A Heterojunction Bipolar Transistor and Its MOCVD Epitaxial Growth Method

Abstract

The present invention belongs to the technical field of heterojunction bipolar transistors, and particularly relates to a heterojunction bipolar transistor and an epitaxial preparation method thereof. In the present invention, a transition layer is provided between the collector region and the base region, and the P-type doped InGaAs transition film layer is grown on the surface of the collector region by pulsed metalorganic chemical vapor deposition. The present invention uses pulsed metalorganic chemical vapor deposition to obtain a P-type doped InGaAs film layer. The pulsed growth method uses an intermittent introduction method of reaction source gases, which can significantly reduce the defect density of the semiconductor epitaxial layer; at the same time, the lattice of the transition layer matches the lattice of the base region, and the quality of the base region material obtained on the transition layer is good and does not change the composition and doping of the base region. Therefore, an HBT epitaxial wafer with low sheet resistance, high gain, and high cut-off frequency can be obtained. Moreover, the present invention does not change the original growth mode of the base region, and the manufacturing cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of heterojunction bipolar transistors, and particularly relates to a heterojunction bipolar transistor and an epitaxial preparation method thereof. Background Art

[0002] A heterojunction bipolar transistor (HBT) is a type of bipolar transistor (BJT) that forms a heterojunction between the emitter and the base using different semiconductor materials. The advantages of HBTs are high current gain and low base resistance. In addition, due to the material properties of the semiconductor layer itself, HBTs prepared by epitaxially growing compound semiconductor layers on GaAs substrates (hereinafter referred to as GaAs HBTs) have a very high electron mobility, which has great advantages in high-frequency applications. For example, GaAs HBTs are commonly used in mobile phones, WiFi terminals and their base stations, such as radio frequency (RF) power amplifiers and other monolithic microwave integrated circuits (MMICs). By using a strained semiconductor layer or a semiconductor layer with a graded composition for bandgap engineering of the base, emitter and / or collector, the performance of GaAs HBTs can be effectively improved. For example, materials such as InGaAs / InGaP, GaAsSb / InGaP and GaAsPBi / InGaP are used for the base region and the emitter region respectively, which can reduce the conduction electron transfer time of the HBT, thereby improving the high-frequency performance of the HBT, such as the high current gain cut-off frequency (ft) and the maximum oscillation frequency (fmax).

[0003] The sheet resistance and carrier concentration of the HBT base layer have a great influence on the gain of the device. Therefore, in the process of epitaxial growth of InGaAs / InGaP HBTs, how to grow InGaAs materials that meet the design requirements in the case of high doping concentration in the base region of GaAs / InGaAs / GaInP HBT transistors and lattice mismatch with the substrate is a difficulty in preparing high-performance HBT epitaxial wafers.

[0004] U.S. Patent US20060081963A1 proposes a bipolar transistor with enhanced base transport. By adjusting the doping profile of the InGaAsN base region, low doping is used in the parts near the emitter region and the collector region, and high doping is used in the middle of the base region to ensure that the total carrier concentration in the base region remains unchanged. This method improves the carrier mobility in the base region by reducing the doping in part of the base region, thereby reducing the sheet resistance of the base region. However, since the InGaAsN base region epitaxial layers with different C dopings have different lattice constants, this growth method poses great difficulties for epitaxial growth and is not suitable for industrial applications. Chinese Patent CN106505100A proposes a heterojunction bipolar transistor. The InGaAs base region is divided into four segments, and the composition of each segment increases from bottom to top, which can reduce the strain of the mismatched InGaAs and avoid the formation of dislocations due to stress relaxation when the growth thickness of InGaAs exceeds the critical thickness, thereby reducing the carrier mobility. This method can obtain a high-quality base region, but it also reduces the In composition in the base region, which to a certain extent reduces the high-frequency characteristics of the HBT device. Summary of the Invention

