VIII.2. A Semiconductor Device Primer

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Using these relationships the net hole current becomes = q Dp dEF p k T dx Accordingly, the net electron current J J Since, individually, the net hole and electron currents in equilibrium must be zero, the derivative of the Fermi level ⇒ in thermal equilibrium the Fermi level must be constant throughout the junction region. For the Fermi level to be flat, the band structure must adapt, since on the p-side the Fermi level is near the valence band, whereas on the n-side it is near the conduction band. If we assume that the dopants are exclusively donors on the n-side and acceptors on the p-side, the difference in the respective Fermi levels is This corresponds to an electric potential p n e dE p dx often referred to as the “built-in” voltage of the junction. B Dn dEF = −qen k T dx ΔE = −k F B B dEF dx = μ = 0 N T log 1 ΔVF = ΔEF ≡ V q Introduction to Radiation Detectors and Electronics Copyright © 1998 by Helmuth Spieler VIII.2.a. A Semiconductor Device Primer, Doping and Diodes p = −μ N A D 2 ni bi n F dE n dx F
As either NA or ND increases relative to ni, the respective Fermi level moves closer to the band edge, increasing the built-in voltage. With increasing doping levels the built-in voltage approaches the equivalent potential of the band-gap Eg /qe. (from Sze) Introduction to Radiation Detectors and Electronics Copyright © 1998 by Helmuth Spieler VIII.2.a. A Semiconductor Device Primer, Doping and Diodes
Page 1 and 2: VIII.2. A Semiconductor Device Prim
Page 3 and 4: The number of occupied electron sta
Page 5 and 6: With these simplifications the numb
Page 7 and 8: 2. Carrier Concentrations in Doped
Page 9 and 10: It is often convenient to refer all
Page 11: Equilibrium is attained when the tw
Page 15 and 16: 4. The Forward-Biased p-n Junction
Page 17 and 18: This yields the solution n p ( x) =
Page 19 and 20: Since the two electron currents mus
Page 21 and 22: Energy band diagrams showing the in
Page 23 and 24: Since the equilibrium concentration
Page 25 and 26: Note that in the diode equation a)
Page 27 and 28: However, on a logarithmic scale it
Page 29: The discrepancies between the measu

VIII.2. A Semiconductor Device Primer

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