Question

11)

Briefly describe the photoluminescence (PL) and electroluminescence (EL) phenomena

Answer 1

The term Luminescence basically means formation or emission of light as a consequence of output which is based on the nature of excitement.

(1). Photoluminescene : Optical radiation (which is the input or source of excitation) and Light as the source of output.

(2). Electroluminescene : Electric Field or Current (which is source of excitation) and Light as the source of output.

Photoluminescence term which is mainly used in spectroscopy, generally referred to as PL, is the phenomenon in which light energy, or photons, cause the emission of a photon from virtually from any matter.  It is basically a non-contact, nondestructive technique of probing materials. The basic principle lies in the fact that , light is being directed onto a sample, which is then absorbed and then a process called photo-excitation will occur. consecutively , the photo-excitation will cause the material to go to a higher energy electronic state, and it will then subsequently release energy, (photons) since it relaxes and comes back to a ground state energy level. The emission of light or luminescence from this process is referred to as photoluminescence, PL. PL mapping basically combines traditional PL with mainly a scanning stage. therefore Both the intensity and the peak wavelength get uniformity across the whole wafer can hence be obtained which is then used for evaluation.

Electroluminescence is the phenonomenon in which the emission of photons takes place mainly in the presence of an electric field or current. EL displays and light sources were mainly common 30 to 50 years ago in the form of night lights and as displays which is used in automobiles. They were basically formed of zinc sulfide which is doped with copper or silver. With the introduction of of LEDs EL displays ran out of race primarily because of their low efficiency and short life time .Electroluminescence is mainly performed on the devices like LEDs because it needs a device framework structure to inject current.