GeSn Light-Emitting Diode with Magnetostrain Source and Preparation Method Thereof

Abstract

The present invention belongs to the technical field of optoelectronic integrated circuits, and particularly relates to a GeSn light-emitting diode with a magnetostrictive strain source and a preparation method thereof. The light-emitting diode includes a substrate layer, a relaxation layer, and an active region arranged in sequence from bottom to top. The active region includes an n+ type layer, an intrinsic layer, and a p+ type layer arranged in sequence from bottom to top; the materials of the relaxation layer and the active region are both GeSn; the active region is a hollow structure, and a strain source is arranged in the active region. The bottom of the strain source extends to the relaxation layer, and the contact between the strain source and the active region and the relaxation layer is isolated by an insulating layer around and at the bottom of the strain source. The strain source can also extend to the bottom of the relaxation layer, and the insulating layer outside the strain source separates it from the active region, the relaxation layer, and the substrate layer. The strain source is composed of a giant magnetostrictive material. A first metal electrode is arranged on the top of the active region. A second metal electrode is arranged on the relaxation layer. The present invention can introduce a large tensile strain into the active region through the strain source, and finally improve the light emission efficiency of the strained GeSn light-emitting diode.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic integrated circuits, and particularly relates to a light-emitting diode with a magnetic strain source based on GeSn material and a preparation method thereof. Background Art

[0002] Under the constraint of Moore's law, the integration degree of integrated circuits has been continuously increasing and the device size has been gradually decreasing. The electrical connection between devices in integrated circuits begins to reach the physical limit. With the rapid development of optoelectronic technology, silicon-based optical interconnection provides a new idea for solving the electrical connection problem in chip integration. In recent years, important breakthroughs have been made in silicon-based optoelectronics in aspects such as photodetectors, modulators, switches, waveguides, etc., but the progress in high-efficiency light-emitting light sources has been very slow. The reason is that common group VI semiconductors such as Si, Ge, and SiGe alloys are indirect bandgap semiconductors. Carriers in the conduction band are almost distributed in the indirect bandgap valleys, and it is very difficult to achieve direct bandgap luminescence recombination. Therefore, the luminescence efficiency of injected carriers is very low.

[0003] The direct bandgap E G,Г of Ge is 0.8 eV, and the indirect bandgap E G,L is 0.664 eV. It has received wide attention because the difference between its direct bandgap and indirect bandgap is only 136 meV. Sn is a negative energy band structure material. The GeSn alloy semiconductor can reduce the direct bandgap by adjusting the composition of Sn, improving the luminescence efficiency of the light-emitting diode. However, due to the very low solid solubility between Ge and Sn and a large lattice mismatch (mismatch ε = 4.2%), the segregation of Sn is caused, making it difficult to obtain GeSn with a high Sn content. Therefore, it is difficult to achieve the change of the GeSn alloy bandgap only by adjusting the composition of Sn. Theoretical research has found that introducing strain can also achieve the adjustment of the GeSn alloy bandgap, and reasonable strain is beneficial to the transformation of the GeSn alloy material to the direct bandgap.

[0004] Theoretical research points out that when the Sn component in the GeSn alloy is 8 at.%, the conduction band energy difference between the direct and indirect bandgaps in the relaxed Ge 0.92 Sn 0.08 alloy is E C,L -E C,Γ = 0.02 eV, the spontaneous emission (the phenomenon that electrons spontaneously transition from a high energy state to a low energy state while emitting light) rate is 0.2×10 26 eV -1 cm -3 s -1 , and the internal quantum efficiency is 0.5%; introducing 0.85% tensile strain Ge 0.92 Sn 0.08 alloy increases the bandgap energy difference to 0.1 eV compared with the relaxed state, and the spontaneous emission rate increases to 2.2×1026 eV -1 cm -3 s -1 , the internal quantum efficiency also increases to 0.9% [Opto - Electronic Advances, 9(1), pp. 180004, 2018]. The introduction of tensile strain promotes the transformation of the GeSn alloy from an indirect bandgap to a direct bandgap material, enhancing the luminescence performance of the alloy material.