[0005] The object of the present invention is to provide a heterojunction bipolar transistor and an epitaxial preparation method thereof. The heterojunction bipolar transistor provided by the present invention has the characteristics of low sheet resistance, high gain, and high cut-off frequency. And the epitaxial preparation method provided by the present invention does not change the original growth mode of the base region, has a short growth time, and low manufacturing cost.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides an epitaxial preparation method of a heterojunction bipolar transistor. The heterojunction bipolar transistor includes a substrate 01, a buffer layer 02, a collector ohmic contact layer 03, a collector etch stop layer 04, a collector region 05, a base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter ohmic contact layer 09 sequentially disposed on the surface of the substrate 01;

[0008] The heterojunction bipolar transistor further includes: a transition layer 05-1 disposed between the collector region 05 and the base region 06; the material of the transition layer 05-1 is P-type doped InGaAs;

[0009] The epitaxial preparation method includes the following steps;

[0010] (1) Grow a buffer layer 02, a collector ohmic contact layer 03, a collector etch stop layer 04, and a collector region 05 on the surface of the substrate 01 in sequence;

[0011] (2) A transition layer 05-1 is grown on the surface of the collector region 05, including the following steps: Using AsH3, trimethylindium, and trimethylgallium as reaction source gases, and carbon tetrachloride as a doping source gas, a P-type doped InGaAs is grown on the surface of the collector region 05 by pulsed metalorganic chemical vapor deposition to obtain the transition layer 05-1 on the surface of the collector region 05; The pulsed metalorganic chemical vapor deposition method includes multiple pulse cycles, and the waveform of the pulse cycle is a rectangular wave. During one pulse cycle T1+T2+T3+T4, AsH3 is continuously introduced, trimethylindium, trimethylgallium, and carbon tetrachloride are introduced within the T1 time, and trimethylindium, trimethylgallium, and carbon tetrachloride are not introduced within the T2 time; Trimethylindium, trimethylgallium, and carbon tetrachloride are introduced within the T3 time, and trimethylindium, trimethylgallium, and carbon tetrachloride are not introduced within the T4 time; T1 time < T3 time;

[0012] (3) A base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter region ohmic contact layer 09 are sequentially grown on the surface of the transition layer 05-1 to obtain a heterojunction bipolar transistor.

[0013] Preferably, the thickness of the transition layer 05-1 is 3 to 6 nm.

[0014] Preferably, the doping element of the P-type doped InGaAs is C, and the doping concentration is 1E19 to 5E19 cm -3 .

[0015] Preferably, in step (2), the reaction chamber temperature is set to 500 to 520 °C, the flow rate of AsH3 is 400 sccm, the flow rate of trimethylindium is 30 sccm, the effective flow rate of trimethylgallium is 6 sccm, and the effective flow rate of carbon tetrachloride is 2.8 sccm.

[0016] Preferably, the trimethylgallium is introduced into the reaction chamber through a double dilution pipeline.

[0017] Preferably, the T1 time is set to 3 s, the T2 time is set to 5 s, the T3 time is set to 15 s, and the T4 time is set to 1 s.

[0018] Preferably, the number of repetitions of the pulse cycle is 4 to 8 times.

[0019] Preferably, in steps 1 and 3, the growth methods of the buffer layer 02, the collector ohmic contact layer 03, the collector region corrosion barrier layer 04, the collector region 05, the base region 06, the emitter layer 07, the sub-emitter layer 08, and the emitter region ohmic contact layer 09 are metalorganic chemical vapor deposition methods, and the reaction chamber temperature during growth is independently set to 600 to 650 °C.

[0020] The present invention provides a heterojunction bipolar transistor obtained by the epitaxial preparation method described in the above technical solution. The heterojunction bipolar transistor includes a substrate 01, a buffer layer 02, a collector ohmic contact layer 03, a collector region etch stop layer 04, a collector region 05, a base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter region ohmic contact layer 09, which are sequentially disposed on the surface of the substrate 01;

[0021] The heterojunction bipolar transistor further includes: a transition layer 05-1 disposed between the collector region 05 and the base region 06; the material of the transition layer 05-1 is P-type doped InGaAs.

