Epitaxial layer structure of a doped InSb thin film and its preparation process

Abstract

The present invention provides an epitaxial layer structure of a doped InSb film and a preparation process thereof. Based on the MOCVD process, the InSb:Te layer and the InSb layer are periodically and alternately grown to form a doped InSb functional layer of a Hall element, which can increase the band gap of the InSb material and reduce the temperature coefficient of the InSb thin film Hall element; further, the epitaxial layer structure and preparation process provided by the present invention can achieve uniform doping and avoid excessive Te doping, and can reduce the defect density and surface state density of the doped InSb functional layer, thereby improving the sensitivity of the InSb Hall element and reducing the background noise of the Hall element. In addition, the epitaxial layer structure and preparation process of the doped InSb film provided by the present invention further improve the growth process, material and thickness of the buffer layer and the gradient layer, reduce the lattice mismatch between the substrate and the InSb film, reduce the dislocation density of the InSb film caused by the mismatch, and grow an InSb film with a higher mobility, thereby obtaining a higher sensitivity on the Hall element.

Description

Technical Field

[0001] The present invention relates to the field of Hall sensors, and in particular to an epitaxial layer structure of a doped InSb film used on a Hall element and a preparation process thereof. Background Art

[0002] The Hall element is a magnetic sensor component that uses the Hall effect. It is generally used to detect magnetic fields and their changes. It is widely used in automotive, industrial and consumer electronic products. The important parameter of the Hall element is sensitivity. The sensitivity of the Hall element is positively correlated with the carrier mobility of its bulk material. Highly sensitive Hall elements are more likely to accurately detect extremely small magnetic fields and their changes.

[0003] Existing high-sensitivity Hall elements generally use compound semiconductors as the bulk material. Compared with traditional Si material Hall elements, compound semiconductor Hall elements have more advantages in sensitivity. Among them, InSb Hall elements have the highest sensitivity, and their electron mobility can reach up to 78000cm2 / Vs, which is much higher than Si materials and other compound semiconductors. Although InSb Hall elements have excellent sensitivity and signal-to-noise ratio, there are still many problems in their current use:

[0004] (1) Since the band gap of InSb is narrow, only 0.17 eV at room temperature, it has weak binding ability for valence electrons and is easily excited by heat to jump to the conduction band. Therefore, the sensitivity temperature coefficient of InSb Hall element is large and unstable. It has poor working stability in low and high temperature environments, and its sensitivity is significantly reduced, which limits its wider application scenarios.

[0005] (2) The background noise of InSb Hall elements includes thermal noise, shot noise, 1 / f noise, and GR noise. The above noise is related to carrier motion, film material defects, and film material inhomogeneity. Conventional InSb Hall elements use non-doped InSb thin film materials as functional layers, and the background noise generally exceeds 6μV / √Hz (0~1KHz voltage noise spectral density integral value), which is not suitable for application scenarios with ultra-high signal-to-noise ratio requirements. For example, conventional InSb Hall elements use a vacuum evaporation process to prepare undoped InSb thin films (i.e., the Hall element sensing functional layer). The film layer has obvious defect density and surface states, and the background noise is relatively large.

[0006] At present, Te-doped InSb thin films are used to replace undoped InSb thin films in order to solve the above two problems. However, the vacuum evaporation method or MOCVD process used to prepare Te-doped InSb thin films is generally doped. The biggest problem is that the control of InSb components and Te doping amount is low in precision, and the uniformity of Te doping is average, which affects the numerical level of electron mobility. The noise value of the Hall element prepared in this way is high, which in turn affects the sensitivity and signal-to-noise ratio of the Hall element. Summary of the invention

[0007] In view of the above problems, the present invention provides an epitaxial layer structure of a doped InSb thin film, which can realize the angstrom-level precise growth of InSb:Te thin film based on MOCVD epitaxial growth technology, and at the same time, control of Te doping is achieved by controlling the temperature and quantity of precursors (In, Sb, Te). The specific technical solutions include:

