Efficient green LED and method for manufacturing

Abstract

The invention concerns a light emitting device comprising a semiconductor layer stack of at least a first layer of a first conductivity type, a second layer of a second conductivity type as well as an active region arranged between the first and the second layer. The semiconductor layer stack is of an InGaAlP material system. The active region comprises a quantum well arranged between a first and a second barrier layer and the active region comprises a central region and an edge region laterally surrounding the central region. Each of the central region and the edge region, and in particular a quantum well portion of the central region and the edge region, comprises a dotation with a first dopant such that the light emitting device is configured to emit light with a wavelength between 540 nm and 560 nm.

Description

[0001] EFFICIENT GREEN LED AND METHOD FOR MANUFACTURING

[0002] The present invention concerns an efficient green LED, in particular pLED, as well as a method for manufacturing the same .

[0003] BACKGROUND pLEDs are optoelectronic devices that comprise a lateral dimension in the range from a few pm to about 40 pm. Such devices provide a variety of different applications , including but not limited to displays .

[0004] For high performance red light emitting devices (LED ) , in particular p-LEDs , an Indium Gallium Aluminium Phosphide ( InGaAlP ) material system is to date the most common used material system. Due to direct-indirect transition occurring at high Aluminium (Al ) contents as well as carrier leakage arising due to reduced band-offset between the quantum well and the barrier material , an efficient green LED, in particular p-LED, using a InGaAlP material system is however challenging and is from an efficiency point of view not in use so far . Therefore , current research focuses on Indium Gallium Nitride ( InGaN ) based green LEDs / pLEDs . However , to achieve green LEDs in Nitride based systems , high Indium ( In ) content is required in the quantum wells region, which again is challenging from epitaxy growth point of view and delivers not the results which are desired .

[0005] There is thus a lack of high-efficacy LEDs in the green-yellow range of the visible spectrum, which in literature is also called the green gap problem .

[0006] It is thus an obj ect of the present application to provide a green LED which overcomes at least some of aforementioned aspects , as well as to provide a method for manufacturing such an LED .

[0007] SUMMARY OF THE INVENTION This and other obj ects are addressed by the subj ect matter of the independent claims . Features and further aspects of the proposed principles are outlined in the dependent claims .

[0008] Local quantum well intermixing induced by controllable diffusion of a dopant into the active region of a semiconductor material creates a higher bandgap material at the sidewalls which minimizes carrier leakage and is a way to fabricate efficient LEDs emitting light with a wavelength higher than 600 nm. The inventors now propose to use a similar technique to fabricate highly efficient green LEDs of an InGaAlP system however not using local quantum well intermixing but intermixing the quantum well of an LED in a larger scale . By means of this , a higher band gap material can be created throughout the whole lateral extensions of the active region of the LED, wherein the material properties of the active region as well as the parameters of the quantum well intermixing can be tuned such that an emission of higher energy green light can be achieved . Hence , the idea of the invention is to address the "Green-Gap" problem via quantum well intermixing in an InGaAlP system. By means of the quantum well intermixing a graded active region can also be realized that would be difficult to be created directly by only growing appropriate layers on top of each other .

[0009] The quantum well intermixing thereby relies on the effect that doping an appropriate dopant into the active region of a semiconductor layer stack causes a diffusion process of atoms in the active region . In particular, the doping causes a diffusion between a barrier layer and a quantum well of the active region, whereby the barrier layer and the quantum well have a different concentration with regard to one or more compounds . The doping in particular causes an intermixing of the compound concentrations within the two layers . This intermixing of the compound concentrations within the two layers in turn enlarges the bandgap within the quantum well and allows an emission of light with a higher energy, in particular green light . By means of the quantum well intermixing for example the Al content in the quantum well can be increased ( decreased in the barrier layer ) due to Al atoms of the barrier layer (with a higher Al concentration and thus a lower Ga concentration ) intermix with Ga atoms of the quantum well (with a higher Ga concentration and thus a lower Al concentration ) . In addition, or as an alternative , by means of the quantum well intermixing for example the In content in the quantum well can be decreased ( increased in the barrier layer ) due to Ga atoms of the barrier layer (with a lower In concentration and thus a higher Ga concentration ) intermix with In atoms of the quantum well (with a higher In concentration and thus a lower Ga concentration ) . Increasing the Al content in the quantum well and / or decreasing the In content in the quantum well thereby has the effect of enlarging the bandgap within the quantum well to allow an emission of light with a higher energy, in particular green light . Combining both effects allows to enlarge the bandgap within the quantum well with less intermixing . Hence combining both effects allows to enlarge the bandgap within the quantum well with doping less dopant into the active region .

