Full-spectrum LED epitaxial growth method capable of reducing wavelength red shift

Abstract

The invention is applicable to the technical field of semiconductors, and provides a full-spectrum LED epitaxial growth method capable of reducing wavelength red shift, a metal organic chemical vapor deposition reaction cavity is adopted for epitaxial material growth, a plurality of V-shaped pits are formed in a light emitting layer, and a Fe-doped GaN layer, a Fe and C co-doped GaN layer and a BGaN layer are introduced into the V-shaped pits, so that the wavelength red shift of the LED is reduced. More holes at room temperature reach the long-wave quantum well on the N side, and the number difference of holes reaching the long-wave quantum well on the N side under the room temperature and thermal state conditions is reduced, so that the dominant wavelength difference value under the room temperature and thermal state conditions is reduced, the wavelength red shift is reduced, the light output power is improved, and the brightness is improved. The technical problems that the dominant wavelength difference value of a full-spectrum LED is large at the room temperature and the thermal working temperature, and the wavelength generates red shift are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a full-spectrum LED epitaxial growth method for reducing wavelength redshift. BACKGROUND

[0002] LEDs have the characteristics of energy saving, long service life, no pollution, rich colors, etc., and are widely used in lighting, mobile phone / computer backlight, automobile, and large screen display, etc. Full-spectrum LED technology uses the unique properties of gallium nitride materials to produce light covering the visible spectrum, so as to achieve a high degree of consistency with the solar spectrum and effectively reduce the damage of light to the eyes. Compared with traditional lighting technology, full-spectrum LEDs can provide more uniform and soft light, reduce the stimulation and burden on the eyes, and help prevent myopia.

[0003] Current full-spectrum LED technology still faces challenges such as thermal stability and reliability. The emission wavelength of full-spectrum LED devices tends to shift towards the long-wave direction as the temperature rises when working at high temperatures (above 80℃). Therefore, in view of the above status, there is an urgent need to provide a full-spectrum LED epitaxial growth method for reducing wavelength redshift to overcome the deficiencies in current practical applications. SUMMARY

[0004] The purpose of the present application is to provide a full-spectrum LED epitaxial growth method for reducing wavelength redshift, which effectively solves the problems in the background art.

[0005] The present application is implemented as follows: a full-spectrum LED epitaxial growth method for reducing wavelength redshift uses a metal organic chemical vapor deposition reaction chamber for epitaxial material growth. The method comprises the following steps: Step one: desorption treatment is performed on the sapphire substrate; Step two: a buffer layer is grown on the sapphire substrate, and the buffer layer is AlN or GaN; Step three: a non-doped GaN layer and a Si-doped N-type GaN layer are grown on the buffer layer; Step four: a reconciliation layer is grown on the Si-doped N-type GaN layer; Step five: a pre-preparation layer is grown on the reconciliation layer; Step six: a light-emitting layer is grown on the pre-preparation layer; Step seven: the temperature, pressure, growth rate, gas, and metal source flow during the growth of the light-emitting layer are controlled to form multiple V-shaped pits in the light-emitting layer using the dislocation extension mechanism; Step eight: a Fe-doped GaN layer, a Fe and C co-doped GaN layer, and a BGaN layer are sequentially grown and filled above the V-shaped pits; Step nine: a Mg-doped P-type GaN layer is grown on the light-emitting layer and the V-shaped pits; Step ten: growing AlGaN electron blocking layer, Al component from high to low along the growth direction; Step eleven: growing Mg-doped GaN layer with light doping; Step twelve: growing Mg-doped GaN layer with heavy doping, completing the fabrication of the epitaxial wafer.

[0006] As a further scheme of the present application: in step four, the adjustment layer is alternately grown low-In-component InGaN well layer and GaN barrier layer, and the number of alternately repeated cycles is 3-6.

[0007] As a further scheme of the present application: in step five, the pre-prepared layer is alternately grown high-In-component InGaN well layer and GaN barrier layer, and the number of alternately repeated cycles is 3-6.

