302+midterm+_2006_

302+midterm+_2006_ - MATSCI 302: Solar Cells Midterm Exam...

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

View Full Document Right Arrow Icon
MATSCI 302: Solar Cells Midterm Exam November 2, 2006 1. The minority carrier lifetime in the bulk (i.e. not near the surface) of a semiconductor grade silicon wafer could in principle be limited by radiative recombination, Auger recombination, or nonradiative recombination via defect states. [5 points for each part] a.) Which recombination mechanism actually limits the carrier lifetime below a doping density of approximately 10 18 cm -3 ? b.) Which mechanism limits the lifetime at higher doping density? Why is recombination by this mechanism so fast at high doping density? c.) Why is the third mechanism [the one that you didn’t select for a.) and b.)] not very important in silicon? 2.) Consider a silicon wafer with a pin junction. The p region has carrier density of 10 16 cm -3 and the n region has a carrier density of 10 19 cm -3 . The doping profile changes very abruptly at the pi and in interfaces. (i stands for intrinsic) [5 points for each part] a.) Draw the charge density versus position. (Line up all drawings below the sketch
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.

This note was uploaded on 12/01/2011 for the course MS&E 302 taught by Professor Mcghee during the Spring '08 term at Stanford.

Page1 / 2

302+midterm+_2006_ - MATSCI 302: Solar Cells Midterm Exam...

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