56 10 cm 8 jb p250 diffusion current density of holes

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Unformatted text preview: ivity 1 1.56 10 Ω ∙ cm 8 J&B P2.50 Diffusion current density of holes is The concentration profile for holes is 10 10 cm Then 10 At 0, diffusion current density is 1.2 10 A/cm 0 1.2 10 A/cm Diffusion current is 0 0∙ 1.2 10 A 7 J&B P2.52 Note that the positive direction is to the right, and the direction of the electric field is to the left, thus 20 V/cm. (The signs of , , , are very important in this exercise!) The concentration profiles are linear, thus the gradients of concentrations are ∆ ∆ 5 10 cm ∆ ∆ 5 10 cm 350 cm / V ∙ s , Mobilities of electrons and holes are From Einstein’s relationship 150 cm / V ∙ s . The diffusivities of electrons and holes are (assuming room temperature, 25.9 ) 9.1 cm /s 3.9 cm /s At 0, 10 cm , 1.01 10 cm Electron diffusion current density: 72 A/cm Hole diffusion current density: 31 A/cm Electron drift current density: 11.2 A/cm Hole drift current density: 4.85 10 A/cm Total current density: 5.4 1 m (mid-point) Since the profiles are linear, at 10 10 2 1.01 10 2 10 A/cm 5 10 10 cm 1.005 10 cm Electron and hole diffusion currents are the same as derived above: 72 A/cm 31 A/cm Electron drift current density: 5.6 A/cm Hole drift current density: 4.8 10 A/cm...
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