[0008] As a further scheme of the present application: in step six, the light-emitting layer comprises first quantum well layer, second quantum well layer and third quantum well layer grown in sequence, each quantum well layer comprises alternately grown InGaN well layer and barrier layer, and the number of alternately repeated cycles is 2-8.

[0009] As a further scheme of the present application: the first quantum well layer has a light-emitting peak wavelength of 457-470 nm, the second quantum well layer has a light-emitting peak wavelength of 445-457 nm, and the third quantum well layer has a light-emitting peak wavelength of 430-445 nm.

[0010] As a further scheme of the present application: the barrier layer of each quantum well layer is AlGaN / GaN superlattice structure or GaN barrier layer, and the relative spectral intensity of the light-emitting layer under the condition of wavelength 450 nm and color temperature 4000 K is less than 0.6.

[0011] As a further scheme of the present application: in step seven, the V-pit distribution density is 1E8-1E9 cm -2 , and the opening diameter is 220-420 nm.

[0012] As a further scheme of the present application: in step eight, when growing the Fe-doped GaN layer, the Fe source flow is controlled to be 100-150 sccm, and the layer thickness is 100-200 nm; When growing the Fe and C co-doped GaN layer, the Fe source flow is gradually increased from 700 sccm to 900 sccm, the C doping concentration is 3E17-2E18 cm -3 , and the layer thickness is 100-200 nm.

[0013] As a further scheme of the present application: in step eight, the molar content of B atoms in the BGaN layer is 5%-50%, and the BGaN layer fills the entire V-pit.

[0014] As a further aspect of the present application: in step nine, the Mg doping concentration is 8E+19-3E+20 cm -3 ; In step eleven, the Mg doping concentration is 1E+19-3E+20 cm -3 ; In step twelve, the Mg doping concentration is 4E+20-9E+20 cm -3 .

[0015] Compared with the prior art, the beneficial effects of the present application are: By introducing the Fe-doped GaN layer above the V-shaped pit, under the high potential barrier effect of Fe doping, the carrier is forced to distribute laterally, so that a larger area of active region participates in the transport of carriers, thereby introducing more longitudinal current paths, similar to multiple resistors connected in parallel, thus effectively reducing the on-resistance of the device and improving the light output power.

[0016] After introducing the Fe-doped GaN layer to solve the current congestion problem, the Fe and C co-doped GaN layer is introduced again, the height of the electron potential barrier is increased by controlling the Fe source flow to gradually increase from 700sccm to 900sccm, the resistance of the material layer filled in the V-shaped pit is increased, the voltage difference is increased, and the resistance is further increased by C doping, so that the Fe and C co-doped GaN layer becomes a high resistance layer, more holes at room temperature reach the long-wave quantum well on the N side, the difference in the number of holes reaching the long-wave quantum well on the N side under room temperature and thermal conditions is reduced, thereby reducing the WLD (main wavelength) difference under room temperature and thermal conditions, and reducing the wavelength redshift.

[0017] Finally, the BGaN layer is introduced in the V-shaped pit, and the resistivity of the BGaN layer is significantly increased by controlling the molar content of B atoms to be 5%-50%, thereby further promoting more holes at room temperature to migrate to the long-wave quantum well on the N side, so as to reduce the WLD difference under room temperature and thermal conditions, and reduce the wavelength redshift. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0019] Figure 1 Structure diagram of the full-spectrum LED epitaxial wafer prepared by the method of the present application to reduce wavelength redshift.

[0020] In the drawing: 1-sapphire substrate, 2-buffer layer, 3-N-type GaN layer, 4-adjustment layer, 5-preparation layer, 6-light-emitting layer, 7-V-type pit, 8-Fe-doped GaN layer, 9-Fe and C co-doped GaN layer, 10-BGaN layer, 11-Mg-doped P-type GaN layer, 12-AlGaN electron blocking layer, 13-lightly Mg-doped GaN layer, 14-heavily Mg-doped GaN layer. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0022] The present application will be further explained and described below in conjunction with specific embodiments.

