A silicon junction is doped at and

PHYSICS · Multi-part · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Semiconductor physics and devices · Semiconductor physics and devices

Condensed Matter Physics, Ch The junction: diodes, transistors, lamps and solar cells

Problem

A silicon junction is doped at

N_a=4.0\times10^{17}\,\mathrm{cm^{-3}}

and

N_d=1.0\times10^{17}\,\mathrm{cm^{-3}}

, with

n_i=1.0\times10^{10}\,\mathrm{cm^{-3}}

. ((a)) In one or two sentences, say why the charge density

\rho_q

across this junction is drawn as two rectangular slabs, the field

E_x

as two straight ramps meeting at a single peak, and the potential as two parabolic arcs, rather than any other shape. ((b)) Find the built-in voltage

V_{\rm bi}

, the total width

W_d

, and how that width splits between

x_n

and

x_p

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