Method for manufacturing semiconductor device and optoelectronic device

Abstract

A method for manufacturing a semiconductor device, in particular an optoelectronic device, comprising: providing a growth substrate (10); depositing an n-type doped first layer (20) and depositing an active region (30) on the n-type doped first layer (20); then depositing a second layer (50) on the active region (30); the second layer is doped with Mg in the second layer (50); after depositing Mg, Zn is deposited in the second layer (50) so that the concentration of Zn in the second layer decreases from a first value to a second value in a first region of the second layer adjacent to the active region, the first region being in the range of 5 nm to 200 nm, in particular less than 50 nm.

Description

[0001] Related Applications

[0002] This application claims priority to EP application No. EP 19177113.8 filed on May 28, 2019, the entire contents of which are incorporated herein. Technical Field

[0003] The present invention relates to the production of semiconductor devices, in particular optoelectronic semiconductor devices. The present invention also relates to optoelectronic devices. Background Art

[0004] LED applications - especially for visual devices such as displays - are now facing more and more challenging requirements. On the one hand, the electronic efficiency in optoelectronic devices, i.e. LEDs, etc. - i.e. the fraction of electrons and holes that contribute to the overall generation of emission - should be as high as possible. Such processes that contribute to the electronic efficiency are called radiative recombination processes (RRP) compared to non-radiative recombination processes (NRRP). Both non-radiative recombination processes and radiative recombination processes are generally based on the size of the active area. In particular, the RR process is concentrated in the central area of ​​the active area, while the NRR process mainly occurs at the edge and is caused by disturbances in the semiconductor structure, i.e. caused by the edge, etc.

[0005] In addition, many LEDs need to operate at relatively high current densities. Increasing temperature reduces the efficiency of radiative recombination and increases electron leakage. Therefore, there is a need for methods and devices to improve current efficiency and reduce electron leakage. Summary of the invention

[0006] In one aspect, the present application proposes a method for manufacturing a semiconductor device, particularly an optoelectronic device. The method includes: providing a growth substrate suitable for growing a semiconductor material thereon. To deposit the semiconductor material, several different methods can be used, including but not limited to CVD, MOVD, MEB, etc. The growth substrate may include a lattice structure similar to the material system to be grown. In some cases, the growth substrate is prepared by growing a sacrificial layer or a lattice adjustment layer on top.

[0007] In subsequent steps, one or more semiconductor layers may be deposited onto the growth substrate, including depositing an n-type doped first layer onto the substrate. An active region is deposited onto the n-type doped first layer. The active region is configured to emit electromagnetic radiation when the completed device is operated.

[0008] In some cases, the active region may be intrinsic or it may be doped.

[0009] Then, a second layer is deposited over the active area. The second layer may also be intrinsic, but will be p-type doped at a later stage. In some cases, the second layer is p-type doped when deposited. To this end, Mg is deposited in the second layer. Mg or magnesium acts as an acceptor, thereby forming a p-type dopant. Deposition is performed by diffusion doping. In some cases, diffusion is performed during the deposition of the second layer. In some other cases, the deposition of Mg is performed after the deposition of the second layer.

[0010] There are three main parameters controlling the diffusion process, including dopant concentration, diffusion temperature and diffusion time. These parameters affect the diffusion length of Mg in the second layer. Therefore, by adjusting these parameters, the diffusion length can be controlled, thereby controlling the concentration distribution of the dopant in the second layer. In some cases, these parameters are adjusted so that the concentration of Mg in the second layer is relatively low near or close to the active area. In other words, the diffusion length is set so that Mg is deposited at a certain distance from the active area.

[0011] In a subsequent step of depositing Mg, a second dopant, in particular Zn, is deposited in the second layer. The concentration of Zn in the second layer decreases from a first value to a second value in a first region of the second layer adjacent to the active area, the first region being in the range of 5 nm to 200 nm, in particular less than 50 nm. In some cases, Zn is deposited in the second layer such that the concentration profile has an edge that drops sharply close to the active area.

[0012] It has been found that the Mg dopant in the second layer and the subsequently deposited Zn dopant exchange their positions in the lattice structure, causing a "kick-out" effect of Mg. This effect causes the concentration profile of Zn to drop significantly and have a steep slope in the region between the first dopant in the second layer and the active region.

