22.3 Photodiodes
619
(a)
10
0
10
10
10
10
-1
-2
-3
-4
10
-5
0
1000
1500
500
0
0.9
0.99
0.999
0.9999
Efficiency
Si
(b)
-2V
-7V
-12V
s (V)
0
-5
-10
Fig. 22.40 a Efficiency of charge transfer with (solid line) and without (dashed line) the effect of the fringing field.
b Schematic plot of the CCD electrodes and bias with the fringing field for a three-electrode CCD, oxide thickness
200 nm, doping N D = 10 15 cm −3 . The electrode pitch is 4 µ m and the gap between electrodes is 200 nm wide. Adapted
from [1854]
Fig. 22.41 Creation of a
lateral potential well
(barrier) in a MIS structure
with a varying doping via
diffusion or implantation
and b varying (stepped)
oxide thickness. Upper row
shows schematic geometry,
lower row depicts
schematic lateral variation
of the surface potential
N' A >N A
V
s
N A
(a)
s
V
N A
(b)
metal
insulator
semiconductor
thick
depletion
region
light
silicon
substrate
transfer
electrode
signal
charge
channel
stopping
diffusion
(a)
(b)
(c)
(d)
Fig. 22.42 a Schematic image of channel isolation. Cross section for channel isolation by b variation of oxide thickness,
c highly doped region and d field effect. Adapted from [1855]