[0005] Giant magnetostrictive materials have a large magnetostrictive coefficient, strong magnetostrictive performance, high electro - mechanical conversion rate, and fast response speed. They are an ideal adjustable magnetic strain source. The deformation of giant magnetostrictive materials can be regulated by changing the magnetization state of the materials. For rare - earth giant magnetostrictive materials Tb m Dy 1-m Fe n , with the matching of the contents between Tb and Fe, the orientation of Tb m Dy 1-m Fe n crystal grains can increase from 15.8% to 89.3%, achieving a high orientation of crystal grains, and thus optimizing the magnetostrictive performance of the material. Under a magnetic field strength of 14000 Oe and a pre - pressure of 6 MPa, the magnetostrictive coefficient of Tb 0.3 Dy 0.7 Fe 1.98 reaches 1550 ppm [ELSEVIER, 385(1), pp. 309, 2004]. Summary of the Invention

[0006] In order to improve the luminescence efficiency of silicon - based light sources in optical interconnection integrated circuits, the present invention innovatively proposes a strained GeSn light - emitting diode with an adjustable magnetic strain source. The strain source of the light - emitting diode uses a ternary rare - earth giant magnetostrictive material Tb m Dy 1-m Fe n , where 0.2 ≤ m ≤ 0.3, 1.92 ≤ n ≤ 1.95, the magnetostrictive coefficient is about 2000 ppm, the energy conversion efficiency is about 56%, and the response time is only 10 -6 s. By adjusting the ratio between Tb and Dy and controlling the external magnetic field strength, the present invention introduces adjustable strain in the GeSn alloy, thereby changing the energy band structure of GeSn and achieving the purpose of improving the luminescence performance of the GeSn light - emitting diode.

[0007] The technical solution adopted by the present invention to achieve the above - mentioned purpose is as follows:

[0008] A GeSn light - emitting diode with a magnetic strain source, the structure of which includes a substrate layer, a relaxation layer, and an active region arranged in sequence from bottom to top. The active region includes an n - type layer arranged in sequence from bottom to top+ type layer, intrinsic layer, and p + type layer;

[0009] The materials of the relaxation layer and the active region are both GeSn;

[0010] The active region is a hollow structure, and a strain source is arranged in the active region. Further, the active region can be set as a hollow cylinder, and the strain source is also cylindrical. The bottom of the strain source extends to the relaxation layer, and the contact between the strain source and the active region and the relaxation layer is isolated by an insulating layer around and at the bottom of the strain source. The strain source can also extend to the bottom of the relaxation layer, and the insulating layer outside the strain source separates it from the active region, the relaxation layer, and the substrate layer. The strain source is composed of a giant magnetostrictive material.

[0011] The p + type layer is provided with a first metal electrode on the top, that is, on the top of the active region. A second metal electrode is provided on the relaxation layer.

[0012] Furthermore, the first metal electrode on the top of the active region is annular; the second metal electrode is in contact with the relaxation layer, and the height of the second metal electrode does not exceed the n + type layer and is not in contact with the first metal electrode.

[0013] The substrate layer is a GeOI substrate layer, the relaxation layer is a phosphorus heavily doped n + type GeSn relaxation layer, and the insulating layer is a SiO2 insulating film.

[0014] The general formula of the GeSn material in the active region is Ge 1-x Sn x , n + type layer uses phosphorus heavily doped Ge 1-x Sn x material, the intrinsic layer uses Ge 1-x Sn x material, p + type layer uses boron heavily doped Ge 1-x Sn x material, the relaxation layer is phosphorus heavily doped Ge 1-y Sn y material, where 0.8 ≤ x ≤ 1.5 and y > x.

[0015] The strain source uses the giant magnetostrictive material Tb m Dy 1-m Fe n , where 0.2 ≤ m ≤ 0.3 and 1.92 ≤ n ≤ 1.95.

[0016] The preparation method of the above GeSn light-emitting diode with a magnetic strain source includes the following steps:

[0017] Step 1: Grow a GeSn relaxed layer on a substrate layer by using molecular beam epitaxy growth technology;

[0018] Step 2: Sequentially grow an n + -type layer, an intrinsic layer, and a p + -type layer on the relaxed layer; where the p + -type layer is formed by implanting boron ions into GeSn material; the n + -type layer is formed by implanting phosphorus ions into GeSn material;

[0019] Step 3: Use dry etching to etch all material layers except the substrate layer into a hollow structure, and then etch the outer periphery of the active region so that its outer diameter is smaller than that of the relaxed layer.

