What Is PL (Photoluminescence)?

What Is PL (Photoluminescence)?

PAM-XIAMEN can supply semiconductor wafers, more wafer specifications please refer to https://www.powerwaywafer.com/products.html. If necessary, we will offer PL (photoluminescence) spectroscopy for the semiconductor wafers.

1. What is PL?

About PL, it refers to the self-emission light produced by a material after being excited by light. When a substance absorbs photons and re-radiates photons, photo luminescence occurs. In quantum mechanics, this process can be described as the transition of substances to an excited state after absorbing photons, and then from a higher-energy excited state to a lower-energy state. During the return process, photons are simultaneously released.

Principle of Photoluminescence

Principle of Photoluminescence

Generally, photoluminescence can be divided into fluorescence and phosphorescence, the delay time of the two is different. Fluorescence refers to the transition from the excited singlet state to the basic radiation transition. The fluorescence lifetime is relatively short, about the order of ps to ns. Phosphorescence is the transition from the excited triplet state to the ground state. Resistance in this process is generally forbidden and has a long lifetime, ranging between us and ms, and is invisible to the naked eye at room temperature and air.

2. What can Photoluminescence Be Used for?

PL is an effective method for detecting discrete energy levels, and photo luminescent can also extract effective information about the semiconductor materials.

1) Composition determination of semiconductor wafers, quantum well thickness, and quantum dot monodispersity measurement. Take the composition determination for example:

GaAs1-xP, is a mixed crystal composed of GaAs with direct band gap and GaP with indirect band gap, and its band gap varies with the value of x. The peak wavelength of luminescence depends on the band gap, which is related to the value of x. Therefore, the component percentage x value can be determined from the peak-to-peak wavelength of the luminescence;

2) Impurity identification: trace impurities in GaAs and GaP can be identified based on the position of characteristic emission lines;

3) Concentration determination of shallow impurities in silicon;

4) Comparison of radiation efficiency:

Semiconductor light-emitting and laser devices require materials with good light-emitting properties, and light-emitting measurement directly reflects the light-emitting properties of materials. By measuring the photoluminous spectrum, not only the intensity of each photoluminescence band gap but also the integrated radiation intensity can be obtained. Under the same measurement conditions, the relative radiation efficiency can be obtained between different samples;

5) Determination of the compensation degree of GaAs material:

Compensation degree NA/ND (ND, NA are donor and acceptor impurity concentrations, respectively) is an important characteristic parameter to characterize the purity of materials;

6) Determination of minority carrier lifetime;

7) Study of uniformity in semiconductor wafers:

The measurement method is to scan the sample with a laser microprobe, and directly display the uneven image of the sample according to the intensity change of a certain characteristic luminescence band of the sample;

8) Research on wafer defects, such as dislocations.

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