[0008] An epitaxial layer structure of a doped InSb thin film, the epitaxial layer structure is grown based on a MOCVD process, comprising:

[0009] substrate;

[0010] A buffer layer covering the upper surface of the substrate;

[0011] a gradient layer covering the upper surface of the buffer layer;

[0012] A doped InSb:Te layer covering the upper surface of the gradient layer;

[0013] An undoped InSb layer covering the upper surface of the doped InSb layer;

[0014] The doped InSb:Te layer and the undoped InSb layer form a single period layer, and a plurality of single period layers are arranged on the gradient layer to form a doped InSb functional layer.

[0015] Preferably, the substrate material is Si, GaAs, GaSb or InAs.

[0016] Preferably, the thickness of the doped InSb:Te layer is a, the thickness of the undoped InSb layer is b, 0.5≤a / b≤5; the number of single-period layers in the doped InSb functional layer is N, 5≤N≤500.

[0017] Preferably, the thickness of the single period layer composed of the doped InSb:Te layer and the undoped InSb layer is c, c=a+b, 2nm≤c≤20nm, and the total thickness of the doped InSb functional layer is 10nm≤N*c≤10000nm.

[0018] Preferably, the thickness of the doped InSb:Te layer is a, and its thickness a / 2 is used as the boundary. In the process of the doped InSb:Te layer growing from the beginning to the thickness of a / 2, the Te doping amount gradually changes from the peak value to the valley value. In the process of the doped InSb:Te layer growing from the thickness of a / 2 to the thickness of a, the Te doping amount gradually changes from the valley value to the peak value.

[0019] Preferably, the peak value of Te doping is 5×10 16 -5×10 17 / cm 3 The valley value of Te doping is 5×10 15 -5×10 16 / cm 3 .

[0020] Preferably, the thickness of the gradient layer is 10 nm-1000 nm; the thickness of the gradient layer film is smaller than the thickness of the buffer layer film.

[0021] A Hall element uses the epitaxial layer structure of the doped InSb film as a magnetic sensing part.

[0022] A method for growing an epitaxial layer structure of a doped InSb thin film based on a MOCVD process, comprising:

[0023] Step 1, growing a buffer layer on a substrate,

[0024] Step 2: growing a gradient layer on the buffer layer.

[0025] Step 3, growing a doped InSb layer on the gradient layer, and growing an undoped InSb layer on the doped InSb layer, the doped InSb:Te layer and the undoped InSb layer form a single period layer, and multiple single period layers are arranged on the gradient layer to form a doped InSb functional layer.

[0026] Preferably, in step 1, the temperature of growing the buffer layer is 500° C.-700° C.;

[0027] In step 2, the growth temperature of the gradient layer is gradually reduced from the growth temperature in step 1 to 500° C.-600° C., and the growth temperature in step 2 is lower than the growth temperature in step 1;

[0028] In step 3, a doped InSb layer and an undoped InSb layer are grown, and the growth temperature is 300° C.-500° C.

[0029] The technical solution of the present invention has the following technical effects:

[0030] (1) InSb:Te thin film is prepared by doping Te element, the band gap of InSb material is increased, and the temperature coefficient of InSb thin film Hall element is reduced. Doping Te is essentially to use In-Te to replace part of In-Sb in the original InSb material. After Te atoms replace Sb atoms, they can also release the same number of electrons, which does not affect the transport properties of semiconductor materials. It can ensure that the electron mobility is at a higher value, and at the same time increase the InSb band gap, so as to prepare InSb thin film Hall element with low temperature drift, high signal-to-noise ratio and high sensitivity.