[0022] The present invention provides an epitaxial preparation method for a heterojunction bipolar transistor. The heterojunction bipolar transistor includes a substrate 01, a buffer layer 02, a collector ohmic contact layer 03, a collector etch stop layer 04, a collector region 05, a base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter region ohmic contact layer 09, which are sequentially arranged on the surface of the substrate 01; the heterojunction bipolar transistor further includes: a transition layer 05-1 disposed between the collector region 05 and the base region 06; the material of the transition layer 05-1 is P-type doped InGaAs; the epitaxial preparation method includes the following steps; (1) grow the buffer layer 02, the collector ohmic contact layer 03, the collector etch stop layer 04, and the collector region 05 on the surface of the substrate 01 in sequence; (2) grow the transition layer 05-1 on the surface of the collector region 05, including the following steps: use AsH3, trimethylindium, trimethylgallium, and carbon tetrachloride as reaction source gases, and adopt pulsed metalorganic chemical vapor deposition method to grow P-type doped InGaAs on the surface of the collector region 05 to obtain the transition layer 05-1 on the surface of the collector region 05; the pulsed metalorganic chemical vapor deposition method includes multiple pulse cycles, and the waveform of the pulse cycle is a rectangular wave. During one pulse cycle T1+T2+T3+T4, AsH3 is continuously introduced, trimethylindium, trimethylgallium, and carbon tetrachloride are introduced during T1 time, and trimethylindium, trimethylgallium, and carbon tetrachloride are not introduced during T2 time; trimethylindium, trimethylgallium, and carbon tetrachloride are introduced during T3 time, and trimethylindium, trimethylgallium, and carbon tetrachloride are not introduced during T4 time; T1 time < T3 time; (3) grow the base region 06, the emitter layer 07, the sub-emitter layer 08, and the emitter region ohmic contact layer 09 on the surface of the transition layer 05-1 in sequence to obtain the heterojunction bipolar transistor. In the present invention, a transition layer 05-1 is disposed between the collector region 05 and the base region 06. The transition layer 05-1 is a P-type doped InGaAs film layer obtained by pulsed metalorganic chemical vapor deposition method. The pulsed growth method adopts the intermittent introduction method of reaction source gases, separates the nucleation process and the growth process of the P-type doped InGaAs film layer, first forms a very thin InGaAs nucleation layer on the surface of the collector region 05 and makes it form a stable state, reduces stacking faults and vacancies, and then grows a P-type doped InGaAs epitaxial layer (transition layer 05-1) with a certain thickness on the basis of the InGaAs nucleation layer, which can significantly reduce the defect density of the semiconductor epitaxial layer; at the same time, the material of the transition layer 05-1 is a P-type doped InGaAs film layer. Therefore, when growing a highly doped InGaAs base region on the transition layer 05-1, the lattice of the transition layer 05-1 can be lattice-matched with the lattice of the base region. The quality of the base region material is good and the In composition and doping of the base region are not changed. Therefore, an HBT epitaxial wafer with low sheet resistance, high gain, and high cut-off frequency can be obtained.

[0023] Moreover, the transition layer 05-1 of the present invention is also prepared by metalorganic chemical vapor deposition (MOCVD), which is the same as the preparation method of other layer structures of the heterojunction bipolar transistor, without changing the original growth mode of the base region, and the manufacturing cost is low.

[0024] Furthermore, in the present invention, the reaction chamber temperature is 500 - 520 °C, the flow rate of AsH3 is 400 sccm, the flow rate of trimethylindium is 30 sccm, the flow rate of trimethylgallium is 6 sccm, and the flow rate of carbon tetrachloride is 2.8 sccm. The present invention controls the reaction chamber temperature to be 500 - 520 °C to achieve low-temperature pulsed deposition; the present invention regulates the high partial pressure ratio of AsH3 (400 sccm), which is beneficial to accelerating the surface atom mobility during growth, enabling atoms to reach the stable state at the lowest energy point faster; at the same time, the flow rates of trimethylindium and trimethylgallium are regulated to control the growth rate of InGaAs to be 0.042 nm / s, which can significantly reduce the defect density of the InGaAs film layer, so that the lattice of the obtained transition layer 05-1 matches the lattice of the base region. At the same time, the flow rate of carbon tetrachloride is regulated, and the obtained highly doped InGaAs base region has good quality and does not change the In component and doping of the base region, and an HBT epitaxial wafer with low sheet resistance, high gain, and high cut-off frequency can be obtained.