[0010] According to a first aspect , a light emitting device comprising a semiconductor layer stack is provided . The semiconductor layer stack comprises at least a first layer of a first conductivity type , a second layer of a second conductivity type as well as an active region arranged between the first and the second layer . The semiconductor layer stack is of an InGaAlP material system but can be also of any other semiconductor material system .

[0011] The active region of the semiconductor layer stack comprises at least one quantum well arranged between a first and a second barrier layer . The active region can however also comprise a multi quantum well structure comprising several quantum wells as well as several barrier layers , wherein each a quantum well is arranged between the two barrier layers .

[0012] In addition, the active region comprises a central region and an edge region laterally surrounding the central region, wherein each the central region and the edge region comprises respective portions of the first and second barrier layer as well as the active region . In other words , the active region can be separated into a central region and an edge region laterally surrounding the central region, with the first and second barrier layer as well as the active region being separated in a respective way . The separation into regions may however not necessarily be understood as a geometrical separation in terms of separate components but may for example be understood as regions of one and the same body . In some embodiments these regions can for example comprise different properties but may also be more or less similar to each other in terms of properties .

[0013] According to the invention each of the central region and the edge region, and in particular a quantum well portion of the central region and the edge region, comprises a dotation with a first dopant . The first dopant can for example be of the first or second conductivity type . By means of the dotation, the light emitting device is configured to emit light with a wavelength between 540 nm and 560 nm, and in particular substantially green light . The dotation with the first dopant can thereby in particular result of a step of quantum well intermixing the central region and the edge region of the active region by diffusing the first dopant into the active region of the semiconductor layer stack .

[0014] According to some aspects , the active region comprises a substantially homogeneous quantum well intermixing across its lateral extension . The central region and the edge region can thus comprise a substantially equal degree of quantum well intermixing . Such a structure can in particular be achieved by conducting a diffusion of the first dopant over a large scale and in particular over the whole area of the light emitting device in particular in terms of lateral extensions .

[0015] According to some aspects , the active region, and in particular the quantum well , comprises a substantially homogeneous dotation with the first dopant across its lateral extension . The central region and the edge region, and in particular a quantum well portion of the central region and the edge region, can thus comprise a substantially equal dotation concentration of the first dopant . Such a structure can in particular be achieved by conducting a diffusion of the first dopant over a large scale and in particular over the whole area of the light emitting device in particular in terms of lateral extensions . According to some aspects , the quantum well comprises at least in its central region a substantially equal bandgap across its lateral extension . In particular the whole quantum well can in theory comprise a substantially equal bandgap across its lateral extension, however due to surface treatment of etched side surfaces of the light emitting device and / or arrangement of further layers on the etched side surfaces of the light emitting device , the bandgap of the quantum well may change in the vicinity of the side surfaces of the light emitting device and thus within the edge region of the active region .

[0016] According to some aspects , the first dopant can be of the first or second conductivity type and can consists of or comprise Silicon ( Si ) , Sulphur ( S ) , Zinc ( Zn ) , Beryllium ( Be ) . Other materials than the materials specified above are however also conceivable as long as they promote a quantum well intermixing of the active region in the desired way .

[0017] According to some aspects , the first barrier layer and / or the second barrier layer are tensile strained layers , with regard to the growth substrate on which the semiconductor layer stack was grown . The first barrier layer and / or the second barrier layer can for example be tensile strained by reducing the In content of the layer ( s ) compared to the In content of the quantum well , or by increasing the In content of the quantum well compared to the In content of the first barrier layer and / or the second barrier layer .

[0018] According to some aspects , the quantum well is -at least at some point of manufacture of the light emitting device and optionally also in the final device- compressively strained, with respect to the growth substrate . The first quantum well can for example be compressively strained by increasing the In content of the quantum well , or by reducing the In content of the first barrier layer and / or the second barrier layer .

[0019] According to some aspects , the first conductivity type is an n-type and the second conductivity type is a p-type The first layer can thus be an n-type semiconductor layer and the second layer can be a p-type semiconductor layer .