[0023] Please refer to Figure 1 The full-spectrum LED epitaxial growth method for reducing wavelength redshift provided by the embodiment of the present application forms multiple V-type pits 7 in the light-emitting layer 6 and introduces Fe-doped GaN layer 8, Fe and C co-doped GaN layer 9, and BGaN layer 10 in the V-type pits 7, so as to promote more holes to reach the long-wave quantum well on the N side at room temperature, reduce the difference in the number of holes reaching the long-wave quantum well on the N side under room temperature and thermal conditions, thereby reducing the difference in the main wavelength under room temperature and thermal conditions, reducing the wavelength redshift, improving the light output power, and enhancing the brightness.

[0024] The method adopts a metal organic chemical vapor deposition reaction chamber to grow epitaxial materials, and specifically includes the following steps: Step one: performing desorption treatment on the sapphire substrate 1; Step two: growing a buffer layer 2 on the sapphire substrate 1, wherein the buffer layer 2 is one of AlN and GaN; Step three: growing an undoped GaN layer and a Si-doped N-type GaN layer 3 on the buffer layer 2; Step four: growing an adjustment layer 4 on the Si-doped N-type GaN layer 3, wherein the adjustment layer 4 is the alternately grown InGaN well layer with low In component and GaN barrier layer, and the alternation cycle number is 3-6 times; Step five: growing a preparation layer 5 on the adjustment layer 4, wherein the preparation layer 5 is the alternately grown InGaN well layer with high In component and GaN barrier layer, and the alternation cycle number is 3-6 times; Step six: growing a light-emitting layer 6 on the pre-prepared layer 5, the light-emitting layer 6 comprising a first quantum well layer, a second quantum well layer and a third quantum well layer grown in sequence, each of the quantum well layers comprising cyclically grown InGaN well layers and barrier layers, the number of cycles being 2-8, wherein the first quantum well layer has a peak wavelength of 457-470 nm, the second quantum well layer has a peak wavelength of 445-457 nm, and the third quantum well layer has a peak wavelength of 430-445 nm, and the barrier layers in the first, second and third quantum well layers are AlGaN / GaN superlattice structures or GaN barrier layers, the light-emitting layer 6 emitting blue light with a relative spectral intensity <0.6 at a wavelength of 450 nm and a color temperature of 4000 K; Step seven: forming a plurality of V-shaped pits 7 in the light-emitting layer 6 by controlling the temperature, pressure, growth rate, gas and metal source flow during the growth of the light-emitting layer 6, and using the dislocation extension mechanism, the V-shaped pits 7 having a distribution density of 1E8-1E9 cm -2 and an opening diameter of 220-420 nm; Step eight: growing and filling a Fe-doped GaN layer 8, a Fe and C co-doped GaN layer 9 and a boron gallium nitride layer 10 in sequence above the V-shaped pits 7, wherein the Fe source flow is controlled to be 100-150 sccm during the growth of the Fe-doped GaN layer 8, the thickness of the Fe-doped GaN layer 8 is 100-200 nm, the Fe source flow is gradually increased from 700 sccm to 900 sccm during the growth of the Fe and C co-doped GaN layer 9, the C doping concentration is 3E17-2E18 cm -3 , the thickness of the Fe and C co-doped GaN layer 9 is 100-200 nm, the molar content of B atoms in the BGaN layer 10 is 5%-50%, and the BGaN layer 10 fills the entire V-shaped pit 7; Step nine: growing a P-type Mg-doped GaN layer 11 on the light-emitting layer 6 and the V-shaped pits 7, the Mg doping concentration being between 8E+19 and 3E+20; Step ten: growing an AlGaN electron blocking layer 12, the Al component decreasing from high to low in the growth direction; Step eleven: growing a lightly Mg-doped GaN layer 13, the Mg doping concentration being between 1E+19 and 3E+20; Step twelve: finally growing a heavily Mg-doped GaN layer 14, the Mg doping concentration being between 4E+20 and 9E+20, and thus the epitaxial wafer is completed.