[0013] Thus, a higher dopant concentration with a steeper slope near the active region will result in improved charge carrier confinement, resulting in higher current density. In addition, in some aspects, using separate masks during deposition of the two dopants, localization of the concentration profile can be achieved using a profile according to the above principles located at a central region of the semiconductor die.

[0014] In some cases, the slope and position of the Zn dopant edge are adjusted by changing the diffusion temperature of Zn during Zn deposition. The steepness of the slope can also be adjusted using the concentration of Zn. In this regard, the diffusion time of Zn, the concentration of Zn, or the diffusion time of Zn can be different compared to the corresponding parameters when depositing Mg. In some aspects, one or more diffusion parameters for Mg deposition can be adjusted so that the diffusion length of Mg is substantially the same as the diffusion length of Zn. Due to the exchange process when depositing Zn, the Mg dopant is replaced by Zn.

[0015] In this regard, the step of depositing Zn may include adjusting a temperature that is different from the temperature during the step of depositing Mg; and / or adjusting a diffusion time that is different from the diffusion time during the step of depositing Mg; and / or adjusting a concentration of Zn that is different than a concentration of Mg. In this regard, adjusting one of these parameters also includes setting and / or adjusting a corresponding profile of such parameters. In some cases, the temperature when depositing Zn is lower than the temperature used for the diffusion process of Mg.

[0016] In some cases, after Zn diffuses through the second layer, the concentration of Zn in the second region adjacent to the first region is greater than the corresponding concentration of Mg in the second region. For example, the concentration of Zn in the second region adjacent to the first region can be 5 to 500 times greater. In some cases, the Zn dopant completely replaces the Mg dopant in the first region and / or the second region. In some other cases, the replacement is almost complete in most of the second layer.

[0017] The decreasing slope of the concentration of Zn in the region closer to the active region may be greater than the slope of the concentration of Mg. In some other aspects, the initial concentrations of Mg and Zn for diffusion may be the same, but due to the substitution process during the deposition of Zn, the Mg dopant is substituted in a large region of the second layer. The Mg concentration may become large on the surface of the second layer. In some portions of the first region, such as in portions close to the second region, Zn may also include a higher concentration than Mg.

[0018] The thickness of the second layer may be 300 nm to 5 μm, in particular greater than 500 nm.

[0019] Some other aspects relate to the generation of the barrier layer. In some aspects, before depositing the second layer, a third semiconductor layer having Al is deposited onto the active area, wherein the concentration of Al increases with increasing distance from the active area. Then, the second semiconductor layer is deposited onto the third semiconductor layer. In some cases, the Al concentration can increase from a first value to a second value, the second value concentration being close to the second layer. Then, the second layer can include an Al concentration that is higher than the second value concentration.

[0020] In some aspects, the step of depositing an active region includes the step of depositing layers having different material compositions to form one or more quantum well structures.

[0021] Some other aspects relate to an optoelectronic device. The optoelectronic device includes an n-doped first layer, a p-doped second layer, and an active region arranged between the n-doped first layer and the p-doped second layer, the active region being configured to emit radiation when the optoelectronic device is in operation. The p-doped second layer includes Mg as a p-type dopant, the Mg as a p-type dopant having a first concentration profile, in which the concentration toward the active region is very low, and the p-doped second layer also includes Zn as a p-type dopant, the Zn as a p-type dopant having a second concentration profile, in which the concentration decreases toward the active region; the second concentration profile includes a larger decreasing slope than the first concentration profile.

[0022] The thickness of the region where the concentration drops from an initial substantially constant value to a lower second value comprises a thickness of 5 nm to 200 nm, particularly a thickness of 5 nm to 25 nm, more particularly a thickness below 10 nm.

[0023] The second layer of the optoelectronic device may include a sublayer adjacent to the active region, the sublayer having a varying Al concentration. In particular, the Al concentration may increase from an initial level directly adjacent to the active region to a second higher level.