[0031] (2) The present invention uses the MOCVD process to periodically and alternately grow the InSb:Te layer and the InSb layer. Compared with the prior art of overall doping to form one InSb:Te layer, it has the following advantages:

[0032] A) It can achieve uniform doping, avoiding the problems of reduced carrier mobility, reduced sensitivity of InSb Hall elements, and increased background noise caused by excessive Te doping;

[0033] B) Compared with overall doping, the InSb:Te layer can be cut into many InSb:Te and InSb layers at the nanoscale, that is, many interfaces can be cut out, which can optimize the overall carrier concentration and mobility of the doped InSb thin film functional layer (including the InSb:Te layer and the InSb layer), and optimize the interface state between the InSb:Te layer and the InSb layer, thereby achieving the overall reduction of the defect density, surface state density, and carrier scattering of the doped InSb thin film functional layer, so as to reduce the overall background noise;

[0034] C) By controlling the Te doping content and the thickness of the InSb:Te and InSb layers, the adjustable space of Te doping can be increased at the nanoscale. Te doping can be regulated based on different needs to obtain InSb:Te films with different doping concentrations and different mobilities. The Hall element prepared based on this type of InSb film has a higher signal-to-noise ratio.

[0035] (3) The present invention adopts the MOCVD epitaxial process and further improves the growth process, material and thickness of the buffer layer and the gradient layer, thereby alleviating the lattice mismatch caused by the heteroepitaxial growth between the substrate and the InSb film, reducing the dislocation density of the InSb film caused by the mismatch, and growing an InSb film with higher mobility, thereby obtaining higher sensitivity on the Hall element. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 The present invention provides an epitaxial structure of a doped InSb film grown based on a MOCVD process.

[0038] Figure 2 The structure diagram of the Hall element adopts the epitaxial structure of the doped InSb film grown based on the MOCVD process provided by the present invention as the magnetic sensing sensing part.

[0039] Figure 3 The voltage noise spectral density characteristic curves of samples A, B, and C tested.

[0040] In the figure, 101. substrate, 102. buffer layer, 103. gradient layer, 104. doped InSb:Te layer, 105. undoped InSb layer, 106. doped InSb functional layer, 201. magnetic induction base, 202. adhesion layer, 203. epitaxial layer of doped InSb thin film, 204. electrode functional part, 205. inorganic passivation layer, 206. organic passivation layer, 207. magnetic concentrating component. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0042] The embodiment of the present invention provides an epitaxial layer structure of a doped InSb thin film grown based on a MOCVD process and a growth process thereof, as shown in the attached specification. Figure 1 The epitaxial layer structure growth process includes:

[0043] Step 1, growing a buffer layer 102 on a substrate 101,

[0044] Step 2, growing a gradient layer 103 on the buffer layer 102,

[0045] Step 3, growing a doped InSb:Te layer 104 on the graded layer 103, and growing an undoped InSb layer 105 on the InSb:Te layer 104, the doped InSb:Te layer 104 and the undoped InSb layer 105 form a single period layer, and multiple single period layers are arranged on the graded layer 103 to form a doped InSb functional layer 106.

[0046] In this embodiment, a process of alternately growing the doped InSb:Te layer 104 and the undoped InSb layer 105 is adopted. Compared with the prior art of forming the InSb:Te layer by overall doping, that is, only one InSb:Te layer, this has the following advantages:

[0047] (1) Uniform doping of Te atoms can be achieved to avoid excessive Te doping;

[0048] Te atoms have a strong diffusion effect in InSb. When using MOCVD epitaxial growth of InSb:Te thin film, a trace amount of Te can achieve a large doping effect. The doped InSb layer 104 and the undoped InSb layer 105 are grown alternately, that is, the diffusion effect of Te atoms is utilized so that the Te atoms in the doped InSb layer 104 can diffuse into the undoped InSb layer 105. Since the thickness of the doped InSb layer 104 and the undoped InSb layer 105 are both in the nanometer range, the diffusion of Te can achieve a basically uniform effect in the two layers, that is, the final doped InSb layer 104 and the undoped InSb layer 105 both have the function of InSb:Te. The convenience of this structure is that it can achieve more precise control of the Te doping amount, avoiding the problem that when the overall doping forms the InSb:Te layer, the Te doping amount is too high, resulting in a decrease in mobility, and then resulting in a decrease in the sensitivity of the InSb Hall element and an increase in the background noise.