[0020] Specifically, use dry etching to etch all material layers except the substrate into a hollow circular cylinder with an outer diameter of 8 μm and an inner diameter of 3 μm, and then etch the active region into a circular cylinder with an outer diameter of 5 μm;

[0021] Step 4: Deposit an insulating layer on the inner side of the hollow structure by using chemical vapor deposition;

[0022] Step 5: Fill and grow a giant magnetostrictive material in the hollow structure by using magnetron sputtering technology to form a strain source, and the top of the strain source does not exceed the top of the insulating layer;

[0023] Step 6: Use a lift-off process with glue to form a first metal electrode and a second metal electrode on the top of the active region and above the relaxed layer respectively, where the top of the second metal electrode does not exceed the top of the n + -type layer.

[0024] Compared with existing devices, the beneficial effects of the present invention are as follows:

[0025] The present invention designs a GeSn light-emitting diode with a magnetic strain source, where the active region of the light-emitting diode is a GeSn p-i-n sandwich hollow structure, and the strain source is filled and grown in the hollow structure. A large tensile strain can be introduced into the active region through the strain source. The introduction of the tensile strain can increase the energy difference between the conduction band E C,L -E C,Γ in the GeSn alloy in the active region, thereby changing the carrier distribution in the Γ valley and L valley in the conduction band, enhancing the direct recombination rate of carriers, and improving the light emission efficiency of the strained GeSn light-emitting diode.

[0026] Furthermore, for the strain source of the strained GeSn light-emitting diode structure with adjustable strain in the present invention, a giant magnetostrictive material Tb m Dy 1-m Fe n, Giant magnetostrictive materials have a large magnetostrictive coefficient, strong magnetostrictive performance, high electromechanical conversion rate, and fast response speed. They are an ideal adjustable magnetic strain source. By adjusting the ratio between Tb and Dy and controlling the external magnetic field in the Z-axis direction, the expansion and contraction amount of the strain source is changed, and an adjustable tensile strain in the Z-axis direction is introduced into the GeSn alloy in the diode active region. Description of the Drawings

[0027] Figure 1 It is a three-dimensional schematic diagram of a GeSn light-emitting diode with a magnetic strain source.

[0028] Figure 2 It is a schematic structural diagram of a GeSn light-emitting diode with a magnetic strain source.

[0029] Figure 3 It is an XZ sectional view of a GeSn light-emitting diode with a magnetic strain source.

[0030] Figure 4 It is a processing schematic diagram of step 1 of the preparation method of a GeSn light-emitting diode with a magnetic strain source.

[0031] Figure 5 It is a processing schematic diagram of step 2 of the preparation method of a GeSn light-emitting diode with a magnetic strain source.

[0032] Figure 6 It is a processing schematic diagram of step 3 of the preparation method of a GeSn light-emitting diode with a magnetic strain source.

[0033] Figure 7 It is a processing schematic diagram of step 4 of the preparation method of a GeSn light-emitting diode with a magnetic strain source.

[0034] Figure 8 It is a processing schematic diagram of step 5 of the preparation method of a GeSn light-emitting diode with a magnetic strain source.

[0035] Figure 9 It is a processing schematic diagram of step 6 of the preparation method of a GeSn light-emitting diode with a magnetic strain source.

[0036] Figure 10 It is a magnetostrictive strain diagram of Examples 1 to 3.

[0037] Reference numerals in the drawings: 101 - substrate layer, 102 - relaxation layer, 103 - n + -type layer, 104 - intrinsic layer, 105 - p + -type layer, 106 - insulating layer, 107 - strain source, 108 - first metal electrode, 109 - second metal electrode. Detailed Description of the Invention

[0038] The present invention will be described in more detail below through specific embodiments to facilitate the understanding of the technical solution of the present invention, but it is not used to limit the protection scope of the present invention.

[0039] Embodiment 1: GeSn Light-Emitting Diode with a Magnetostrain Source

[0040] As Figures 1 to 3 shown, the GeSn light-emitting diode with a magnetostrain source has a structure that sequentially includes a substrate layer 101, a relaxation layer 102, and an active region from bottom to top. The active region includes an n + -type layer 103, an intrinsic layer 104, and a p + -type layer 105 arranged in sequence from bottom to top. The active region is cylindrical, and a strain source 107 is arranged therein. The strain source 107 is also cylindrical, and the bottom of the strain source 107 extends to the relaxation layer 102. When the bottom of the strain source 107 extends to the bottom of the relaxation layer 102, strain can be brought to the relaxation layer 102. An insulating layer 106 is arranged on the outer periphery and bottom of the strain source 107 to isolate the relaxation layer 102, the active region, and the substrate layer 101, and the top of the strain source 107 does not exceed the top of the insulating layer 106. A ring-shaped first metal electrode 108 is arranged on the top of the active region, and a second metal electrode 109 is arranged above the relaxation layer 102. The height of the second metal electrode 109 does not exceed the n + -type layer 103 and does not contact the first metal electrode 108.