[0025] Furthermore, in the present invention, the T1 time is set to 3 s, the T2 time is set to 5 s, the T3 time is set to 15 s, and the T4 time is set to 1 s. The number of repetitions of the pulse period is 4 - 8 times. The present invention controls the pulse switching times of trimethylindium, trimethylgallium, and carbon tetrachloride in the pulse period. Using this pulsed gas flow growth, each cycle takes 24 seconds and the growth thickness is about 0.75 nm. After growing for 5 cycles, that is, after growing for 120 seconds, a transition layer 05-1 with an InGaAs epitaxial layer thickness of 3.75 nm can be obtained. The lattice of the transition layer 05-1 matches the lattice of the base region, and the original growth mode of the base region is not changed. The growth time is short and the manufacturing cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the HBT epitaxial structure provided by the present invention;

[0027] Figure 2 It is a schematic diagram of the low-temperature pulsed growth of the HBT transition layer in the embodiment of the present invention;

[0028] Figure 3 It is the test result of the sheet resistance of the InGaAs base region obtained by the growth in the embodiment of the present invention, std = 0.58%. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention provides an epitaxial preparation method for a heterojunction bipolar transistor, and the heterojunction bipolar transistor includes a substrate 01, a buffer layer 02, a collector ohmic contact layer 03, a collector etch stop layer 04, a collector region 05, a base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter region ohmic contact layer 09, which are sequentially disposed on the surface of the substrate 01;

[0030] The heterojunction bipolar transistor further includes: a transition layer 05-1 disposed between the collector region 05 and the base region 06; the material of the transition layer 05-1 is P-type doped InGaAs;

[0031] The epitaxial preparation method includes the following steps;

[0032] (1) Grow a buffer layer 02, a collector ohmic contact layer 03, a collector etch stop layer 04, and a collector region 05 on the surface of the substrate 01 in sequence;

[0033] (2) Grow a transition layer 05-1 on the surface of the collector region 05, including the following steps: using AsH3, trimethylindium, and trimethylgallium as reaction source gases, using carbon tetrachloride as a doping source gas, and adopting pulsed metal organic chemical vapor deposition to grow P-type doped InGaAs on the surface of the collector region 05 to obtain the transition layer 05-1 on the surface of the collector region 05; the pulsed metal organic chemical vapor deposition includes multiple pulse cycles, the waveform of the pulse cycle is a rectangular wave, within one pulse cycle T1+T2+T3+T4, continuously introduce AsH3, introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T1 time, and do not introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T2 time; introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T3 time, and do not introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T4 time; T1 time < T3 time;

[0034] (3) Grow a base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter region ohmic contact layer 09 on the surface of the transition layer 05-1 in sequence to obtain a heterojunction bipolar transistor.

[0035] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well-known to those skilled in the art.

[0036] The heterojunction bipolar transistor provided by the present invention includes a substrate 01, a buffer layer 02, a collector ohmic contact layer 03, a collector etch stop layer 04, a collector region 05, a base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter region ohmic contact layer 09, which are sequentially disposed on the surface of the substrate 01. In the present invention, the material of the substrate 01 is GaAs. The resistivity of the substrate 01 is 1 to 4×10 8Ω·cm. The thickness of the substrate 01 is 675 μm. The material of the buffer layer 02 is GaAs, the doping element is Si, and the doping concentration is 1E18 cm -3 . The thickness of the buffer layer 02 is 100 nm. The material of the collector ohmic contact layer 03 is GaAs, the doping element is Si, and the doping concentration is 5E18 cm -3 . The thickness of the collector ohmic contact layer 03 is 500 nm. The material of the collector etch stop layer 04 is GaInP, the doping element is Si, and the doping concentration is 5E18 cm -3 . The thickness of the collector etch stop layer 04 is 10 nm. The material of the collector region 05 is GaAs, the doping element is Si, and the doping concentration is 0.5 - 5E17 cm -3 . The thickness of the collector region 05 is 1200 nm. The thickness of the collector etch stop layer 04 is 10 nm. The material of the base region 06 is In 0.06 GaAs, the doping element is C, and the doping concentration is 4E19 m -3 . The thickness of the base region 06 is 50 nm. The material of the emitter layer 07 is GaInP, the doping element is Si, and the doping concentration is 5E17 m -3 . The thickness of the emitter layer 07 is 20 nm. The material of the sub - emitter layer 08 is GaAs, the doping element is Si, and the doping concentration is 5E18 m -3 . The thickness of the sub - emitter layer 08 is 100 nm. The material of the emitter region ohmic contact layer 09 is In 0.5 GaAs, the doping element is Te, and the doping concentration is 2E19 m -3 . The thickness of the emitter region ohmic contact layer 09 is 100 nm.