[0049] (2) It can alleviate lattice mismatch and thus reduce background noise;

[0050] Growing InSb thin film on a heterogeneous substrate (Si, GaAs, InAs, GaSb, etc.) is heteroepitaxial growth. There is an obvious lattice mismatch between InSb and the substrate, resulting in a large defect density and surface state density of the InSb thin film, resulting in a large background noise of the InSb thin film Hall chip. The present invention uses Te doping, which can be used to adjust the electrical properties of the InSb thin film, adjust the carrier concentration, reduce the defect density and surface state density, and thus reduce the background noise.

[0051] On this basis, the existing InSb:Te layer adopts overall doping, and there is surface state density at the upper and lower interfaces, and there is a certain defect density inside. In this embodiment, the periodic alternating growth process of InSb:Te and InSb layers is adopted, and the InSb:Te as a whole can be cut into many InSb:Te and InSb layers at the nanoscale, that is, many interfaces are cut out, and the surface state can be fully recombinated, thereby realizing the overall reduction of defect density and surface state density, so that the background noise of the InSb thin film Hall chip is further reduced.

[0052] Furthermore, in order to achieve a more uniform overall doping effect of the doped InSb functional layer 106, the present embodiment adopts a gradual doping method for the doped InSb:Te layer 104. Specifically, the thickness of the doped InSb:Te layer 104 is a, and its a / 2 thickness is used as a boundary. In the process of the doped InSb:Te layer growing from the beginning to the thickness of a / 2, the Te doping amount gradually changes from the peak value to the valley value. In the process of the doped InSb:Te layer growing from the thickness of a / 2 to the thickness of a, the Te doping amount gradually changes from the valley value to the peak value. Preferably, the peak value of the Te doping amount is 5×10 16 -5×10 17 / cm 3 The valley value of Te doping is 5×10 15 -5×10 16 / cm 3 .

[0053] The above-mentioned gradual doping method for the doped InSb:Te layer 104 has the following advantages:

[0054] (1) Improved electrical properties: The difference in carrier concentration at the interface between the doped layer 104 and the non-doped layer is increased, which can ensure that there are more Te atoms at the interface between the doped layer 104 and the non-doped layer, resulting in a higher carrier concentration and easier diffusion to the non-doped layer, thereby achieving a more uniform doping effect of the InSb functional layer as a whole, i.e., the effect of adjusting the electrical properties of the material by doping as mentioned above is better;

[0055] (2) Reduce thermal stress: Gradient doping can reduce thermal stress, prevent cracks and defects caused by thermal stress, and improve the stability and reliability of the material.

[0056] (3) Improving carrier mobility: Gradient doping can reduce the scattering of ionized impurities between the doped layer and the undoped layer, improve the carrier mobility, and improve the sensitivity of the Hall chip.

[0057] Furthermore, the process of periodically alternating the growth of InSb:Te and InSb layers is adopted in this embodiment, and the adjustable space of Te doping can be increased at the nanoscale by controlling the Te doping content and the thickness of the InSb:Te layer and the InSb layer. Te doping can be regulated based on different needs to obtain InSb:Te films with different doping concentrations. The Hall element prepared based on this type of InSb film has a higher signal-to-noise ratio.

[0058] Preferably, the thickness a of the doped InSb layer 104 and the thickness b of the undoped InSb layer 105 satisfy 0.5≤ a / b ≤5. It has been found that when a>b, the diffusion effect of Te atoms in the doped InSb:Te layer 104 can be ensured, and the uneven diffusion of Te atoms in the undoped InSb layer 105 can be avoided, which affects the overall electrical performance. More preferably, the thickness a of the doped InSb layer 104 and the thickness b of the undoped InSb layer 105 satisfy 1≤ a / b ≤3.