[0020] According to some aspects , the light emitting device further comprises a first contact layer arranged on the first layer and / or a second contact layer arranged on the second layer . In particular the first contact layer can be electrically conductive n-type contact layer, whereas the second contact layer can be electrically conductive p-type contact layer . The first and second contact layer can thereby of the same material system as the semiconductor layer stack but can also be contact layers comprising a metal and / or a transparent conductive oxide (TCO ) such as for example indium tin oxide ( ITO ) . By means of the first and second contact layer a first and a second potential can be applied to the light emitting device to operate the light emitting device in a desired manner .

[0021] According to some aspects , the semiconductor layer stack further comprises a first cladding layer arranged between the first contact layer and the first barrier layer and / or a second cladding layer arranged between the second contact layer and the second barrier layer .

[0022] According to some aspects , the first and / or second barrier layer comprise an Al content at least 2 times larger than the Al content of the quantum well . In addition, or as an alternative , the first and / or second barrier layer comprise an In content maximum 1 . 3 times lower than the In content of the quantum well . In other words , the quantum well can comprise an Al content maximum 2 times lower than the Al content of the first and / or second barrier layer , and / or the quantum well can comprise an In content at least 1 . 3 times larger than the In content of the first and / or second barrier layer .

[0023] According to some aspects , the In content can be mostly the same in the quantum well and the barrier layers of the active region of the LED and a quantum well intermixing using the first dopant thus mainly happens due to interdiffusion of Gallium (Ga ) and Al atoms . By only this , it can be already achieved a light emitting device being configured to emit green light with a wavelength around 540 nm to 560 nm.

[0024] A quantum well intermixing with the In content being mostly the same in the quantum well and the barrier layer ( s ) of the active region can however cause a high amount of the first dopant in the active region, which is in some cases not desirable for reliability issues . According to some aspects , it is thus proposed to also force the In atoms in the active region to j oin the quantum well intermixing process by deliberately introducing an In concentration difference between the quantum well and the barrier layer ( s ) . For example , in the active region, the barrier layer ( s ) can be tensile strained ( low Indium content ) compared to the quantum well . Upon quantum well intermixing process , a diffusion of the first dopant into the active region will not only cause an Ga-Al intermixing between the quantum well and the barrier layer ( s ) , but also an Ga-In intermixing between the quantum well and the barrier layer ( s ) . In this way, a light emitting device being configured to emit green light with a wavelength around 540 nm to 560 nm can be achieved even at less content of the first dopant .

[0025] Using the steps described, manipulation of the Al and / or In content in the active region can be performed after epi-growth of the semiconductor layer stack to adj ust the band gap of the quantum well in a desired manner . This can be particularly advantageous because growing suitable layers on top of each other to give a comparable active region with a suitable band gap ( as with quantum well mixing according to some of the aspects of the proposed principle ) would be difficult to achieve by using state-of-the-art epitaxial techniques .

[0026] According to some aspects , side surfaces of the semiconductor layer stack are surface treated for example using a chemical surface treatment step such as for example a HF treatment . By means of this a cleaning and / or passivation of the side surfaces can be achieved .

[0027] According to some aspects , the light emitting device further comprises a passivation layer covering side surfaces of the semiconductor layer stack . The passivation layer can in particular be applied to the side surfaces of the semiconductor layer stack after a surface treatment of the side surfaces has been conducted . The passivation layer can for example comprise a material like Aluminium oxide (A1203 ) or Hafnium oxide ( HfOx) .

[0028] According to some aspects , the second layer can comprise a doping with a second dopant , the second dopant being different to the first dopant . The second dopant can in particular result from a second diffusion step diffusing the second dopant into the semiconductor layer stack . The second diffusion is however stopped before the second dopant reaches the active region, thus only or substantially only the second layer comprises the second dopant . The second dopant can in particular be a dopant of the second conductivity type and can enhance the efficiency of the light emitting device by providing for example more electrons or holes in the second layer compared to a second layer without the second dopant .

[0029] The light emitting device can in particular be a small light emitting component / element such as a small LED or p-LED . A p-LED can in particular be a very small LED with edge lengths down to 40 pm, down to 10 pm, down to 5 pm or even less . Such small LEDs can be free of a growth substrate and require a special handling and processing to improve their IQE and light outcoupling efficiency .

[0030] According to a further aspect , a method for manufacturing a light emitting device configured to emit light with a wavelength between 540nm and 560nm is provided . The method can in particular be a method for manufacturing a light emitting device according to at least some of aforementioned aspects . Hence all aspects already described for the light emitting device can in the same way be applied to the method for manufacturing the same .

