SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

314 CHAPTER 7. TEMPORAL RESPONSE OF DIODES AND BIPOLAR TRANSISTORS

+

R

i(t)

v(t)

VR

VF

0

t 1

Time

+

(a)

(b)

i(t)

VF

R

t 1

Time

(c)

t

Current in the diode reaches IF =

Increasing time

EXCESS MINORITY

CHARGE

n-side x

Δpn

0

Minority carrier density builds up on

the n-side as the diode is forward

biased

(d)

Voltage across the diode builds up to

its final value

t 1

Time

t

v(t) V 1 ~kBTn

t< t 1

( )

IF

Io

TURN ON

e

∼2τp

Figure 7.4: Turn-ON characteristics of ap-ndiode: (a) The voltage switches fromVRtoVFas
shown att=t 1. (b) Current response (c) Time evolution of the minority charge injected into the
n-side. (d) Voltage across thep−ndiode.