4.4. REAL DIODES:DEFECTS AND CARRIER GENERATION 171
forward bias of 0.6 V, the diffusion current is 1. 07 × 10 −^4 A, while the
generation-recombination current is 8. 45 × 10 −^7 A.
Example 4.3Consider a longp-ndiode on silicon with the following parameters:
n-side doping =10^17 cm−^3
p-side doping =10^17 cm−^3
Minority carrier lifetimeτn = τp=10−^7 s
Electron diffusion constant = 30 cm^2 /s
Hole diffusion constant = 10 cm^2 /s
Diode area = 10−^4 cm^2
Carrier lifetime in the depletion region = 10−^8 s
Calculate the diode current at a forward bias of 0.5 V and 0.6 V at 300 K. What is the
ideality factor of the diode in this range?
For this diode structure we have the following:
np =2. 25 × 103 cm−^3
pn =2. 25 × 103 cm−^3
Ln =17. 32 μm
Lp =10. 0 μm
Vbi =0.817V
The prefactor in the ideal diode equation is
I 0 = eA
(
Dppn
Lp
+
Dnnp
Ln
)
=9. 83 × 10 −^16
The prefactor to the recombination-generation current is
IGR^0 =
eAni
2 τ
·
πkBT
eE(0)
whereτis the lifetime in the depletion region.
TheE(0) at a forward bias of 0.5 V is found to be
E(0) = 6. 94 × 104 V/cm
TheE(0) at a forward bias of 0.6 V is found to be
E(0) = 5. 74 × 104 V/cm
