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The pn Junction University of Delaware(pn结特拉华大学).pdf

发布:2017-09-02约1.89万字共32页下载文档
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The p-n Junction ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner The pn Junction • The pn Junction in Equilibrium – Built in voltage – Carrier concentrations – Depletion Region • The pn Junction Under Bias – Carrier Injection • IV equation for pn junction – Minority carrier current in quasi-neutral regions – Current flow in depletion region – Physical Meaning of I0 – Reverse breakdown • Quasi-Fermi Levels • Non-idealities – Series resistance – High Injection – Depletion Region Recombination ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner pn Junction in Equilibrium • Bring p type and n type material together physically • Thermal equilibrium means no extra heat, no applied voltages, no light • The electrons from the n type material will diffuse into the p type material (and vice versa for holes) • After crossing the junction the electrons in the p type (holes in n type) material are minority carriers with a recombination lifetime • Keep in mind the dopant atoms don’t move – they are part of the crystal ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner pn Junction in Equilibrium • Movement of carriers across junction leaves ionized dopant atoms behind • Material is now charged since the balancing charge carrier is gone • Electric field is now present around the junction • Region around the junction is called the space charge region or more commonly the depletion region (since the region surrounding the junction is depleted of carriers) Note: remember Electric field direction
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