CN103808497A - Method for measuring quantum efficiency in LED - Google Patents
Method for measuring quantum efficiency in LED Download PDFInfo
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- CN103808497A CN103808497A CN201410079018.5A CN201410079018A CN103808497A CN 103808497 A CN103808497 A CN 103808497A CN 201410079018 A CN201410079018 A CN 201410079018A CN 103808497 A CN103808497 A CN 103808497A
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Abstract
The invention belongs to the technical field of semiconductor illumination LED detection and discloses a method for measuring quantum efficiency in an LED. The method for measuring the quantum efficiency in the LED includes: obtaining LED light emitting efficiency eta LEE according to the geometrical structure of the LED through numerical calculation or software modeling; simply encapsulating an LED chip so as to keep the light emitting efficiency, measuring the change relationship between the LED light power P and the current and the change relationship between spectrum and the current, and calculating to obtain the external quantum efficiency eta EXE of the LED; calculating according to a formula eta EXE=eta IQE eta LEE to obtain the internal quantum efficiency eta IQE of the LED. The method for measuring the quantum efficiency in the LED is simple and reliable and is capable of calculating the internal quantum efficiencies under different currents without complex arithmetical operation.
Description
Technical field
The invention belongs to semiconductor LED photoelectricity test technical field, be specifically related to a kind of method of the LED of measurement internal quantum efficiency.
Background technology
LED is a kind of high efficiency electro-optical conversioning device, and its electro-optical efficiency can use external quantum efficiency (EQE, external quantum efficiency) to characterize, i.e. the ratio of unit interval LED utilizing emitted light subnumber and injected electrons number.And it is long-pending external quantum efficiency further can be decomposed into internal quantum efficiency and light extraction efficiency according to electric light transfer process.Internal quantum efficiency (IQE, internal quantum efficiency) be the ratio that active area produces photon number and injection electron number, light extraction efficiency (LEE, light extraction efficiency) is the ratio that LED utilizing emitted light subnumber and active area produce photon number.Wherein internal quantum efficiency is directly relevant with LED quality, and light extraction efficiency is more to be determined by the geometric configuration of LED chip.
There are now three kinds of methods to measure internal quantum efficiency: (1) is by measuring the photoluminescence intensity under low temperature and room temperature, utilize the internal quantum efficiency under the room temperature that hypothesis that under low temperature, internal quantum efficiency is 100% calculates, this method is too coarse and cannot obtain the internal quantum efficiency with curent change; (2) become exciting power or time-dependent current and then carry out cubic non-linearity matching, this approximating method uncertainty is too large, and fitting parameter is too responsive to surveyed data, and error is unstable very greatly.
Summary of the invention
(1) technical matters that will solve
In view of this, fundamental purpose of the present invention is to provide a kind of simple and reliable method of measuring accurately LED internal quantum efficiency.
(2) technical scheme
For achieving the above object, the invention provides a kind of method of the LED of measurement internal quantum efficiency, the method comprises: according to the geometry of LED, obtain LED light extraction efficiency η by numerical evaluation or software modeling
lEE; LED chip is carried out can not changing to the simplified package of light extraction efficiency, measure LED luminous power P and spectrum with the variation relation of electric current, obtain LED external quantum efficiency η
eXE; And according to formula η
eXE=η
iQEη
lEEcalculate LED internal quantum efficiency η
iQE.
In such scheme, described according to the geometry of LED, obtain LED light extraction efficiency η by numerical evaluation or software modeling
lEE, comprising: if homoepitaxy, whole LED structure has identical specific inductive capacity, utilizes following formula to calculate optical efficiency:
wherein
for the cirtical angle of total reflection, obtain according to Fresnel law
n is the refractive index of LED; If the structure of heteroepitaxy or graph substrate is set up concrete geometric model according to concrete LED geometry in TracePro, utilize ray tracing method to obtain light extraction efficiency.
In such scheme, the described method of utilizing software modeling to calculate optical efficiency, comprising: the LED of plane foreign substrate directly utilizes TracePro software to set up respectively p layer, active layer, n layer and substrate, and corresponding material properties is set; Observation area is set around LED, and the surface properties that observation area receives incident light is made as absorption completely, and active layer upper and lower surface uses Lambertian light source type; The graphic array of graph substrate is set up with relevant CAD software TracePro, is then converted into ascii text file and imports TracePro.
