SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

228 CHAPTER 5. SEMICONDUCTOR JUNCTIONS

p-n DIODE SCHOTTK Y DIODE

R everse current is very low

Forward current due to minority

carrier injection from n- and p-sides

S wi tchi ng speed contr ol l ed by

recombination (elimination) of

minority injected carriers

Ideality factor in I-V characteristics

~ 1.2-2.0 due to recombination in

depl eti on r egi on

R everse current is relatively large

D ev i ce v er y f ast: swi tchi ng speed

control l ed by thermal i z ati on of

“ hot” i nj ected el ectrons across the

barrier ~ few picoseconds

Forward current due to majority

i nj ecti on f rom the semi conductor

E ssentially no recombination in

depl eti on r egi on i deal i ty f actor

~ 1.0

F orward bi as needed to mak e the T he cut-in voltage is quite small

dev i ce conducti ng ( the cut- i n

voltage) is large

Figure 5.6: A comparison of some pros and cons of thep-ndiode and the Schottky diode.

barrier is also quite large, which is a disadvantage for many applications. Another issue is
technology related. The Schottky barrier quality depends critically on the surface quality, the
processing steps are quite critical. For many semiconductors, it is not possible to have a good
Schottky contact since the contact is very “leaky” due to defects. For such materials, the only
way to have rectification is by using ap-njunction.