[0041] The substrate layer 101 is a GeOI substrate layer, the relaxation layer 102 is a relaxed n + -type Ge 1-y Sn y layer, the n + -type layer 103 is an n + -type Ge 1-x Sn x layer, the intrinsic layer 104 is an i Ge 1-x Sn x layer, the p + -type layer 105 is a p + -type Ge 1-x Sn x layer, the insulating layer 106 is a SiO2 insulating film, and the strain source 107 is made of a ternary rare-earth giant magnetostrictive material with a general formula of Tb 0.3 Dy 0.7 Fe 1.95 .

[0042] n + -type Ge 1-x Sn x layer, i Ge 1-x Sn x layer, and p + -type Ge1-x Sn x A p-i-n structure of the active region of a light-emitting diode is composed of layers, and the active region is Ge 1-x Sn x The general formula of the material is Ge 0.92 Sn 0.08 , and the relaxed n+-type Ge 1-y Sn y The general formula of the layer material is Ge 0.915 Sn 0.085 . Under a pre-pressure of 0 MPa, the magnetostrictive strain reaches approximately 1800 ppm under an applied magnetic field of 240 kA / m.

[0043] Preparation of a GeSn light-emitting diode with a magnetic strain source:

[0044] Step 1: As Figure 4 shown, on the GeOI substrate layer 101, grow an n + -type Ge 1-y Sn y relaxed layer 102 by molecular beam epitaxy;

[0045] Step 2: As Figure 5 shown, grow a layer of n + -type Ge 1-x Sn x material, a layer of intrinsic Ge 1- x Sn x material, and a layer of p + -type Ge 1-x Sn x material in sequence on the relaxed layer 102; among them, the p + -type Ge 1-x Sn x material adopts boron ion implantation process to form a p + -type layer 105; the n + -type Ge 1-x Sn x material adopts phosphorus ion implantation process to form an n + -type layer 103; 0.8 ≤ x ≤ 1.5, y > x.

[0046] Step 3: Use dry etching to etch all material layers except the substrate layer 101 into a hollow circular cylinder with an outer diameter of 8 μm and an inner diameter of 3 μm, and then etch the active region into a circular cylinder with an outer diameter of 5 μm. The structure after etching is as Figure 6 shown;

[0047] Step 4: As Figure 7 shown, deposit a SiO2 thin film on the inner side of the hollow columnar structure by chemical vapor deposition to form an insulating layer 106;

[0048] Step 5: As shown in Figure 8 , use the magnetron sputtering process to fill and grow the giant magnetostrictive material Tb m Dy 1-m Fe n in the hollow columnar structure, where 0.2 ≤ m ≤ 0.3 and 1.92 ≤ n ≤ 1.95, to form the strain source 107, and the top of the strain source 107 does not exceed the top of the insulating film 106;

[0049] Step 6: As shown in Figure 9 , use the tape peeling process to form the first metal electrode 108 and the second metal electrode 109 on the top of the annular cylinder and above the relaxation layer respectively, where the top of the second metal electrode does not exceed the top of the n + -type layer 103.

[0050] Example 2

[0051] This example is basically the same as Example 1, except that the strain source is a ternary rare earth giant magnetostrictive material with the general formula Tb 0.27 Dy 0.73 Fe 1.95 . Under a pre-pressure of 0 MPa and an applied magnetic field of 240 kA / m, the magnetostrictive strain can reach approximately 1100 ppm. Compared with Example 1, when the Tb / Dy ratio is changed, the magnetostrictive coefficient changes accordingly.

[0052] Example 3

[0053] This example is basically the same as Example 1, except that the applied magnetic field intensity is changed to 60 kA / m, and at this time the magnetostrictive coefficient reaches 700 ppm. This is because in the free state, the relationship between the magnetostrictive strain and the magnetic induction intensity is S = β (B∥) *B, where β (B∥) = 2CB ∥ is the magnetostrictive strain constant, which is related to the material and is proportional to the constant magnetic induction intensity B ∥ applied to the material, and C is the elastic modulus along the magnetic field direction and the expansion direction. By changing the applied magnetic field, the change of the magnetostrictive strain can be realized, and the purpose of regulating the strain source can also be achieved.

