GB/T 30655-2014Test methods for internal quantum efficiency of nitride LED epitaxial layers (English PDF)

3.1 Radiative recombination

During the transition of electrons from a high-energy state to a low-energy state, a certain amount of energy shall be released when electrons and holes recombine. If the energy is released in the form of photons, this recombination is called radiative recombination.

3.2 Non radiative recombination

During the transition of electrons from a high-energy state to a low-energy state, a certain amount of energy shall be released when electrons and holes recombine. The recombination that releases energy in ways other than photon radiation is called nonradiative recombination.

3.3 Extraction efficiency

The ratio between the number of photons emitted by a light-emitting diode per unit time and the number of photons generated by radiative recombination in the active area.

3.4 External quantum efficiency

The ratio OF the number of photons emitted by the number of injected carriers per unit time TO the number of injected carriers.

3.5 Internal quantum efficiency

Under certain injection conditions, the ratio of the number of photons generated by radiative recombination per unit time to the total number of composite carriers injected per unit time.

3.6 Injection efficiency

The ratio between the number of composite carriers injected into the active area and the total number of injected carriers per unit time under certain injection conditions.

3.7 Exciton

An electron-hole pair that is bound together by the Coulomb interaction.

3.8 Electroluminescence

A physical phenomenon in which a material emits light through electrical injection.

3.9 Photoluminescence

A physical phenomenon in which a material emits light through light stimulation.

9.1 Preparation of test

Before the test, check and make sure that all instruments in the test system are in good conditions.

9.2 Test steps

9.2.1 The steps for testing the internal quantum efficiency by the ratio of the integrated intensity of low-temperature and room-temperature photoluminescence spectra are as follows.

a) Turn on the laser and check whether it works properly;

b) Turn on the power switches of the monochromator and detector in turn and check whether they work properly;

c) Calibrate the monochromator by a standard light source;

d) Install the sample on the sample rack; then install the vacuum protective cover; evacuate the vacuum; start circulating cooling water and compressor; wait until the temperature drops below 20K, and start measuring after stabilizing at this temperature for 30 min;

e) Use the data acquisition system to measure the low-temperature photoluminescence spectrum by dedicated software;

f) Then use resistance heating to raise the temperature to room temperature (295K) and stabilize for 30 min, and continue to use the data acquisition system to measure the room-temperature photoluminescence spectrum by dedicated software;

g) Turn off power supplies of all the instruments after the test is completely finished;

h) Calculate the internal quantum efficiency by software.

9.2.2 The steps for testing the internal quantum efficiency by the integral intensity of the photoluminescence spectrum with constant temperature-variable excitation density are as follows.

a) Turn on the laser and check whether it works properly;

b) Turn on the power switches of the monochromator and detector in turn to check whether they work properly;

c) Calibrate the monochromator with a standard light source; if the room temperature test is used, proceed directly to step e); if the high and low temperature test is used, proceed to step d);

d) Install the sample on the sample rack; then install the vacuum protective cover; evacuate the vacuum; start the circulating cooling water and compressor; wait until the temperature reaches the set temperature, and start the measurement after it stabilizes at this temperature for 30 min;

e) Change the laser excitation density by inserting attenuation plates with different attenuation multiples in the laser optical path; and then use the data acquisition system to measure the photoluminescence spectra under different laser excitation densities by dedicated software;

f) Then restore the temperature to room temperature (295K) through resistance heating or cooling machine; and after stabilizing for 30 min, turn off power supplies of all the instrument;

g) Calculate the internal quantum efficiency by software.

9.2.3 The steps to infer the internal quantum efficiency from the external quantum efficiency by the light extraction model are as follows.

a) Turn on the switches of power supply and detector power in turn to check whether they are working properly;

b) Calibrate the integrating sphere with a standard light source;

c) Install the sample on the sample rack; turn on the power supply to the LED; start measuring the light power of the LED; and calculate the external quantum efficiency by dividing it by the input power (the product of current and voltage); […]