[0024] The falling slope of the second concentration profile may be located in the sub-layer, or the falling slope of the second concentration profile may be located at an interface between the sub-layer and the rest of the second layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the following the proposed solution will be explained in more detail using the accompanying drawings, in which:

[0026] Figures 1A to 1G Several processing steps for manufacturing a semiconductor device according to the proposed principles are shown;

[0027] FIG. 2A to FIG. 2C shows the concentration distribution of Mg or Zn according to some aspects of the proposed solution;

[0028] Figure 3 A semiconductor device having a quantum well structure is shown;

[0029] Figure 4 A more detailed view showing the manufacturing steps of a semiconductor device;

[0030] Figure 5 Shows Figure 4 Top view of the structure. DETAILED DESCRIPTION

[0031] Figures 1A to 1G The manufacturing steps of a semiconductor device according to the proposed principle are shown. Figure 1AIn a first step, a growth substrate 10 is provided. The growth substrate may include a suitable material on top of which subsequent semiconductor layers are grown. In some cases, the growth substrate 10 may include a superlattice structure (not shown) deposited on the substrate to serve as a sacrificial layer and / or to align the lattice structure of the semiconductor layer with the underlying substrate.

[0032] Figure 1B The next step is shown in which a first semiconductor layer 20 is deposited on the growth substrate 10. The semiconductor layer is n-type doped. N-type doping can be achieved by diffusion doping or ion doping after growing the layer. Alternatively, an n-type dopant is provided during the growth of the semiconductor layer so that an n-type doped layer is grown. By changing the concentration of the dopant during growth, the concentration profile can be adapted to specific needs and requirements. Various techniques for growing such layers can be used, such as but not limited to MOCVD, CVD, PVD, MBE, etc. One or more of these techniques are also used for subsequent layers. The N-type doped layer can have various current distribution sublayers to reduce local resistance in the semiconductor.

[0033] After deposition of layer 20, set Figure 1C The active region 30 is shown. The active region 30 may be an intrinsic layer as an undoped layer. In this particular example, the active region 30 comprises the same base semiconductor material as the layer 20, such as an InGaAlP-based material, and the thickness of the active region 30 is in the range of about 100 nm to 300 nm.

[0034] Figure 1D The next step after depositing the active area is shown. A barrier layer 40 is deposited on top of the active area 30. The barrier layer 40 has a varying Al concentration, starting from the same value as the Al concentration in the active area 30 to a second higher level. For example, the Al concentration in the barrier layer 40 can be increased from 40% to about 95% or even 100%, resulting in InAlP with no or almost no Ga concentration. The barrier layer 40 reduces the diffusion of p-dopants such as Mg towards the active area.

[0035] Finally, if Figure 1E and Figure 1FAs shown, a second semiconductor layer 50 is deposited onto the barrier layer 40. The second semiconductor layer will be p-type doped with Mg atoms. Similar to the above, p-type doping can be achieved by diffusion doping or ion doping after growing the layer. In the case of a diffusion process. Mg atoms are deposited after growing the second layer. The concentration, diffusion temperature and diffusion time of the Mg atoms can be adjusted so that the Mg concentration has a specific distribution in the layer 50. Due to the barrier layer 40, the Mg atoms stop at this position during the diffusion process. Continuing to diffuse will produce a uniform distribution in the second layer (e.g., a more direct concentration distribution). However, the closer to the barrier layer 40, the concentration of Mg atoms may decrease, but the slope of the decrease is not very large.

[0036] In an alternative solution, Mg atoms can also be added in gaseous form during the deposition process. In such a case, the concentration of Mg can be varied and adjusted to meet the desired requirements. The Mg concentration can be constant during the growth time. Similar to the above, several techniques can be used, including MOCVD, CVD, PVD, MBE, etc. One or more of these techniques are also used for subsequent layers.

[0037] Figure 1G The next processing step is shown. After the second layer 50 is n-doped with Mg atoms to form layer 50', Zn is deposited on the surface of the second layer. By adjusting the temperature of the semiconductor device to an appropriate temperature, a diffusion process of Zn to the second layer occurs. According to the proposed principle, it has been found that Zn replaces Mg atoms within the lattice structure of the second layer. By selecting the corresponding amount of Zn, temperature and diffusion time, Zn will diffuse through the second layer, thereby partially or completely replacing Mg atoms. The maximum depth near Mg, that is, the concentration slope near the barrier layer 40, becomes very steep. During the diffusion process, the Mg concentration in a portion of the second layer decreases due to substitution, while the Zn concentration increases. In some aspects, Zn almost completely replaces Mg. In some other aspects, the concentration of Zn is 5 to 500 times greater than the corresponding concentration of Mg. This process of replacing Mg and diffusion can be controlled so that the slope of the Zn concentration is very steep near the active area. Because Zn is a p-type dopant like Mg, strong carrier confinement can be achieved due to the concentration edge adjacent to the active area. After the diffusion process, the layer 50 ″ comprises a concentration profile of Zn. The semiconductor device may then be further processed (not shown herein), for example by structuring devices and / or forming contact elements.