[0037] The heterojunction bipolar transistor provided by the present invention further includes: a transition layer 05 - 1 disposed between the collector region 05 and the base region 06, and the material of the transition layer 05 - 1 is P - type doped InGaAs. The transition layer 05 - 1 is grown on the surface of the collector region 05 by pulsed metalorganic chemical vapor deposition.

[0038] In the present invention, the thickness of the transition layer 05 - 1 is preferably 3 - 6 nm, specifically preferably 3.75 nm. The doping element of the P - type doped InGaAs is preferably C, and the doping concentration of the P - type doped InGaAs is preferably 1E19 - 5E19 cm -3 .

[0039] The epitaxial preparation method of the heterojunction bipolar transistor according to the above technical solution provided by the present invention further includes growing a buffer layer 02, a collector ohmic contact layer 03, a collector region etch stop layer 04, and a collector region 05 on the surface of the substrate 01 in sequence by metalorganic chemical vapor deposition (MOCVD) before growing the transition layer 05-1. In the present invention, the growth of the buffer layer 02, the collector ohmic contact layer 03, the collector region etch stop layer 04, and the collector region 05 is preferably carried out in an MOCVD system (Aixtron company), the reaction chamber pressure is 100 mbar, the growth temperature is 680 °C, H2 is used as the carrier gas, and one or more of trimethylindium (TMIn), trimethylgallium (TMGa), trimethylaluminum (TMAl), carbon tetrachloride (CCl4), silane (SiH4), trimethylarsine (TMAs), arsine (AsH3), and phosphine (PH3) are used as the reaction source gases to grow a GaAs buffer layer 02, an N-GaAs collector ohmic contact layer 03, a GaInP collector region etch stop layer 04, and a GaAs collector layer 05 in sequence. The present invention has no special requirements for the specific growth methods of the GaAs buffer layer 02, the N-GaAs collector ohmic contact layer 03, the GaInP collector region etch stop layer 04, and the GaAs collector layer 05.

[0040] After obtaining the collector layer 05, the present invention uses AsH3, trimethylindium, and trimethylgallium as the reaction source gases, uses carbon tetrachloride as the doping source gas, and adopts pulsed metalorganic chemical vapor deposition to grow P-type doped InGaAs on the surface of the collector region 05; the pulsed metalorganic chemical vapor deposition includes a plurality of pulse cycles, the waveform of the pulse cycle is a rectangular wave, within one pulse cycle T1+T2+T3+T4, AsH3 is continuously introduced, trimethylindium, trimethylgallium, and carbon tetrachloride are introduced within the T1 time, and trimethylindium, trimethylgallium, and carbon tetrachloride are not introduced within the T2 time; trimethylindium, trimethylgallium, and carbon tetrachloride are introduced within the T3 time, and trimethylindium, trimethylgallium, and carbon tetrachloride are not introduced within the T4 time; the T1 time < the T3 time. Figure 2Schematic diagram of a preferred low-temperature pulsed growth method for growing a transition layer 05-1 on the surface of the collector layer 05 in the present invention. In the present invention, the reaction chamber temperature is preferably 500-520 °C, more preferably 520 °C, the flow rate of AsH3 is preferably 400 sccm, the flow rate of trimethylindium is preferably 30 sccm, the flow rate of trimethylgallium is preferably 6 sccm, and the flow rate of carbon tetrachloride is preferably 2.8 sccm. The trimethylgallium is introduced into the reaction chamber through a double dilution pipeline. In the present invention, the growth of the transition layer 05-1 is preferably carried out in a MOCVD system (Aixtron company), and TMGa is introduced into the reaction chamber through a double dilution pipeline. The Source / Dilute / inject flow rates of its MOCVD system are 30 sccm / 970 sccm / 200 sccm respectively. The gas concentration introduced into the reaction chamber through the double dilution pipeline is calculated by formula 1:

