ECE4904 Semiconductor Devices B2014 ECE4904 Semiconductor Devices B2014 Problem Set 3 Due at beginning of class, Tuesday, November 18. Be sure your ECE mailbox number is visible on the front of your problem set! 1) 5.1(c,d,e,g,h) p. 227 [Quick questions] EXPLAIN YOUR ANSWERS! If "true", give an example. If "false", explain why and what the correct statement would be. 2) 5.2 p. 228 [Diode energy band diagram] 3) 5.4 p. 228 [Diode electrostatics] 4) 5.8 p. 230 [Qualitative diode electrostatics] Just a sketch is required here, no equations. Be sure to indicate the shape of the various parts of your sketch – for example, linear, quadratic, cubic, etc. 5) 5.10 p. 231 [Diode with not-quite-step junction] 6) 5.11 p. 231 [PIN diode] The PIN diode is widely used as a photodiode in high speed optical communication applications. The electric field in the I (intrinsic) region helps to rapidly separate hole-epairs that are created by incident photons. MORE ON THE NEXT PAGE!!! 1 ECE4904 7) Semiconductor Devices B2014 [Nonuniformly doped region] For a certain region of nonuniformly doped semiconductor material in equilibrium at T=300K, it is known that the mobile electron concentration n(x) in the region 0 < x < 0.01cm is given by the expression n ( x ) = [1.0E +14 cm 3 ] e( −x 0.00175cm) This expression is plotted (on a log scale) on the top axes on the next page. € axes as n(x), plot the hole concentration p(x) a) Using the same b) Using the space indicated, carefully plot the energy band diagram. Be sure to indicate numerical values for EF relative to Ei at x=0 and x=0.01cm. c) Sketch the electrostatic potential (voltage) V. Use the potential at x=0 as your zero reference. Be sure to indicate a numerical value for the voltage at x=0.01cm. d) Sketch the electric field as a function of position x. Be sure to indicate a numerical value for the electric field at x=0.01cm. To make life easier on yourself (and the grader), print out a copy of the plot and do your plots directly on the copy. Be sure to show your work on a separate sheet of paper. 2 (b) ENERGY BAND DIAGRAM (c) ELECTROSTATIC POTENTIAL (d) CARRIER CONCENTRATIONS (a) ELECTRIC FIELD ECE4904 Semiconductor Devices 3 B2014 V x 0.01cm ε x 0.01cm ECE4904 Semiconductor Devices 4 B2014