SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

170 CHAPTER 4. JUNCTIONS IN SEMICONDUCTORS:P-NDIODES

P-contact N-contact

Diode on

dislocated

GaN

Diode on

LEO GaN

p-GaN

n-GaN

SiO 2 mask LEO GaN

Dislocated GaN

2μm GaN

10 -13

10 -12

10 -11

10 -10

10 -9

10 -8

10 -7

-50 -40 -30 -20 -10 0

50

100

150

200

250

10 -6

10 -5

10 -4

10 -3

10 -2

10 -1

Current (A)

Voltage (V)

Temperature (C)

Current Density (A / cm

2 )

(a)

(b)

(c)

(d)

Figure 4.15: Effects of threading dislocations on reverse leakage current inp-ndiodes. GaN
p-ndiodes were fabricated on the same wafer, some of them being placed on areas with high
dislocation density, and some placed in areas with virtually no dislocations. The fabrication
process is shown in (a) - (c). Current characteristics for a number of diodes are shown in (d).
We see that the reverse leakage current in the devices on dislocated material is 3-4 orders of
magnitude higher than that of devices on non-dislocated material, indicating that the dislocations
provide a leakage path for current to travel. Figures taken from the PhD dissertation of Peter
Kozodoy, UCSB.