[0031] The method comprises the following steps :

[0032] Providing a semiconductor layer stack of at least a first layer of a first conductivity type , a second layer of a second conductivity type as well as an active region arranged between the first and the second layer , wherein the active region comprises a quantum well arranged between a first and a second barrier layer, and wherein the active region comprises a central region and an edge region laterally surrounding the central region; and

[0033] Diffusing a first dopant into the semiconductor layer stack such that each of the central region and the edge region, and in particular a quantum well portion of the central region and the edge region, comprises a dotation with the first dopant .

[0034] According to some aspects , the first barrier layer and / or the second barrier layer are tensile strained layers , with regard to a growth substrate on which the semiconductor layer stack is grown . The first barrier layer and / or the second barrier layer can for example be tensile strained by reducing the In content of the layer ( s ) compared to the In content of the quantum well , or by increasing the In content of the quantum well compared to the In content of the first barrier layer and / or the second barrier layer .

[0035] According to some aspects , the step of providing the semiconductor layer stack comprises providing the first and / or second barrier layer with a higher Al content than the quantum well , in particular at least 2 times higher . As a result , the first and / or second barrier layer at the same time comprises a lower Ga content than the quantum well . The step of diffusing the first dopant into the semiconductor layer stack may then cause an intermixing of the Al-Ga concentrations within the barrier layer ( s ) and the quantum well . In particular by means of the quantum well intermixing the Al content in the quantum well is increased ( decreased in the barrier layer ( s ) ) due to Al atoms of the barrier layer ( s ) (with a higher Al concentration and thus a lower Ga concentration ) intermix with Ga atoms of the quantum well (with a higher Ga concentration and thus a lower Al concentration ) . This intermixing of the Al-Ga concentrations within the barrier layer ( s ) and the quantum well in turn enlarges the bandgap within the quantum well and allows an emission of light with a higher energy, in particular green light .

[0036] According to some aspects , the step of providing the semiconductor layer stack comprises providing the first and / or second barrier layer with a lower In content than the quantum well , in particular at least 1 . 3 times lower . As a result , the first and / or second barrier layer at the same time comprises a higher Ga content than the quantum well . The step of diffusing the first dopant into the semiconductor layer stack may then cause an intermixing of the In-Ga concentrations within the barrier layer ( s ) and the quantum well . In particular by means of the quantum well intermixing the In content in the quantum well can be decreased ( increased in the barrier layer ( s ) ) due to Ga atoms of the barrier layer ( s ) (with a lower In concentration and thus a higher Ga concentration ) intermix with In atoms of the quantum well (with a higher In concentration and thus a lower Ga concentration ) . This intermixing of the In-Ga concentrations within the barrier layer ( s ) and the quantum well in turn enlarges the bandgap within the quantum well and allows an emission of light with a higher energy, in particular green light .

[0037] The two aforementioned aspects can either be provided independently of each other, or they can be provided in combination . Increasing the Al content in the quantum well and / or decreasing the In content in the quantum well thereby both has the effect of enlarging the bandgap within the quantum well to allow an emission of light with a higher energy, in particular green light . Combining both effects allows to enlarge the bandgap within the quantum well with less doping of the first dopant and thus less intermixing . Hence combining both effects allows to enlarge the bandgap within the quantum well with doping less dopants into the active region, which can increase the lifetime of the light emitting device .

[0038] According to some aspects , the step of diffusing the first dopant into the semiconductor layer stack is conducted to intermix the Al content of the quantum well and the first and / or second barrier layer , and / or to intermix the In content of the quantum well and the first and / or second barrier layer .

[0039] According to some aspects , the step of diffusing the first dopant into the semiconductor layer stack may be performed from the gas phase . For example , a diffusion of metallic atoms may be performed . An organometallic precursor material may be used in this process . For example , a gaseous precursor material may be provided . According to further embodiments , the diffusion process may be performed from the solid phase . For example , a suitable material may be vapor deposited on the semiconductor layer stack . The dopants are diffused into the material of the semiconductor layer stack by a subsequent temperature treatment step . According to some aspects , the step of diffusing the dopant into the semiconductor layer stack may be performed using ion implantation .

[0040] In particular the step of diffusing the first dopant into the semiconductor layer stack may be performed after the whole semiconductor layer stack has been grown .

