element and operates as a transistor, the rate of increase in current gain (β) / (β₀). As a result, a high current amplification factor β is obtained, and good high frequency characteristics are given. In addition, low resistance external C-doped p-type Al_xGa_1-xBy forming the As (0 ≦ x ≦ 0.2) base layer, better high frequency characteristics can be provided.
[Brief description of the drawings]
FIG. 1 shows Al according to Example 1 of the present invention._yGa_1-yAs / Al_xGa_1-xIt is sectional drawing which shows an As type | system | group heterojunction bipolar transistor.
FIG. 2 is a cross-sectional view showing a GaInP / GaAs heterojunction bipolar transistor according to Example 2 of the present invention.
FIG. 3 shows Al according to the present invention._yGa_1-yAs / Al_xGa_1-xIt is a simple energy band figure before the initial stage electricity supply of an As type | system | group heterojunction bipolar transistor.
FIG. 4 shows Al according to the present invention._yGa_1-yAs / Al_xGa_1-xFIG. 4 is a simple energy band diagram during initial energization of an As-based heterojunction bipolar transistor.
FIG. 5 shows Al according to the present invention._yGa_1-yAs / Al_xGa_1-xIt is a simple energy band diagram in which initial energization of an As-based heterojunction bipolar transistor is almost saturated.
FIG. 6 shows Al according to the present invention._yGa_1-yAs / Al_xGa_1-xIt is a simple energy band figure after electricity supply of an As type heterojunction bipolar transistor.
FIG. 7 shows Al according to an embodiment of the present invention._yGa_1-yAs / Al_xGa_1-xFIG. 6 is a Gummel plot diagram of an As-based heterojunction bipolar transistor at the grounded emitter.
FIG. 8 is a cross-sectional view showing a conventional AlGaAs / GaAs heterojunction bipolar transistor.
[Explanation of symbols]
1 n-type GaAs collector buffer layer
2 GaAs collector layer
3 Internal C-doped p-type Al_xGa_1-xAs base layer
4 n-type Al_0.3Ga_0.7As emitter layer
5 n-type InGaAs emitter cap layer
6 Low resistance external C-doped p-type Al_xGa_1-xAs base layer
7 Emitter electrode
8 Base electrode
9 Collector electrode
10 Semi-insulating GaAs substrate
21 n-type GaAs collector buffer layer
22 GaAs collector layer
23 Internal C-doped p-type GaAs base layer
24 n-type In_0.5Ga_0.5P emitter layer
25 n-type InGaAs emitter cap layer
26 Low resistance external C-doped p-type GaAs base layer
27 Emitter electrode
28 Base electrode
29 Collector electrode
110 Semi-insulating GaAs substrate
101 n-type GaAs collector buffer layer
102 GaAs collector layer
103 C-doped p-type GaAs base layer
104 n-type Al_0.3Ga_0.7As emitter layer
105 n-type InGaAs emitter cap layer
106 Selectively regrown C-doped p-type GaAs base layer
107 Emitter electrode
108 Base electrode
109 Collector electrode

Claims (6)

In a heterojunction bipolar transistor having a base layer including a layer made of C-doped Al _x Ga _1-x As (0 ≦ x ≦ 0.2),
The base layer includes an internal base layer with an emitter layer formed immediately thereon, and an external base layer extending from the internal base layer to the outside of the region where the emitter layer is formed, and the internal base layer The C-H concentration in the external base layer is higher than the C-H concentration in the external base layer, and the current amplification factor β is increased and stabilized by performing initial energization with transistor operation. Heterojunction bipolar transistor. 2. The heterojunction bipolar transistor according to claim 1, wherein an increase rate (β / β ₀ ) of the current amplification factor β after the initial energization is 110% or more with respect to the current amplification factor β ₀ before the initial energization. . The heterojunction bipolar transistor according to claim 1 or 2, wherein an energization current amount at the time of initial energization is 1 kA / cm ² or more. 4. The C—H concentration in the layer made of the C-doped Al _x Ga _1-x As (0 ≦ x ≦ 0.2) is 10% or more of the C concentration. The heterojunction bipolar transistor described in 1. The carrier concentration of the layer made of C-doped Al _x Ga _1-x As (0 ≦ x ≦ 0.2) is 1.4 × 10 ¹⁹ cm ⁻³ to 6.5 × 10 ¹⁹ cm ^−3. The heterojunction bipolar transistor according to any one of claims 1 to 4. In a method for manufacturing a heterojunction bipolar transistor having a base layer including a layer made of C-doped Al _x Ga _1-x As (0 ≦ x ≦ 0.2),
Laminating a C-doped _{Al x Ga 1-x As (} 0 ≦ x ≦ 0.2) as a base layer comprising a layer of a III-V compound semiconductor layer structure on a semiconductor substrate, the III -V Group so as to have a region where the surface of the compound semiconductor layer structure is exposed, the III forming an emitter layer on -V compound semiconductor layer structure, wherein the exposed said surface in III -V compound semiconductor layer structure area and forming a base electrode, after forming the emitter layer, by Nau line heat treatment process prior to forming the base electrode, said surface at said III -V compound semiconductor layer structure the C-H concentration in the external base layer positioned on the exposed area, and lower than C-H concentration in the base layer located immediately below the emitter layer, and, characterized by applying an initial energization with transistor operation Toss Method of manufacturing a heterojunction bipolar transistor.

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