Week12HWSolutions

Ece656 7 fall 2013 mark lundstrom 103013 5d

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Unformatted text preview: Fall 2013 Mark Lundstrom 10/30/13 nS Bz I 0.5 ! 200 ! 10"6 = = = 2.92 ! 1016 cm -2 rH qVH 1.6 ! 10"19 21.4 ! 10"3 ( ) nS rH 2.92 ! 1016 cm -2 = nH = = 5.62 ! 1017 cm -3 t 0.0520 cm nH = n = 5.62 ! 1017 cm -3 rH Not the carrier concentration, but the “Hall carrier concentration.” 5b) What is the mobility? Solution: 195 ! 10"3 Rxx = = 975 # 200 ! 10"6 L Rxx = ! S = 975 " W W 1.70 1 ! S = 975 " = # 975 = 625 = L 2.65 nS qµ n 1 1 µn = = 16 nS q ! S rH " 2.92 " 10 " 1.6 " 10#19 " 625 1 rH µ n = µ H = = 0.3 cm 2 /V-s 16 "19 2.92 ! 10 ! 1.6 ! 10 ! 625 µ H = 0.3 cm 2 /V-s Not the mobility, but the “Hall mobility.” ECE ­656 7 Fall 2013 Mark Lundstrom 10/30/13 5d) If the scattering time is 1ps, find the magnetic field for which this classical analysis of Hall effect is no longer valid? Solution: We require: ! c" << 1 qBz ! << 1 m* q! µ n = * m m*µ n != q (i) (ii) With (ii), (i) becomes qBz m*µ n << 1 ! Bz µ n << 1 m* q Using the Hall mobility as an estimate of the real mobility Bz µ n = 0.5 ! 0.3 = 0.15 << 1 so this experiment is in the low B ­field regime. The largest the B ­field can be to be in the low field regime is Bz = 1 1 = = 3.33 T µ n 0.3 Bz = 3.33 T 6) Contact resistances are important. They can complicate measurements of semiconductor transport parameters, and they can degrade device performance. The constant resistance is specified by the interfacial contact resistivity, !C ,...
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