hw7_solutions

hw7_solutions - ECE 440 Homework VII Solutions Spring 2008...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
ECE 440 Homework VII Solutions Spring 2008 1. Consider a silicon sample at 300 K. Assume that the difference of hole concentration varies linearly with distance. At x=0, the hole concentration is p(0). At x=10 μm, the hole concentration is p(10 μm)= 5x10 14 /cm 3 . If the hole diffusion coefficient, assumed constant, is D p =14 cm 2 /sec, determine the hole concentration at x=0 for the following two diffusion current densities: (a) the diffusion current density at x=0 is found to be J p diff = + 0.19 A/cm 2 and (b) J p diff = - 0.19 A/cm 2 . The expression for the diffusion current is in 4-22b. We can replace the derivative with the slopes of the hole concentration. 0 f 0 f p diff p x x ) p(x ) p(x qD J - - - = Thus, p 0 f diff p f 0 qD ) x (x J ) p(x ) p(x - + = (a) 3 14 19 3 14 10 85 . 5 ) 14 )( 10 6 . 1 ( 10 19 . 0 10 5 ) 0 ( - - - = + = = cm x x x x x p (b) 3 14 19 3 14 10 15 . 4 ) 14 )( 10 6 . 1 ( 10 19 . 0 10
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 7

hw7_solutions - ECE 440 Homework VII Solutions Spring 2008...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online