# hw5_sol - 3.091 Homework#5 page 2 1 Each In atom will...

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

3.091 Homework #5 page 2 1. Each In atom will attract an electron and thus create a “mobile hole”; we only have to determine the number of In atoms/cm 3 . The atomic volume of the host crystal (Ge) is given on your PT as 13.57 cm 3 /mole. (a) # Ge atoms/cm 3 = 23 3 6.02 10 atoms 1 mole 1 mole 13.57 cm × × = 4.44 × 10 22 atoms/cm 3 # In atoms/cm 3 = 4.44 × 10 22 × 0.0003 × 10 -2 = 1.33 × 10 17 In/cm 3 The number of free charge carriers (“holes”) is 1.33 × 10 17 /cm 3 ; they are created through the acquisition of one electron by each In atom from the valence band of the host crystal. (b) conduction band valence band +. . . .+ In . . . . In 1.33 × 10 17 In ions in the band gap just above the valence band edge. 1.33 × 10 17 holes in the valence band E g =0 .7eV acceptor level for In 2. λ crit = hc E g = 6.62 × 10 34 × 3 × 10 8 1.1 × 1.6 × 10 19 = 1.13 × 10 6 m The critical λ for silicon is 1.1 × 10 -6 m; thus radiation of λ = 5 × 10 -7 m = 0.5 × 10 -6 m has even more energy than that required to promote electrons across the band gap.

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 4

hw5_sol - 3.091 Homework#5 page 2 1 Each In atom will...

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

View Full Document
Ask a homework question - tutors are online