[0025] The present application solves the technical problems of full-spectrum LED in room temperature (25℃) and thermal state working temperature (higher than 80℃) that the main wavelength difference is large and the wavelength is red-shifted. The beneficial effects are as follows: By introducing Fe-doped GaN layer 8 above V-pit 7, under the high potential barrier effect of Fe-doping, the carrier is forced to distribute laterally, so that a larger area of active region is involved in the transport of carriers, thereby introducing more longitudinal current paths, similar to multiple resistors connected in parallel, thus effectively reducing the on-resistance of the device and improving the optical output power.

[0026] When the problem of current congestion is solved by introducing Fe-doped GaN layer 8, Fe and C co-doped GaN layer 9 is introduced at this time, by gradually increasing the Fe source flow from 700 sccm to 900 sccm to increase the electron barrier height, the resistance of the material layer filled in V-pit 7 is increased, the voltage difference is increased, and at the same time, the resistance is further increased by C doping, so that the Fe and C co-doped GaN layer 9 becomes a high resistance layer, which promotes more holes to reach the long-wave quantum well on the N side at room temperature, reduces the difference in the number of holes reaching the long-wave quantum well on the N side at room temperature and hot state, thereby reducing the difference in WLD (main wavelength) at room temperature and hot state, and reducing the wavelength redshift.

[0027] Finally, BGaN layer 10 is introduced in V-pit 7, by controlling the molar content of B atoms to be 5%–50%, to significantly increase the band gap and improve the resistivity of BGaN layer 10, further promoting more holes to migrate to the long-wave quantum well on the N side at room temperature, to reduce the difference in WLD at room temperature and hot state, and reduce the wavelength redshift.

[0028] The technical scheme of the existing conventional full-spectrum LED epitaxial wafer manufacturing method is as follows: Step one: desorption treatment is performed on the sapphire substrate; Step two: a buffer layer is grown on the sapphire substrate, the buffer layer being one of AlN and GaN; Step three: a non-doped GaN layer and a Si-doped N-type GaN layer are grown on the buffer layer; Step four: a blending layer is grown on the Si-doped N-type GaN layer, the blending layer being alternating growth of low-In component InGaN well layer and GaN barrier layer, with alternating cycle number being 3-6 times; Step five: a pre-preparation layer is grown on the blending layer, the pre-preparation layer being alternating growth of high-In component InGaN well layer and GaN barrier layer, with alternating cycle number being 3-6 times; Step six: growing a light-emitting layer on the pre-prepared layer, the light-emitting layer comprising sequentially grown first, second and third quantum well layers, each of which comprises cyclically grown InGaN well layers and barrier layers, the number of cycles being 2-8, wherein the first quantum well layer has a peak wavelength of 457-470 nm, the second quantum well layer has a peak wavelength of 445-457 nm, and the third quantum well layer has a peak wavelength of 430-445 nm, and the barrier layers in the first, second and third quantum well layers are AlGaN / GaN superlattice structures or GaN barrier layers.

[0029] Step seven: growing a P-type Mg-doped GaN layer on the light-emitting layer, the Mg doping concentration being between 8E+19 and 3E+20.

[0030] Step eight: growing an AlGaN electron blocking layer, the Al component being from high to low in the growth direction.

[0031] Step nine: growing a lightly Mg-doped GaN layer, the Mg doping concentration being between 1E+19 and 3E+20.

[0032] Step ten: finally growing a heavily Mg-doped GaN layer, the Mg doping concentration being between 4E+20 and 9E+20, and thus the gallium nitride epitaxial wafer is completed.

[0033] The detection results of the main wavelength (WLD) and the light efficiency of the full-spectrum LED epitaxial wafer produced according to the traditional technical solution and the technical solution of the application at room temperature 25℃ and 85℃ are shown in Tables 1 and 2: Table 1 WLD test data of the technical solution of the application

[0034] Table 2 WLD test data of the traditional technical solution

[0035] As can be seen from the above two tables, when the temperature changes from 25℃ to 85℃, the wavelength redshift is within 4 nm (average value 3.8 nm) by using the technical solution of the application, while the wavelength redshift basically reaches 8 nm (average value 8.8 nm) by using the traditional technical solution, the application can significantly reduce the wavelength redshift of the full-spectrum LED under heat, the reduction being more than 50%, the difference between the main wavelength at room temperature and under heat is reduced, and the effect is obvious. At the same time, the V-shaped pit on the application introduces a Fe-doped GaN layer, which significantly improves the light output power and the light efficiency is obviously improved, when the temperature changes from 25℃ to 85℃, the light efficiency decreases within 4 lm / W (average value 3.7), while the light efficiency decreases by more than 12 lm / W (average value 13.2) by using the traditional technical solution.