[0041] According to some aspects , the step of diffusing the first dopant into the semiconductor layer stack comprises at least a first diffusion step of diffusing the first dopant into the semiconductor layer stack such that the active region, and in particular the quantum well , comprises a substantially homogeneous dotation with the first dopant across its lateral extension .

[0042] According to some aspects , the method comprises a step of surface treating the side surfaces of the semiconductor layer stack by for example using a chemical surface treatment step such as for example a HF treatment . By means of this a cleaning and / or passivation of the side surfaces can be achieved .

[0043] According to some aspects , the method further comprises a step of providing a passivation layer covering side surfaces of the semiconductor layer stack . The passivation layer can in particular be applied to the side surfaces of the semiconductor layer stack after a surface treatment of the side surfaces has been conducted . The passivation layer can for example comprise a material like Aluminium oxide (A12O3) or Hafnium oxide ( HfOx) . The passivation layer can for example be provided along side surfaces of the semiconductor layer stack such that it circumferentially encloses the semiconductor layer stack . In particular the passivation layer is arranged to cover side surfaces at least of the active region . Hence the edge region can be covered with a passivation layer on a side opposite the central region .

[0044] According to some aspects , the method comprises second diffusion step using a second dopant different to the first dopant . By means of the second diffusion step , the second dopant can be diffused into the second layer . The second diffusion can in particular be done on large scale causing a homogeneous dotation in a lateral direction within the second layer . The diffusion is however stopped before the second dopant reaches the active region, thus only or substantially only the second layer comprises the second dopant . The second dopant can in particular be a dopant of the second conductivity type and can enhance the efficiency of the light emitting device by providing for example more electrons or holes in the second layer compared to a second layer without the second dopant .

[0045] SHORT DESCRIPTION OF THE DRAWINGS

[0046] Further aspects and embodiments in accordance with the proposed principle will become apparent in relation to the various embodiments and examples described in detail in connection with the accompanying drawings in which

[0047] Fig . 1 shows a cross section of a light emitting device in accordance with some aspects of the proposed principle ; and

[0048] Fig . 2 shows steps of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle .

[0049] DETAILED DESCRIPTION

[0050] The following embodiments and examples disclose various aspects and their combinations according to the proposed principle . The embodiments and examples are not always to scale . Likewise , different elements can be displayed enlarged or reduced in size to emphasize individual aspects . It goes without saying that the individual aspects of the embodiments and examples shown in the figures can be combined with each other without further ado , without this contradicting the principle according to the invention . Some aspects show a regular structure or form. It should be noted that in practice slight differences and deviations from the ideal form may occur without , however, contradicting the inventive idea .

[0051] In addition, the individual figures and aspects are not necessarily shown in the correct size , nor do the proportions between individual elements have to be essentially correct . Some aspects are highlighted by showing them enlarged . However , terms such as "above" , "over" , "below" , "under" "larger" , "smaller" and the like are correctly represented with regard to the elements in the figures . So it is possible to deduce such relations between the elements based on the figures .

[0052] Figure 1 shows a cross section of a light emitting device 1 in accordance with some aspects of the proposed principle . The light emitting device 1 comprises a semiconductor layer stack 2 of a first layer 3 of a first conductivity type , a second layer 4 of a second conductivity type as well as an active region 5 arranged between the first and the second layer 3 , 4 . The semiconductor layer stack 2 thereby is of an InGaAlP material system.

[0053] In addition, the light emitting device 1 further comprises a first contact layer 9 arranged on the first layer 3 and a second contact layer 10 arranged on the second layer 4 . The first layer 3 is in particular an n-Type layer whereas the second layer 4 is a p-type layer . Hence the first contact layer 9 is an electrically conductive n-type contact layer, whereas the second contact layer 10 is an electrically conductive p-type contact layer . The first and second contact layer can be of the same material system as the semiconductor layer stack 2 but can also be contact layers comprising a metal and / or a transparent conductive oxide (TCO ) such as for example indium tin oxide ( ITO ) . By means of the first and second contact layer 9 , 10 a first and a second potential can be applied to the light emitting device 1 to operate the light emitting device 1 in a desired manner . The active region 5 comprises a quantum well 6 arranged between a first and a second barrier layer 7 , 8 and can be separated into a central region 5a and an edge region 5b laterally surrounding the central region 5a .

[0054] The layers of the semiconductor layer stack 2 are made of the same material system but comprise different compound concentrations . This is the first and a second barrier layer 7 , 8 comprise a higher Al content than the quantum well and the quantum well comprises a higher In content than the first and a second barrier layer 7 , 8 which are therefore highly tensile strained as compared to the quantum well 6 .