[0041]

[0042] where S is the actual gas flow rate introduced into the reaction chamber, F Source 、F Dilute 、F Inject represent the flow rates of Source, Dilute, and Injetct respectively. Therefore, the flow rate of TMGa introduced into the reaction chamber is 6 sccm. The growth rate of the InGaAs epitaxial layer is linearly related to the flow rates of In and Ga. The growth rate of InGaAs is calculated to be 0.042 nm / s.

[0043] In the present invention, the T1 time is preferably set to 3 s, the T2 time is preferably set to 5 s, the T3 time is preferably set to 15 s, and the T4 time is preferably set to 1 s. The number of repetitions of the pulse period is preferably 4-8 times, more preferably 5 times.

[0044] After obtaining the transition layer 05-1, the epitaxial preparation method of the heterojunction bipolar transistor according to the above technical solution provided by the present invention further includes growing a base region 06, an emitter layer 07, a sub-emitter layer 08, and an emitter region ohmic contact layer 09 on the surface of the transition layer 05-1 to obtain the heterojunction bipolar transistor. The growth of the base region 06, the emitter layer 07, the sub-emitter layer 08, and the emitter region ohmic contact layer 09 is preferably carried out in a MOCVD system (Aixtron), the reaction chamber pressure is 100 mbar, the growth temperature is 680 °C, using H2 as the carrier gas, and one or more of trimethylindium (TMIn), trimethylgallium (TMGa), trimethylaluminum (TMAl), carbon tetrachloride (CCl4), silane (SiH4), trimethylarsine (TMAs), arsine (AsH3), and phosphine (PH3) are used as the reaction source gases to grow the base region 06, the emitter layer 07, the sub-emitter layer 08, and the emitter region ohmic contact layer 09 in sequence. The present invention has no special requirements for the specific growth methods of the base region 06, the emitter layer 07, the sub-emitter layer 08, and the emitter region ohmic contact layer 09.

[0045] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0046] Example 1

[0047] The schematic diagram of the HBT epitaxial structure provided in this example is as Figure 1 shown. Table 1 is an information table of the materials, thicknesses, doping elements, doping concentrations, and corresponding functions of each layer of the HBT epitaxial structure provided in this example. Prepare the junction bipolar transistor according to the Figure 1 shown structure.

[0048] Table 1 Information table of the HBT epitaxial structure provided in Example 1

[0049]

[0050] With a resistivity of 4x10 8GaAs with a resistivity of Ω·cm is used as the growth substrate and placed in an Aixtron MOCVD system for growth. The reaction chamber pressure is 100 mbar, the growth temperature is 680 °C, H2 is used as the carrier gas, and trimethylindium (TMIn), trimethylgallium (TMGa), trimethylaluminum (TMAl), carbon tetrachloride (CCl4), silane (SiH4), trimethylarsine (TMAs), arsine (AsH3), and phosphine (PH3) are used as reaction source gases. TMGa is continuously introduced as the source gas, and SiH4 is used as the doping gas. The source flow rate of TMGa is set to 100 sccm to grow the N-GaAs buffer layer and the N-GaAs collector region ohmic contact layer. Then, AsH3 is switched to PH3, and then TMGa and TMIn are introduced to grow the GaInP etch stop layer. The source flow rate of TMGa used is set to 15 sccm, and the source flow rate of TMIn is 600 sccm. Then, PH3 is switched to AsH3 to grow the GaAs collector region, and the source flow rate of TMGa is set to 100 sccm.

