Terahertz Radiators Based on Silicon Carbide Avalanche Transit …
25
2 Substance Parameters and Design Strategy
The electric field (ξ ) dependences of ionization rate (α n,p ) and drift velocity (v n,p ) of
electrons and holes in Si, 3C-SiC, and diamond are expressed as
α n, p (ξ ) = A n, p exp
−
B n, p
ξ
and v n, p (ξ ) = v sn,sp
1 − exp
−
μ n, p ξ
v sn,sp
(1)
where A n,p , B n,p are of ionization coefficients, and v sn , v sp are saturation drift velocities
of electrons and holes, respectively. Important material parameters of Si, 3C-SiC,
and diamond have been drawn from various published reports [25–31].
Operating frequency of IMPATT device depends upon carrier transit time (τ T ).
Double-drift region (DDR) IMPATT diode having n
+ -n-p-p
+ structure, initially
designed for a definite frequency (f d ) from the transit time formula, is focused by Sze
et al. [32]. Then, the design parameters are optimized via the large-signal simulation
technique based on NSVE model [33]. The design parameters of Si, 3C-SiC, and
diamond are listed in Table 1.
Table 1 Design parameters
Base
material
Design
frequency,
f d (GHz)
n-layer
thickness,
W n (nm)
p-layer
thickness,
W p (nm)
n-layer
doping
concentration,
N D (×10 23
m −3 )
p-layer
doping
concentration,
N A (×10 23
m −3 )
n + - and
p + -layer
doping
concentrations,
N Sub (×10 26
m −3 )
Si
94
400.0
380.0
1.20
1.25
1.00
140
280.0
245.0
1.80
2.10
1.00
220
180.0
160.0
3.95
4.59
1.00
300
132.0
112.0
6.00
7.30
1.00
500
72.0
70.0
15.0
16.2
1.00
3C-SiC
94
410.0
410.0
2.50
2.50
1.00
140
300.0
300.0
5.00
5.00
1.00
220
200.0
200.0
8.00
8.00
1.00
300
160.0
160.0
11.00
11.00
1.00
500
103.0
103.0
16.50
16.50
1.00
1000
57.0
57.0
23.50
22.50
1.00
Type-IIb
diamond
94
780.0
780.0
0.460
0.530
1.00
140
530.0
530.0
0.810
0.870
1.00
220
320.0
320.0
1.350
1.490
1.00
300
220.0
220.0
2.050
2.220
1.00
500
120.0
120.0
3.750
4.100
1.00
1000
52.0
52.0
9.500
10.00
1.00
1500
30.0
30.0
36.00
37.00
1.00
25
2 Substance Parameters and Design Strategy
The electric field (ξ ) dependences of ionization rate (α n,p ) and drift velocity (v n,p ) of
electrons and holes in Si, 3C-SiC, and diamond are expressed as
α n, p (ξ ) = A n, p exp
−
B n, p
ξ
and v n, p (ξ ) = v sn,sp
1 − exp
−
μ n, p ξ
v sn,sp
(1)
where A n,p , B n,p are of ionization coefficients, and v sn , v sp are saturation drift velocities
of electrons and holes, respectively. Important material parameters of Si, 3C-SiC,
and diamond have been drawn from various published reports [25–31].
Operating frequency of IMPATT device depends upon carrier transit time (τ T ).
Double-drift region (DDR) IMPATT diode having n
+ -n-p-p
+ structure, initially
designed for a definite frequency (f d ) from the transit time formula, is focused by Sze
et al. [32]. Then, the design parameters are optimized via the large-signal simulation
technique based on NSVE model [33]. The design parameters of Si, 3C-SiC, and
diamond are listed in Table 1.
Table 1 Design parameters
Base
material
Design
frequency,
f d (GHz)
n-layer
thickness,
W n (nm)
p-layer
thickness,
W p (nm)
n-layer
doping
concentration,
N D (×10 23
m −3 )
p-layer
doping
concentration,
N A (×10 23
m −3 )
n + - and
p + -layer
doping
concentrations,
N Sub (×10 26
m −3 )
Si
94
400.0
380.0
1.20
1.25
1.00
140
280.0
245.0
1.80
2.10
1.00
220
180.0
160.0
3.95
4.59
1.00
300
132.0
112.0
6.00
7.30
1.00
500
72.0
70.0
15.0
16.2
1.00
3C-SiC
94
410.0
410.0
2.50
2.50
1.00
140
300.0
300.0
5.00
5.00
1.00
220
200.0
200.0
8.00
8.00
1.00
300
160.0
160.0
11.00
11.00
1.00
500
103.0
103.0
16.50
16.50
1.00
1000
57.0
57.0
23.50
22.50
1.00
Type-IIb
diamond
94
780.0
780.0
0.460
0.530
1.00
140
530.0
530.0
0.810
0.870
1.00
220
320.0
320.0
1.350
1.490
1.00
300
220.0
220.0
2.050
2.220
1.00
500
120.0
120.0
3.750
4.100
1.00
1000
52.0
52.0
9.500
10.00
1.00
1500
30.0
30.0
36.00
37.00
1.00