[0038] FIG. 2A to FIG. 2C An overview of different concentration profiles is shown. Figure 2AIn its left part a semiconductor device similar to the one described with respect to Figure 1 is shown. An active region 30 is formed above the n-doped first layer 20. A barrier layer 40 with a thickness of approximately 200 nm is deposited onto the active region and a second p-doped layer 50' is formed on top of the barrier layer 40.

[0039] exist Figure 2A In the example of , Mg is used as a dopant for the p-type doped layer 50'. After the diffusion process is performed, the concentration of Mg in the layer 50 is substantially constant. In the barrier layer 40, the concentration of the Mg dopant decreases from an initial value of about 5x10^18cm^-3 to 1x10^16cm^-3. Although in this example, a decrease in the concentration profile occurs in the barrier layer 40, the decrease also depends on the initial concentration, the diffusion temperature, and the diffusion time. In some cases, the Mg concentration may have dropped significantly in the layer 50' close to the barrier layer 40, so that the barrier layer 40 effectively prevents Mg from diffusing into the active area.

[0040] Figure 2B A different example is shown, in which after the deposition and diffusion of Mg, Zn has diffused into the layer 50. Zn has replaced Mg in the layer 50 and has fallen in the barrier layer 40 with a strong reduction in its concentration profile. Figure 2A Compared to the Mg concentration in the 20nm, the concentration of Zn drops from about 5x10^18cm^-3 to 1x10^16cm^-3 in only 20nm. This strong drop in concentration brings the edge of the p-type carriers close to the active area, resulting in good carrier confinement. This structure reduces carrier leakage and improves high current efficiency. Similar to the previous, the initial p-type dopant concentration of Zn can be adjusted and set to a high value. Even at such high values ​​that allow high currents, the strong drop in the concentration profile and the steep flanks of the carrier concentration towards the active area provide good carrier confinement.

[0041] During the deposition and diffusion of Zn into the second layer, Zn replaces the previously doped Mg. Thus, the concentration of Zn in the second layer decreases from a first value to a second value in the first region, i.e., in the barrier layer adjacent to the active region, the first region being in the range of 5 nm to 200 nm, in particular less than 50 nm. In some cases, the barrier layer may be part of the second layer. The concentration of Zn in the second layer may be greater than the concentration of Mg in the layer or in a region thereof.

[0042] Figure 2CA similar example with steep sides in the carrier concentration near the active area is shown. However, compared to the previous example, the second p-type doped layer is formed directly onto the active area without any additional barrier layer. As mentioned above, due to the subsequent doping and diffusion steps, the initial Mg as a p-type dopant has been replaced by Zn. In this example, the initial concentration of Zn, the diffusion time and the temperature have been set so that a steep edge of the Zn concentration is formed near a distance of 100nm from the active area. The drop in concentration occurs at a distance of about 10nm, from an initial value of about 10^19cm^-3 to less than 10^17cm^-3.

[0043] Figure 3 An example of a quantum well structure as an active region is shown. Similar structures have the same reference numerals as in the previous examples. The active region 30 having its quantum well structure includes several sub-layers 30A and 30B, and the several sub-layers 30A and 30B include different Al portions. For example, from the InGa in the sub-layer 30A 0,55 Al 0,45 P to InGa in sublayer 30B 0,45 Al 0,55 P changes, the difference in the Al portion of the InGaAlP structure is 10%. Adjacent to the uppermost sublayer 30B, a barrier layer 40 is formed, in which the Al concentration changes from InGa 0,45 Al 0,55 P increases to InAlP.

