Investigation of Microplasma Breakdown in 4H Silicon Carbide
- PDF / 1,632,673 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 34 Downloads / 147 Views
Abstract Reverse bias breakdown behaviour of high quality 4H silicon carbide p-n diodes was investigated, using optical and electrical measurement techniques. Most of the sample diodes suffered from early breakdown phenomena in the form of microplasmas at about 80% of the calculated parallel plane breakdown voltage for the diodes, as evident from measured I-V curves. A group of these microplasmas could be correlated to micropipes, identified by optical microscopy, while a large number of microplasmas were caused by other defects and inhomogenities in the space charge region under reverse bias. The same spots that revealed early breakdown phenomena under reverse bias also showed a different electroluminescence (EL) behaviour under low forward current densities compared to those areas with a homogeneous breakdown behaviour. However, even diodes containing one or more micropipes in the region of the junction showed good rectifying behaviour up to two third of the parallel plane breakdown voltage, where the turn-on of a microplasma was observed.
Introduction It has been shown that silicon carbide (SiC) has excellent physical properties as a semiconductor for high frequency and high power electronic devices [1, 2]. However, the commercial fabrication of those devices still suffers from insufficient quality of available substrates and epitaxial layers. While the density of micropipes (hollow tubes, related to screw dislocations with Burgers vector >2c) in the available substrates has been drastically reduced, there still remains a large amount of other defects in the substrates and epitaxial layers [3]. These defects show a strong influence on the electric properties of devices, such as early breakdown phenomena and inhomogeneous current distribution under both forward and reverse bias [4, 5, 6]. The early breakdown most often occurs in the form of microplasmas, which are localized spots of high current density in the reverse biased junction. These phenomena were first described by D. J. Rose more than 40 years ago in reverse biased silicon junctions
[7]. A microplasma is caused by a local inhomogenity in the avalanche multiplication factor, leading to a locally increased generation of carriers in the reverse biased junction. In a bias range of a few volts above the turn-on of a microplasma, typical current instabilities are observed, which consist of current pulses with a certain amplitude. In silicon junctions a slight increase of the pulse amplitude with the applied bias was observed [8]. At increasing 151 Mat. Res. Soc. Symp. Proc. Vol. 512 ©1998 Materials Research Society
.'
E C.
1010"L
1
10
>"
10
10.;'0i .
)
10
80
C:
D (D
>
S10-t1 -
. 81
82
, ,
,
83
84
85
.
4-
..
10
. --. ..
., .
diodK0
10 10,7
diode K02
diode K02
.
diode K07 -------diode K16
10" 1 0 g"
20
30
40
50
60
70
80
90
100
110
120
130
reverse bias [V] Figure 1: Reverse biased I-V characteristicsof some typical 4H-SiC diodes. Sample diode K05 (solid line and inset) shows a typical microplasma turn-on at a re
Data Loading...
