The question says:

Calculate the minority carrier life-time in Si having a donor concentration, NA = 1014 cm-3 if the diffusion length for minority carriers is 150 m.

Shouldnt it say "ND=1014"? because its a donor concentration and not an acceptor concentration?


  • \$\begingroup\$ I'm more curious about the 150m diffusion length \$\endgroup\$
    – Dr Coconut
    Commented Feb 4, 2016 at 8:07

1 Answer 1


There's often lots of typos in books. I noticed plenty in my semiconductor book as well. It's frustrating as heck. You might want to confirm these typos with the professor. If enough people (hopefully professors) let the author know about the error, they'll get fixed in the next versions of the book.

But yes, \$ N_D \$ = donor concentration, \$ N_A \$ = acceptor concentration.

  • 1
    \$\begingroup\$ So I was right in this case? Yeah I hate it when they get it wrong because it makes me sooooooooooo confused until I realise theyve put the wrong thing. A 5 min question can take me an hour to do when they mess up the question. \$\endgroup\$
    – Physicsman
    Commented Jan 18, 2016 at 0:29
  • 1
    \$\begingroup\$ @Physicsman Yup, I've wasted half a day on problems when a professor or the author made a typo. You're def right in this case. \$\endgroup\$
    – horta
    Commented Jan 18, 2016 at 0:30
  • \$\begingroup\$ Thanks. Sorry it may seem obvious to you or to people who know what they're doing but I'm just learning this stuff \$\endgroup\$
    – Physicsman
    Commented Jan 18, 2016 at 0:36

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