[0054] The above-described examples are only the preferred examples of the present invention and do not limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made according to the structure, features, and principles described in the scope of the present invention patent shall be included in the scope of the present invention's patent application.

Claims

1. A GeSn light-emitting diode with a magnetostrain source, characterized in that, It includes a buffer layer (101), a relaxation layer (102), and an active region which are sequentially arranged from bottom to top, and the active region includes an n ＋ -type layer (103), an intrinsic layer (104), and a p ＋ -type layer (105); The materials of the relaxation layer (102) and the active region are both GeSn; The active region is a hollow structure, and a strain source (107) is arranged in the active region. The bottom of the strain source (107) extends to the relaxation layer (102), and the periphery and bottom surface of the strain source (107) are insulated by an insulating layer (106) to isolate its contact with the active region and the relaxation layer (102); The material of the strain source (107) is a giant magnetostrictive material; A first metal electrode (108) is arranged on the top of the active region, and a second metal electrode (109) is arranged on the relaxation layer (102).

2. The GeSn light-emitting diode with a magnetostrain source according to claim 1, wherein The active region is a hollow cylinder, and the strain source (107) is cylindrical.

3. The GeSn light-emitting diode with a magnetostrain source according to claim 1, characterized in that, The substrate layer (101) is a GeOI substrate layer, and the relaxation layer (102) is a heavily phosphorus-doped n ＋ -type GeSn relaxation layer, and the insulating layer (106) is a SiO2 insulating thin film.

4. The GeSn light-emitting diode with a magnetostrain source according to claim 1, characterized in that, The general formula of the GeSn material used in the active region is Ge 1-x Sn x , n ＋ -type layer (103) is a phosphorus-heavily doped Ge 1-x Sn x material, the intrinsic layer (104) uses Ge 1-x Sn x material, the p ＋ -type layer (105) uses a boron-heavily doped Ge 1-x Sn x material, where 0.8 ≤ x ≤ 1.

5.

5. The GeSn light-emitting diode with a magnetostrain source according to claim 4, characterized in that, The relaxation layer (102) is a phosphorus-heavily doped Ge 1-y Sn y material, wherein, y > x .

6. The GeSn light-emitting diode with a magnetostrain source according to claim 1, wherein The strain source (107) uses a giant magnetostrictive material Tb m Dy 1-m Fe n , where 0.2 ≤ m ≤ 0.3, 1.92 ≤ n ≤ 1.

95.

7. The GeSn light-emitting diode with a magnetostrain source according to claim 1, characterized in that, The first metal electrode (108) on top of the active region is annular; the second metal electrode (109) is in contact with the relaxation layer (102), and the height of the second metal electrode (109) does not exceed the n ＋ -type layer (103).

8. Method for preparing GeSn light-emitting diode with magnetic strain source, characterized in that, It includes the following steps: Step 1: Grow a GeSn relaxation layer (102) on the GeOI substrate layer (101) by molecular beam epitaxy; Step 2: Successively grow an n ＋ -type layer (103), an intrinsic layer (104), and a p ＋ -type layer (105) on the relaxation layer (102); wherein the p ＋ -type layer (105) is formed by using a boron ion implantation process on a GeSn material; the n ＋ -type layer (103) is formed by using a phosphorus ion implantation process on a GeSn material; Step 3: Use dry etching to etch all material layers except the substrate layer (101) into a hollow structure, and then etch the outer periphery of the active region so that its outer diameter is smaller than that of the relaxation layer (102); Step 4: Deposit an insulating layer (106) on the inner side of the hollow structure by chemical vapor deposition; Step 5: Fill and grow a giant magnetostrictive material in the hollow structure by magnetron sputtering to form a strain source (107), and the top of the strain source (107) does not exceed the top of the insulating layer (106); Step 6: Form a first metal electrode (108) and a second metal electrode (109) above the top of the active region and the relaxation layer (102) respectively by using a glue-bonded peeling process, wherein the top of the second metal electrode (109) does not exceed the top of the n ＋ -type layer (103).

9. The method according to claim 8, wherein Step 3 is: Use dry etching to etch all material layers except the substrate layer (101) into a hollow circular cylinder with an outer diameter of 8 μm and an inner diameter of 3 μm, and then etch the active region into a circular cylinder with an outer diameter of 5 μm.

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