[0059] Preferably, the thickness of the single period layer composed of the doped InSb:Te layer 104 and the undoped InSb layer 105 is c, c=a+b, 2nm≤c≤20nm, preferably, 5nm≤c≤15nm.

[0060] The number of single-period layers in the doped InSb functional layer is N, 5≤ N ≤500; the thickness of the single-period layer composed of the doped InSb:Te layer and the undoped InSb layer is c, c=a+b, and the total thickness of the doped InSb functional layer is N*c, 10nm≤ N *c≤10000nm. Preferably, 20≤ N ≤400, 5nm≤c ≤15nm, 100nm≤ N *c≤6000nm; more preferably, 20≤ N ≤200, 100nm≤ N *c≤3000nm.

[0061] In this embodiment, the buffer layer 102 and the graded layer 103 are used to optimize the lattice mismatch between the substrate and the InSb film, reduce the dislocation density of the InSb film caused by the mismatch, grow an InSb film with higher mobility, and obtain higher sensitivity on the Hall element.

[0062] Preferably, the buffer layer 102 is a GaAs film with a thickness of 10nm-2000nm. More preferably, the thickness of the buffer layer 102 can be further set to 100nm-1000nm, and its growth temperature is 500°C-700°C. By setting the buffer layer 102, the defects of the substrate can be reduced, providing a better InSb film growth substrate.

[0063] In order to reduce the lattice mismatch problem between the substrate and the InSb functional layer, the graded layer 103 is GaxIn 1-x AsyB 1-yThe film, wherein in the direction from the substrate upward to the InSb layer, x and y are gradually changed from 1 to 0; at the same time, the growth temperature is also gradually changed from the higher temperature of the growth buffer layer GaAs film to the lower temperature, and the optional lower growth temperature range of the gradient layer 103 is 500°C-600°C. For example, the buffer layer 102 is grown at a temperature of 700°C, and during the growth of the gradient layer 103, the temperature is gradually reduced from 700°C to 600°C. Since there is a serious lattice mismatch between InSb and a foreign substrate (Si, GaAs, InAs, GaSb, etc.), the lattice mismatch is as high as 14%. Therefore, a gradient layer 103 is set between the two to achieve lattice gradient, that is, by adding a gradient layer 103 with a lattice constant between the foreign substrate and InSb, a gradient of the lattice constant is achieved, and the GaxIn1-xAsySb1-y film can achieve a lattice constant gradient transition through a continuous transition of components, so as to minimize or even eliminate the lattice mismatch between the foreign substrate and InSb.

[0064] Preferably, the growth temperature of the doped InSb:Te layer 104 and the undoped InSb layer 105 are both 300° C.-500° C.

[0065] Preferably, the thickness of the gradient layer 103 is less than that of the buffer layer 102. The thickness of the gradient layer 103 is 10nm-1000nm.

[0066] In addition, the epitaxial layer structure 203 of the doped InSb thin film grown by MOCVD process in this embodiment is used as the magnetic sensing sensing part, and a magnetic field sensor as shown in the appendix of the specification can be formed. Figure 2 The Hall element shown.

[0067] An undoped InSb thin film prepared by vacuum evaporation, an undoped InSb thin film prepared by MOCVD epitaxial method, and a doped InSb thin film prepared by alternating growth of InSb:Te layer and InSb layer by MOCVD method in this embodiment were used as magnetic sensing sensing parts to form Hall elements as samples A, B, and C. Samples A, B, and C were all driven by a constant voltage of 1V, and the test data of the samples were shown in the following table.

[0068] Table 1 Test data of samples A, B, and C

[0069]

[0070] The noise spectrum density characteristic curves of samples A, B, and C are shown in the attached manual. Figure 3 shown.

