A silicon - junction is so heavily doped on the side that essentially all the…

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

Solid State Physics, Ch Junctions and devices, finished

Problem

A silicon p+p^+-nn junction is so heavily doped on the pp side that essentially all the depletion capacitance is set by the lightly doped nn side, of unknown doping NDN_D. A measured plot of 1/C21/C^2 against reverse bias VRV_R (with the applied voltage V=−VRV=-V_R) is a straight line, 1C2=a+bVR,\frac{1}{C^2}=a+bV_R, with intercept a=9.0×1014 F−2 cm4a=9.0\times10^{14}\,\mathrm{F^{-2}\,cm^4} (at VR=0V_R=0) and slope b=1.2×1015 F−2 cm4 V−1b=1.2\times10^{15}\,\mathrm{F^{-2}\,cm^4\,V^{-1}}, where CC is the capacitance per unit area. Take εs=11.7\varepsilon_s=11.7 for silicon. ((a)) Find the built-in voltage VbiV_{bi}. ((b)) Find NDN_D.

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