[0051] Then, under the protection of 400 sccm of AsH3 gas, the reaction chamber is slowly cooled to 520 °C, and then TMIn, TMGa, and CCl4 are introduced into the MOCVD reaction chamber in a pulsed manner to slowly grow InGaAs. Among them, the source flow rate of TMIn is set to 30 sccm, the source flow rate of CCl4 is set to 2.8 sccm, and TMGa is introduced into the reaction chamber through a double-dilution pipeline, and its source / dilute / inject flow rates are 30 sccm / 970 sccm / 200 sccm respectively. The gas concentration introduced into the reaction chamber through the double-dilution pipeline can be calculated by the following formula 1:

[0052]

[0053] where S is the actual gas flow rate introduced into the reaction chamber, F Source 、F Dilute 、F Inject represent the flow rates of Source, Dilute, and Inject respectively. Therefore, the flow rate of TMGa introduced into the reaction chamber is 6 sccm, and the growth rate of the InGaAs epitaxial layer is linearly related to the flow rates of In and Ga. The growth rate of InGaAs can be calculated to be 0.042 nm / s.

[0054] Figure 2The relationship between the temperature, the gas pulse injection mode, and the growth time in the MOCVD reaction chamber is given. During the time of T1 = 3 seconds, the pulse is on, and TMGa, TMIn, and CCl4 are injected to grow the InGaAs nucleation layer; during the time of T2 = 5 seconds, the pulse is off, allowing the atoms in the nucleation layer to have enough time to migrate to their lowest energy state; during the time of T3 = 15 seconds, the pulse is on, and TMGa, TMIn, and CCl4 are injected again to grow an epitaxial layer of a certain thickness; during the time of T4 = 1 second, the pulse is off to form a stable epitaxial layer. After the time of T4, it enters the next cycle. In the pulse growth method, a high partial pressure ratio of AsH3 (400 sccm) is always maintained, which is beneficial to accelerating the mobility of surface atoms during growth and enabling the atoms to reach the stable state of the lowest energy more quickly. First, TMGa, TMIn, and CCl4 are injected in short pulses to form a very thin nucleation layer and make it reach a stable state, reducing stacking faults and vacancies. Then, an epitaxial layer of a certain thickness is grown on the basis of the nucleation layer, which can significantly reduce the defect density of the semiconductor epitaxial layer. Using this pulsed gas flow growth, each cycle takes 24 seconds and the growth thickness is about 0.75 nm. After growing 5 cycles, that is, after growing for 120 seconds, the thickness of the InGaAs epitaxial layer is 3.75 nm. Then, the temperature of the reaction chamber is raised to 650 °C to grow an InGaAs base region with a doping concentration of 5E19 cm -3 Then, an InGaP emitter region, a GaAs sub-emitter region, and an InGaAs ohmic contact layer are grown to form a complete HBT epitaxial structure.

[0055] Figure 3 This is the test result of the sheet resistance of the InGaAs base region grown in the embodiment of the present invention, and std = 0.58%.

[0056] It can be seen from Figure 3 that the InGaAs base region obtained in this embodiment has a low sheet resistance and good uniformity.

[0057] It can be seen from the above embodiments that the HBT obtained by the method provided by the present invention has a low sheet resistance, a large gain, and a high cut-off frequency. Reasons: The present invention uses a low-temperature pulsed deposition of an InGaAs lattice transition layer that is lattice-matched to the base region, and then grows a highly doped InGaAs base region. The quality of the base region material is good and the In composition and doping of the base region are not changed. Therefore, an HBT epitaxial wafer with a low sheet resistance, a large gain, and a high cut-off frequency can be obtained. At the same time, the epitaxial cost of the method provided by the present invention is low. Reasons: The low-temperature pulsed deposition of the InGaAs lattice transition layer in the present invention takes only 120 seconds, and the original growth mode of the base region is not changed. The growth time is short and the manufacturing cost is low.