In such scheme, described simplified package of LED chip being carried out can not changing light extraction efficiency, measures LED luminous power P and spectrum with the variation relation of electric current, obtains LED external quantum efficiency η
eXE, comprising: LED chip is encapsulated, when encapsulation, do not affect original light extraction efficiency; Then under different Injection Current I, measure luminous power P and peak wavelength λ; Obtain external quantum efficiency according to the luminous power P and the peak wavelength λ that measure
In such scheme, described LED internal quantum efficiency
(3) beneficial effect
Can find out from technique scheme, the present invention has following beneficial effect:
1, utilize the present invention, due to the internal quantum efficiency that can measure under different electric currents, inject the impact on internal quantum efficiency so can obtain reliable concrete internal quantum efficiency and electric current.
2, utilize the present invention, because testing process has contained radiation recombination, non-radiative compound and electronics leakage mechanisms, so the internal quantum efficiency measuring accurately and reliably.
3, utilize the present invention, owing to not needing complicated mathematical operation, and can detect the LED of any different geometries, so workable, applicability is wide.
Accompanying drawing explanation
Fig. 1 is the method flow diagram of measurement LED internal quantum efficiency provided by the invention.
Fig. 2 is that the LED external quantum efficiency of sapphire plane substrate is with the change curve of electric current.
Fig. 3 is the internal quantum efficiency that the measures change curve with Injection Current.
Fig. 4 is the change curve of sapphire pattern substrate LED external quantum efficiency with Injection Current.
Fig. 5 is the geometric model of the graph substrate LED that sets up in TracePro software.
1-sapphire pattern substrate; 2-n district; 3-active area; 4p district; The complete absorption layer of 5-;
Fig. 6 is the LED internal quantum efficiency that the measures change curve with Injection Current.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, LED internal quantum efficiency measuring method provided by the invention is further described.
As shown in Figure 1, the method for measurement LED internal quantum efficiency provided by the invention, the method comprises the following steps:
Step 1: according to the geometry of LED, obtain LED light extraction efficiency η by numerical evaluation or software modeling
lEE; This step specifically comprises: if homoepitaxy, whole LED structure has identical specific inductive capacity, utilizes following formula to calculate optical efficiency:
wherein
for the cirtical angle of total reflection, obtain according to Fresnel law
n is the refractive index of LED; If the structure of heteroepitaxy or graph substrate is set up concrete geometric model according to concrete LED geometry in TracePro, utilize ray tracing method to obtain light extraction efficiency.Wherein, the described method of utilizing software modeling to calculate optical efficiency, comprising: the LED of plane foreign substrate directly utilizes TracePro software to set up respectively p layer, active layer, n layer and substrate, and corresponding material properties is set; Observation area is set around LED, and the surface properties that observation area receives incident light is made as absorption completely, and active layer upper and lower surface uses Lambertian light source type; The graphic array of graph substrate is set up with relevant CAD software TracePro, is then converted into ascii text file and imports TracePro.
Step 2: LED chip is carried out can not changing to the simplified package of light extraction efficiency, measure LED luminous power P and spectrum with the variation relation of electric current, obtain LED external quantum efficiency η
eXE; This step specifically comprises: LED chip is encapsulated, do not affect original light extraction efficiency when encapsulation; Then under different Injection Current I, measure luminous power P and peak wavelength λ; Obtain external quantum efficiency according to the luminous power P and the peak wavelength λ that measure
Step 3: according to formula η
eXE=η
iQEη
lEEcalculate LED internal quantum efficiency η
iQE; Wherein, described LED internal quantum efficiency
Embodiment 1: the LED internal quantum efficiency that is grown in sapphire plane substrate is measured.
Step 1: set up corresponding model according to actual LED geometry and optical parametric in software, carrying out ray tracing, to obtain light extraction efficiency be η
lEE=27.81%.
Step 2: packaged LED measurement luminous power and spectrum are with the variation of electric current, and curent change scope is 0 to 1200mA, and spectrum peak is 450nm.
Step 3: according to formula
calculate external quantum efficiency, its with curent change situation as Fig. 2.
