Electro-Optics - Applied Optics Fundamentals and Device Applications - page 18

- +

p + n i n +

(a)

x

(b)

-

E E v

+

x

(c)

Θ= wt

0 π 2π 3π 4π

(d)

= π

Injected

External

Θ

0 π 2π 3π 4π

(e)

FIGURE 2.10
Read diode (a) p-n-#-n structure, (b) field at avalanche breakdown, (c) energy-band diagram, (d)
AC voltage, and (e) injected and external currents (After Bhasin, K.P. et al., Monolithic optical inte-
grated control circuitry for GaAs MMIC-based phased arrays, Proc. SPIE 578, September, 1985.).

more free carriers. As long as the bias voltage across the diode is larger than
the breakdown voltage, avalanche breakdown occurs; therefore, the maxi-
mum amount of avalanche current occurs at the time just before the bias dips
below the breakdown voltage. This is referred to as the injection phase delay.
The injection phase delay must be present for the IMPATT diode to exhibit
negative resistance. This can be seen by looking at Figure 2.11 which is a plot
of AC resistance at three different injection phase delays. Note that when there