[0058] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can also be obtained based on this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An epitaxial preparation method for a heterojunction bipolar transistor, characterized in that, The heterojunction bipolar transistor includes a substrate (01), a buffer layer (02), a collector ohmic contact layer (03), a collector region etch stop layer (04), a collector region (05), a base region (06), an emitter layer (07), a sub-emitter layer (08), and an emitter region ohmic contact layer (09) that are sequentially disposed on the surface of the substrate (01); The heterojunction bipolar transistor further includes: a transition layer (05-1) disposed between the collector region (05) and the base region (06); the collector region (05) is made of GaAs, the transition layer (05-1) is made of P-type doped InGaAs, and the base region (06) is made of In 0.06 GaAs; The epitaxial preparation method includes the following steps; (1) Grow a buffer layer (02), a collector ohmic contact layer (03), a collector region etch stop layer (04), and a collector region (05) on the surface of the substrate (01) in sequence; (2) Grow a transition layer (05-1) on the surface of the collector region (05), including the following steps: Using AsH3, trimethylindium, and trimethylgallium as reaction source gases, and carbon tetrachloride as a doping source gas, adopt pulsed metalorganic chemical vapor deposition to grow P-type doped InGaAs on the surface of the collector region (05) to obtain a transition layer (05-1) on the surface of the collector region (05); The pulsed metalorganic chemical vapor deposition method includes multiple pulse cycles, and the waveform of the pulse cycle is a rectangular wave. Within one pulse cycle T1+T2+T3+T4, continuously introduce AsH3, introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T1 time, and do not introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T2 time; Introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T3 time, and do not introduce trimethylindium, trimethylgallium, and carbon tetrachloride within T4 time; T1 time < T3 time. First, form a layer of InGaAs nucleation layer on the surface of the collector region (05) to make it in a stable state, reduce stacking faults and vacancies, and then grow a P-type doped InGaAs epitaxial layer on the basis of the InGaAs nucleation layer; (3) Grow a base region (06), an emitter layer (07), a sub-emitter layer (08), and an emitter region ohmic contact layer (09) on the surface of the transition layer (05-1) in sequence to obtain a heterojunction bipolar transistor.

2. The epitaxial preparation method according to claim 1, characterized in that, The thickness of the transition layer (05-1) is 3 to 6 nm.

3. The epitaxial preparation method according to claim 1, characterized in that The doping element of the P-type doped InGaAs is C, and the doping concentration is 1E19 to 5E19 cm -3 .

4. The epitaxial preparation method according to claim 1, wherein In step (2), the reaction chamber temperature is set to 500 to 520 °C, the flow rate of AsH3 is 400 sccm, the flow rate of trimethylindium is 30 sccm, the effective flow rate of trimethylgallium is 6 sccm, and the effective flow rate of carbon tetrachloride is 2.8 sccm.

5. The epitaxial preparation method according to claim 1, wherein The trimethylgallium is introduced into the reaction chamber through a double dilution pipeline.

6. The epitaxial preparation method according to claim 1 or 4, characterized in that, The T1 time is set to 3 s, the T2 time is set to 5 s, the T3 time is set to 15 s, and the T4 time is set to 1 s.

7. The preparation method according to claim 1 or 4, characterized in that The number of repetitions of the pulse cycle is 4 to 8 times.

8. The epitaxial preparation method according to claim 1, wherein In steps (1) and (3), the growth methods of the buffer layer (02), the collector ohmic contact layer (03), the collector region etch stop layer (04), the collector region (05), the base region (06), the emitter layer (07), the sub-emitter layer (08), and the emitter region ohmic contact layer (09) are metalorganic chemical vapor deposition, and the reaction chamber temperature during growth is independently set to 600 to 650 °C.

9. The heterojunction bipolar transistor obtained by the epitaxial preparation method according to any one of claims 1 to 8, characterized in that, The heterojunction bipolar transistor includes a substrate (01), a buffer layer (02), a collector ohmic contact layer (03), a collector region etch stop layer (04), a collector region (05), a base region (06), an emitter layer (07), a sub-emitter layer (08), and an emitter region ohmic contact layer (09) that are sequentially disposed on the surface of the substrate (01); The heterojunction bipolar transistor further includes: a transition layer (05-1) disposed between the collector region (05) and the base region (06); the material of the transition layer (05-1) is P-type doped InGaAs.

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