[0071] From the above experimental data, it can be seen that sample C uses MOCVD epitaxial growth of Te-doped InSb thin film, which can make its Hall element obtain higher sensitivity, lower noise, higher signal-to-noise ratio, and lower sensitivity temperature coefficient.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An epitaxial layer structure of a doped InSb thin film, the epitaxial layer structure is grown based on a MOCVD process, characterized in that: include: Substrate (101); A buffer layer (102) covering the upper surface of the substrate (101); A gradient layer (103) covering the upper surface of the buffer layer (102); A doped InSb:Te layer (104), covering the upper surface of the gradient layer (103); An undoped InSb layer (105) covering the upper surface of the doped InSb layer (104); The doped InSb:Te layer (104) and the undoped InSb layer (105) form a single period layer, and a plurality of single period layers are arranged on the gradient layer (103) to form a doped InSb functional layer (106); The thickness of the doped InSb:Te layer (104) is a, the thickness of the undoped InSb layer (105) is b, and 0.5≤ a / b ≤5; the number of single-period layers in the doped InSb functional layer (106) is N, and 5≤ N ≤500; The thickness of the single period layer is c, c=a+b, 2nm≤c≤20nm, and the total thickness of the doped InSb functional layer (106) is 10nm≤N*c≤10000nm.

2. The epitaxial layer structure of a doped InSb thin film according to claim 1, characterized in that: The substrate (101) is made of Si, GaAs, GaSb or InAs.

3. The epitaxial layer structure of a doped InSb thin film according to claim 1, characterized in that: The thickness of the doped InSb:Te layer (104) is a, and the thickness a / 2 is used as a boundary. In the process of the doped InSb:Te layer (104) growing from the beginning to the thickness a / 2, the Te doping amount gradually changes from a peak value to a valley value. In the process of the doped InSb:Te layer (104) growing from a / 2 thickness to a thickness a, the Te doping amount gradually changes from a valley value to a peak value.

4. The epitaxial layer structure of a doped InSb thin film according to claim 3, characterized in that: The peak value of Te doping is 5×10 16 -5×10 17 / cm 3 The valley value of Te doping is 5×10 15 -5×10 16 / cm 3 .

5. The epitaxial layer structure of a doped InSb thin film according to claim 1, characterized in that: The gradient layer (103) has a thickness of 10 nm-1000 nm; and the film thickness of the gradient layer (103) is less than the film thickness of the buffer layer (102).

6. A Hall element, using the epitaxial layer structure of the doped InSb thin film as claimed in any one of claims 1 to 5 as a magnetic sensing part.

7. A method for growing an epitaxial layer structure of a doped InSb thin film based on a MOCVD process, characterized in that: include: Step 1, growing a buffer layer (102) on a substrate (101), Step 2, growing a gradient layer (103) on the buffer layer (102), Step 3, growing a doped InSb layer (104) on the graded layer (103), and growing an undoped InSb layer (105) on the doped InSb layer (104), the thickness of the doped InSb:Te layer (104) is a, the thickness of the undoped InSb layer (105) is b, and 0.5≤ a / b ≤5; The doped InSb:Te layer (104) and the undoped InSb layer (105) form a single period layer, the thickness of the single period layer is c, c=a+b, 2nm≤c≤20nm, the number of single period layers in the doped InSb functional layer (106) is N, 5≤N≤500; a plurality of single period layers are arranged on the gradient layer (103) to form the doped InSb functional layer (106); the total thickness of the doped InSb functional layer (106) is 10nm≤N*c≤10000nm.

8. The method for growing an epitaxial layer structure of a doped InSb thin film based on a MOCVD process as claimed in claim 7, wherein in step 1, the temperature for growing the buffer layer (102) is 500° C.-700° C.; In step 2, the growth temperature of the gradient layer (103) is gradually reduced from the growth temperature in step 1 to 500° C.-600° C., and the growth temperature in step 2 is lower than the growth temperature in step 1; In step 3, a doped InSb layer (104) and an undoped InSb layer (105) are grown, both at a growth temperature of 300°C-500°C.

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