Step 4: calculate internal quantum efficiency by light extraction efficiency and external quantum efficiency, its with curent change situation as Fig. 3.
Embodiment 2: calculate the internal quantum efficiency that is grown in the LED on sapphire pattern substrate.
Step 1: set up LED model in software, corresponding parameter is set, specifically as shown in Figure 4, then carry out ray tracing, obtaining light extraction efficiency is 75.8%.
Step 2: the luminous power of measurement LED and spectrum are with the variation of electric current, and curent change scope is 0 to 1200mA, and spectrum peak is 450nm.
Step 3: according to formula
calculate external quantum efficiency, its with curent change situation as Fig. 5.
Step 4: calculate internal quantum efficiency by light extraction efficiency and external quantum efficiency, it with curent change situation as shown in Figure 6.
Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of making, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (5)
1. a method of measuring LED internal quantum efficiency, is characterized in that, the method comprises:
According to the geometry of LED, obtain LED light extraction efficiency η by numerical evaluation or software modeling
lEE;
LED chip is carried out can not changing to the simplified package of light extraction efficiency, measure LED luminous power P and spectrum with the variation relation of electric current, obtain LED external quantum efficiency η
eXE; And
According to formula η
eXE=η
iQEη
lEEcalculate LED internal quantum efficiency η
iQE.
2. the method for measurement LED internal quantum efficiency according to claim 1, is characterized in that, described according to the geometry of LED, obtains LED light extraction efficiency η by numerical evaluation or software modeling
lEE, comprising:
If homoepitaxy, whole LED structure has identical specific inductive capacity, utilizes following formula to calculate optical efficiency:
wherein
for the cirtical angle of total reflection, obtain according to Fresnel law
n is the refractive index of LED;
If the structure of heteroepitaxy or graph substrate is set up concrete geometric model according to concrete LED geometry in TracePro, utilize ray tracing method to obtain light extraction efficiency.
3. the method for measurement LED internal quantum efficiency according to claim 2, is characterized in that, the described method of utilizing software modeling to calculate optical efficiency, comprising:
The LED of plane foreign substrate directly utilizes TracePro software to set up respectively p layer, active layer, n layer and substrate, and corresponding material properties is set; Observation area is set around LED, and the surface properties that observation area receives incident light is made as absorption completely, and active layer upper and lower surface uses Lambertian light source type;
The graphic array of graph substrate is set up with relevant CAD software TracePro, is then converted into ascii text file and imports TracePro.
4. the method for measurement LED internal quantum efficiency according to claim 1, is characterized in that, described simplified package of LED chip being carried out can not changing light extraction efficiency is measured LED luminous power P and spectrum with the variation relation of electric current, obtains LED external quantum efficiency η
eXE, comprising:
LED chip is encapsulated, when encapsulation, do not affect original light extraction efficiency; Then under different Injection Current I, measure luminous power P and peak wavelength λ; Obtain external quantum efficiency according to the luminous power P and the peak wavelength λ that measure
5. the method for measurement LED internal quantum efficiency according to claim 1, is characterized in that described LED internal quantum efficiency
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| CN104062575A (en) * | 2014-06-30 | 2014-09-24 | 中国科学院上海微系统与信息技术研究所 | Method for measuring internal quantum efficiency and internal loss of laser |
| CN107228710A (en) * | 2017-05-26 | 2017-10-03 | 厦门大学 | A kind of quantum efficiency of LED measurement apparatus and its measuring method |
| CN113125111A (en) * | 2021-04-10 | 2021-07-16 | 中国科学院新疆理化技术研究所 | External quantum efficiency testing method for vertical cavity surface emitting laser |
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| CN107228710B (en) * | 2017-05-26 | 2018-08-07 | 厦门大学 | A kind of quantum efficiency of LED measuring device and its measurement method |
| CN113125111A (en) * | 2021-04-10 | 2021-07-16 | 中国科学院新疆理化技术研究所 | External quantum efficiency testing method for vertical cavity surface emitting laser |
| CN113125111B (en) * | 2021-04-10 | 2023-03-28 | 中国科学院新疆理化技术研究所 | External quantum efficiency testing method for vertical cavity surface emitting laser |
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Application publication date: 20140521 |