[0044] Figure 4 A side view of the processing steps for manufacturing a semiconductor device, particularly an optoelectronic device, is shown in more detail. During the manufacturing step, a photomask layer 60 is deposited onto the second layer 50. The mask is then subsequently constructed to form one or more openings 70. Mg is then deposited onto the mask and into the openings 70, and then diffused into the second layer. As shown, the concentration profile is set so that most of the Mg within the second layer 50 forms a p-type doped region 80. In a subsequent step, Zn is deposited onto the mask and into the openings. The Zn then diffuses into the second layer, replacing the Mg atoms in that region. Zn forms a second concentration profile with a higher concentration in a region that is slightly smaller but reaches a depth in the second layer 50 close to the active area 30. Various profiles can be achieved by setting the diffusion temperature and time as well as the Zn concentration. In this regard, Figure 5 Shows Figure 4 An exemplary mask 60 on top of the second layer is used to construct an optoelectronic device.

[0045] The skilled person may combine the above examples in various ways without departing from the spirit and scope of the present invention. The subsequent deposition of Mg and Zn as two different p-type dopants results in steep sides of Zn within the second layer. By adjusting the diffusion parameters, the sides can be positioned close to the barrier or active area. The steep sides make it possible to increase the current through the device, thereby improving its efficiency.

[0046] Reference numerals list

[0047] 10 Growth substrate

[0048] 20 First n-type doped layer

[0049] 30 Active area

[0050] 30A, 30B quantum well sublayer

[0051] 40 Barrier layer

[0052] 50 Second Floor

[0053] 50' Second p-type doping layer (Mg)

[0054] 50” Second p-type doped layer (Zn)

[0055] 60 Mask

[0056] 70 Opening

[0057] 80 Concentration distribution Mg

[0058] 90 Concentration Distribution Zn

Claims

1. A method for manufacturing a semiconductor device, comprising: - providing a growth substrate (10); - depositing a first n-doped layer (20); - depositing an active region (30) on the n-doped first layer (20); - depositing a p-type doped second layer (50) onto the active area (30), wherein the p-type dopant comprises Mg; - Zn is deposited onto the surface of the p-doped second layer (50) so that Zn partially or completely replaces Mg atoms in the p-doped second layer and so that the concentration of Zn in the second layer decreases from a first value to a second value in a first region of the second layer adjacent to the active area, the first region being in the range of 5 nm to 200 nm.

2. The method according to claim 1, wherein: After Zn diffuses through the second layer, a concentration of Zn in a second region adjacent to the first region is greater than a corresponding concentration of Mg in the second region.

3. The method according to claim 1 or 2, wherein: The first value is 5 to 500 times greater than the second value.

4. The method according to claim 1 or 2, wherein: The second value of the Zn concentration is substantially equal to the concentration of Mg in the first region.

5. The method according to claim 1 or 2, wherein: The second layer has a thickness of 300 nm to 5 μm.

6. The method according to claim 1 or 2, wherein: The steps of depositing Mg include: - adjusting the diffusion parameters so that the diffusion length of Mg is significantly shorter than the distance from the surface of the second layer to the first region or the active area.

7. The method according to claim 1 or 2, wherein: The step of depositing Zn comprises at least one of the following steps: - adjusting the temperature, which is different from the temperature during the deposition step of Mg; - Adjusting the diffusion time, which is different from the diffusion time during the deposition step of Mg.

8. The method according to claim 1 or 2, wherein: The step of depositing Mg or the step of depositing Zn comprises: - Arranging a photomask (60) on said second layer (50).

9. The method according to claim 1 or 2, wherein: The steps for depositing the second layer include: - depositing a third semiconductor layer (40) comprising Al, wherein the concentration of Al varies with increasing distance from the active region; - depositing the second layer onto the third semiconductor layer (40).

10. The method according to claim 1 or 2, wherein: The step of depositing the active region (30) comprises the steps of depositing layers having different material compositions to form one or more quantum well structures (30A, 30B).

11. The method according to claim 1 or 2, wherein: The first layer and the second layer include InGaAIP or InAlP.

12. The method according to claim 1 or 2, wherein: The first region is within a range of less than 50 nm.

13. The method according to claim 5, wherein: The thickness of the second layer is greater than 500 nm.

14. The method according to claim 1 or 2, wherein: The semiconductor device is a photovoltaic device.

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