[0055] Each of the central region 5a and the edge region 5b, and in particular a quantum well portion of the central region 5a and the edge region 5b, comprises a dotation with a first dopant , for example Si , S , Zn or

[0056] Be . The above mentioned dopants are in particular a catalyst for a quantum well intermixing process within the active region 5 to tune the bandgap of the quantum well 6 such that the light emitting device 1 is configured to emit light with a wavelength between 540 nm and 560 nm.

[0057] In the embodiment shown, the active region 5 comprises a substantially homogeneous quantum well intermixing and thus a substantially homogeneous dotation with the first dopant type across its lateral extension . The central region 5a and the edge region 5b therefore comprise a substantially equal dotation with the first dopant across its lateral extension .

[0058] Figure 2 shows steps of a method for manufacturing a light emitting device 1 in accordance with some aspects of the proposed principle . In a first step SI , a semiconductor layer stack 2 of a first layer 3 of a first conductivity type , a second layer 4 of a second conductivity type as well as an active region 5 arranged between the first and the second layer 3 , 4 is provided . The semiconductor layer stack 2 thereby is of an InGaAlP material system . Further , the active region 5 comprises a quantum well 6 arranged between a first and a second barrier layer 7 , 8 , and the layers of the semiconductor layer stack 2 are made of the same material system but comprise different compound concentrations . This is the first and a second barrier layer 7 , 8 comprise a lower In content than the quantum well which is therefore compressively strained and the quantum well comprises a higher In content than the first and a second barrier layer 7 , 8 which are therefore tensile strained as compared to the quantum well 6 .

[0059] In a second step S2 , a first dopant , for example Si , S , Zn or Be , is diffused into the semiconductor layer stack 2 from the top surface of the second layer 4 such that the quantum well 6 along its whole lateral extension comprises a substantially homogeneous concentration of the first dopant . The diffusion of the first dopant causes a quantum well intermixing in the active region 5 due to which the Al content in the quantum well is increased ( decreased in the second barrier layer 8 ) , as Al atoms of the second barrier layer 8 (with a higher Al concentration and thus a lower Ga concentration ) intermix with Ga atoms of the quantum well 6 (with a higher Ga concentration and thus a lower Al concentration ) , and due to which the In content in the quantum well 6 is decreased ( increased in the second barrier layer 8 ) , as Ga atoms of the second barrier layer 8 (with a lower In concentration and thus a higher Ga concentration) intermix with In atoms of the quantum well 6 (with a higher In concentration and thus a lower Ga concentration ) . This intermixing of the Al-Ga and In-Ga concentrations within the second barrier layer 8 and the quantum well 8 enlarges the bandgap within the quantum well and allows an emission of light with a higher energy, in particular green light .

[0060] In an optional third step S3 , a second diffusion step is conducted, the second diffusion step comprising a diffusion of a second dopant , different to the first dopant diffusing into the second layer 4 . Due to the second diffusion step , the second layer 4 can in addition to the first dopant comprise a substantially homogeneous concentration of the second dopant along its lateral extension . The second dopant can in particular enhance the efficiency of the light emitting device by for example provide more electrons orholes in the second layer than without the second dopant . Therefore , the second dopant can in particular be of the second conductivity type . LIST OF REFERENCES

[0061] 1 light emitting device

[0062] 2 semiconductor layer stack

[0063] 3 first layer

[0064] 4 second layer

[0065] 5 active region

[0066] 5a central region

[0067] 5b edge region

[0068] 6 quantum well

[0069] 7 first barrier layer

[0070] 8 second barrier layer

[0071] 9 first contact layer

[0072] 10 second contact layer

[0073] SI , S2 , S3 steps

Claims

CLAIMS1. Light emitting device (1) comprising a semiconductor layer stack (2) of at least a first layer (3) of a first conductivity type, a second layer (4) of a second conductivity type as well as an active region (5) arranged between the first and the second layer (3, 4) ; wherein the semiconductor layer stack (2) is of an InGaAlP material system; wherein the active region (5) comprises at least one quantum well (6) arranged between a first and a second barrier layer (7, 8) ; wherein the active region (5) comprises a central region (5a) and an edge region (5b) laterally surrounding the central region (5a) ; wherein each of the central region (5a) and the edge region (5b) , and in particular a quantum well portion of the central region (5a) and the edge region (5b) , comprises a dotation with a first dopant; and wherein the light emitting device (1) is configured to emit light with a wavelength between 540nm and 560nm.