[0036] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A full spectrum LED epitaxial growth method for reducing wavelength redshift, characterized in that, The method for growing epitaxial material by using a metal organic chemical vapor deposition reaction chamber comprises the following steps: Step one: desorption treatment is performed on a sapphire substrate; Step two: a buffer layer is grown on the sapphire substrate, wherein the buffer layer is AlN or GaN; Step three: a non-doped GaN layer and a Si-doped N-type GaN layer are grown on the buffer layer; Step four: a reconciliation layer is grown on the Si-doped N-type GaN layer; Step five: a pre-preparation layer is grown on the reconciliation layer; Step six: a light-emitting layer is grown on the pre-preparation layer; Step seven: the temperature, pressure, growth speed, gas and metal source flow during the growth of the light-emitting layer are controlled to form a plurality of V-shaped pits in the light-emitting layer by using a dislocation extension mechanism; Step eight: a Fe-doped GaN layer, a Fe and C co-doped GaN layer and a BGaN layer are sequentially grown and filled above the V-shaped pits; Step nine: a Mg-doped P-type GaN layer is grown on the light-emitting layer and the V-shaped pits; Step ten: an AlGaN electron blocking layer is grown, and the Al component is from high to low along the growth direction; Step eleven: a lightly Mg-doped GaN layer is grown; Step twelve: a heavily Mg-doped GaN layer is grown, and the epitaxial wafer is completed.

2. The full spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 1, wherein, In step four, the reconciliation layer is an alternatingly grown low-In component InGaN well layer and GaN barrier layer, and the alternating cycle number is 3-6.

3. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 1, wherein, In step five, the pre-preparation layer is an alternatingly grown high-In component InGaN well layer and GaN barrier layer, and the alternating cycle number is 3-6.

4. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 1, wherein, In step six, the light-emitting layer comprises a first quantum well layer, a second quantum well layer and a third quantum well layer which are sequentially grown, each quantum well layer comprises an InGaN well layer and a barrier layer which are alternately grown in cycles, and the cycle alternating number is 2-8.

5. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 4, wherein, The first quantum well layer has a light-emitting peak wavelength of 457-470 nm, the second quantum well layer has a light-emitting peak wavelength of 445-457 nm, and the third quantum well layer has a light-emitting peak wavelength of 430-445 nm.

6. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 4, wherein, The barrier layer of each quantum well layer is an AlGaN / GaN superlattice structure or a GaN barrier layer, and the relative spectral intensity of blue light of the light-emitting layer under the condition of a wavelength of 450 nm and a color temperature of 4000 K is less than 0.

6.

7. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 1, wherein, In step seven, the V-pit distribution density is 1E8-1E9 cm -2 , and the opening diameter is 220-420 nm.

8. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 1, wherein, In step eight, the Fe source flow is controlled to be 100-150 sccm when the Fe-doped GaN layer is grown, and the layer thickness is 100-200 nm; The Fe source flow was gradually increased from 700 sccm to 900 sccm, and the C doping concentration was 3E17-2E18 cm -3 , and the layer thickness was 100-200 nm.

9. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 1, wherein, In step eight, the molar content of B atoms in the BGaN layer is 5%-50%, and the BGaN layer fills the entire V-shaped pit.

10. The full-spectrum LED epitaxial growth method for reducing wavelength redshift according to claim 1, wherein, In step nine, the Mg doping concentration is 8E+19 - 3E+20 cm -3 ; In step eleven, the Mg doping concentration is 1E+19 - 3E+20 cm -3 ; In step twelve, the Mg doping concentration is 4E+20 - 9E+20 cm -3 .

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