FÍSICA DE SEMICONDUCTORES MOBILIDAD Y CONDUCTIVIDAD EN SEMICONDUCTORES UN Juan Camilo Calvera -fsc06Juan- 2015

MOBILIDAD Y CONDUCTIVIDAD EN EL Si El campo eléctrico provee energía que acelera los electrones en la banda de conducción. Así adquieren grandes velocidades. Debido a la gran cantidad involucrada aparecen las colisiones ó choques entre ellos Aparece la Ley de Ohm y la Conductividad y Movilidad El fenómeno de deriva de portadores además de electrones, en la banda de conducción, también arrastra huecos en la banda de valencia. Así aparece el fenómeno de la Resistencia

MOBILIDAD Y CONDUCTIVIDAD EN EL Si Lea las seccion 3.4.1 y 3.4.2, pag 98 del libro texto, Conductividad y Mobilidad. El tema relaciona el fenómeno de deriva (drift) que arrastra a los electrones debido a su interacción con un campo eléctrico externo. Formule al menos 10 preguntas y escriba su respuesta. Una en cada diapositiva.

Questions 1. Why may the force produced by an electric field be insufficient to alter a single electron? Because a single electron has a random path, on the other hand a group of electrons has no net movement in average. 2. Why do electrons move constantly even at thermal equilibrium? Because of the random scattering produced by lattice vibrations, impurities and other electrons. 3. Why does eq. 3-29 not indicate a continious acceleration? Acceleration from this equation is balanced by deacceleration process produced by collisions.

Questions Which drift is bigger between thermal drift and the one produced by an electric field? The drift speed described by Eq. (3-36), which describes the drift produced by an electric field is usually much smaller than the random speed due to the thermal motion vth. What is current density? It is the number of electrons crossing a unit area per unit time multiplied by the charge of the electron [A/cm^2] What is electron mobility and how does one calculates it? The quantity called the electron mobility, describes the ease with which electrons drift in the material. un=q*t/mn*, where mn* is the effective mass of the electron

Questions 7. What is the effective mass of an electron. 8. What is drift speed? It is the average speed of an electron in a group of electrons, when it is on an electric field 9. What is the chance of a random moving electron to return to it’s initial position? The chance is very low when we consider a single electron, but when we consider a group of electrons there is no net movement. 10. How is mean free time calculated? It is a random constant based on collisions