2. Light emitting device according to claim 1, wherein the active region (5) comprises a substantially homogeneous quantum well intermixing across its lateral extension.

3. Light emitting device according to claim 1 or 2 , wherein the quantum well (6) comprises at least in its central region (5a) a substantially equal bandgap across its lateral extension .

4. Light emitting device according to any one of the preceding claims, wherein the active region (5) , and in particular the quantum well (6) , comprises a substantially homogeneous dotation with the first dopant across its lateral extension.

5. Light emitting device according to claim 4, wherein the first dopant consists of or comprises Si, S, Zn or Be.

6. Light emitting device according to any one of the preceding claims, wherein the first barrier layer (7) and / or the second barrier layer (8) are tensile strained layers.

7. Light emitting device according to claim 6, wherein the at least one quantum well (6) is a compressively strained layer.

8. Light emitting device according to any one of the preceding claims, wherein the first conductivity type is an n-type and wherein the second conductivity type is a p-type.

9. Light emitting device according to any one of the preceding claims, further comprising a first contact layer (9) arranged on the first layer (3) and / or a second contact layer (10) arranged on the second layer ( 4 ) .

10. Light emitting device according to any one of the preceding claims, wherein the semiconductor layer stack (2) further comprises a first cladding layer arranged between the first layer (3) and the first barrier layer (7) and / or a second cladding layer arranged between the second layer (4) and second barrier layer (8) .

11. Light emitting device according to any one of the preceding claims, wherein the first and / or second barrier layer (7, 8) comprise: an Al content at least 2 times higher than of the quantum well (6) ; and / or an In content maximum 1.3 times lower than of the quantum well (6) .

12. Light emitting device according to any one of the preceding claims, wherein the second layer (4) comprises a dotation with a second dopant different to the first dopant, wherein in particular the second layer (4) comprises a substantially homogeneous dotation with the second dopant across its lateral extension.

13. Method for manufacturing a light emitting device (1) comprising the steps :Providing a semiconductor layer stack (2) of at least a first layer (3) of a first conductivity type, a second layer (4) of a second conductivity type as well as an active region (5) arranged between the first and the second layer (3, 4) , wherein the active region (5) comprises a quantum well (6) arranged between a first and a second barrier layer (7, 8) , and wherein the active region (5) comprises a central region (5a) and an edge region (5b) laterally surrounding the central region (5a) ; andDiffusing a first dopant into the semiconductor layer stack (2) such that each of the central region (5a) and the edge region (5b) , and in particular a quantum well portion of the central region (5a) and the edge region (5b) , comprises a dotation with the first dopant; wherein the light emitting device (1) is configured to emit light with a wavelength between 540 nm and 560 nm.

14. Method according to claim 13, wherein the first barrier layer (7) and / or the second barrier layer (8) are tensile strained layers.

15. Method according to claim 13 or 14, wherein the step of providing the semiconductor layer stack (2) comprises providing the first and / or second barrier layer (7, 8) with a higher Al content than the quantum well (6) , in particular at least 2 times higher.

16. Method according to any one of claims 13 to 15, wherein the step of providing the semiconductor layer stack (2) comprises providing the first and / or second barrier layer (7, 8) with a lower In content than the quantum well (6) , in particular at least 1.3 times lower.

17. Method according to any one of claims 13 to 16,wherein the step of diffusing the first dopant into the semiconductor layer stack (2) is performed from the gas phase and comprises providing a gaseous precursor material.

18. Method according to any one of claims 13 to 17, wherein the step of diffusing the first dopant into the semiconductor layer stack (2) comprises a diffusion step of diffusing the first dopant into the semiconductor layer stack (2) such that the active region (5) , and in particular the quantum well (6) , comprises a substantially homogeneous dotation with the first dopant across its lateral extension.

19. Method according to any one of claim 18, further comprising a step of diffusing a second dopant different to the first dopant into the second layer.

20. Method according to any one of claims 13 to 19, wherein the step of diffusing the first dopant into the semiconductor layer stack (2) is conducted to intermix the Al content of the quantum well (6) and the first and / or second barrier layer (7, 8) ; and / or intermix the In content of the quantum well (6) and the first and / or second barrier layer (7, 8) .

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