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LED (Electroluminescence), Structure of LED (PN junction diode) - Coggle…
LED (Electroluminescence)
Manufacturing Process
Epitaxial Growth by MOCVD (Metal Organic Chemical
Vapor Deposition)
Semiconductor Film is Grown by metalorganic vapor
What is CVD
solid coating is formed by gaseous vapor
condition : high temperatre (200 - 2200) in a reaction chamber
Sapphire Function
High thermal conductivity (dissipate heat)
Good Lattice match with GaN to improve the quality of epitaxial layer growth
Electrical Insulation to prevent short circuit
Chemical Stability for manufacturing process that involves the use of harsh chemical
substrate manufacturing process
Czochralski method (growth Al2O3)
More prone to defects
Bigger maximum lattice size
Cylindrical Crystal
Kyropoulos method (growth Al2O3)
Fewer lattice deffect hence lower internal stress
Smaller maximum lattice size
Pear Shaped Crystal
Read about substrate function
Mechanism
E-h pairs called exciton are generated, and excite light (photon)
These excitons are generated by voltage bias
Electron and holes themselves have different mobilities, hence modification such as adding buffer layer to adjust e/h recombination area
How to improve concentration of electron and holes? Doping (p and n type)
How to improve recombination rate (efficiency)
Quantum well
Recombination rate is influenced by every layer of devices
Blue Led (GaN)
Structure of Proposed LED design
p type electrode
p type GaN
InGaN/GaN Quantum Well (for efficiency and spectra control/ in other word acts as an active layer)
Multiple Quantum Well can be added for higher recombination efficiency
n type GaN
Substrate (buffer layer / undoped GaN) to prevent electric arc
0001 Sapphire
p,n type region, active layer, substrate
the positive electrode (p type), the negative electrode (n type) for the holes and electrons to recombine
Structure of LED (PN junction diode)