A measured silicon p-n junction gives the following forward-bias current density…

PHYSICS · Multi-part · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Electronics, Instrumentation & Communication · Semiconductor devices and analogue circuits

Solid State Physics, Ch Junctions and devices, finished

Problem

A measured silicon p-n junction gives the following forward-bias current density

J

against voltage

V

T=300\,\mathrm{K}

(take

k_BT/e = 25.85\,\mathrm{mV}

): Region A (higher bias):

V=0.500\,\mathrm{V}

J=1.00\times10^{-6}\,\mathrm{A\,cm^{-2}}

;

V=0.619\,\mathrm{V}

J=1.00\times10^{-4}\,\mathrm{A\,cm^{-2}}

. Region B (lower bias):

V=0.200\,\mathrm{V}

J=1.00\times10^{-9}\,\mathrm{A\,cm^{-2}}

;

V=0.319\,\mathrm{V}

J=1.00\times10^{-8}\,\mathrm{A\,cm^{-2}}

. ((a)) Using

J=J_0\,e^{eV/n_{\rm id}k_BT}

, find the ideality factor

n_{\rm id}

in each region. ((b)) Identify the physical mechanism responsible for each region and state which one, extrapolated to

V=0

, gives the diffusion saturation current density

J_0

of the Shockley equation.

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