The temperature dependence performance of ultraviolet radiation
detectors
T. V. Blank, Yu. A. Goldberg, O. V. Konstantinov
Ioffe Physico-Technical Instituteof Russian Academy of Science,
St. Petersburg, Russia
IWORID 2002 AMSTERDAM
• The temperature dependence of the quantum efficiency of GaP Schottky photodetectors.
• The fluctuation traps model.• Comparison of the temperature dependencies of the quantum
efficiency in Schottky and p-n photodetectors based on GaAs.• The temperature dependence of the quantum efficiency of Si
Schottky photodetectors.• The temperature dependence of the quantum efficiency of 4H-SiC
Schottky photodetectors.• Conclusion.
Outline
Determination of• photoelectric conversion process mechanism in Schottky
photodetectors• temperature stability of UV detectors
Aim
where - quantum efficiency I - photocurrent Р - incident light power h - photon energy q - electron charge
qPIh
Experimental procedure
Electrical heater
Thermopair
Quartzwindows
Light
Researchingphotodetector
Metallic holder
Liquidnitrogen
+
-
R
Researching photodetector
100 150 200 250 300 350
0,05
0,10
0,15
0,20
0,25
0,30 h = 2.83 eV h = 3.40 eV h = 3.98 eV h = 4.91 eV
, el
ectr
on/p
hoto
n
T, K2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5
0,00
0,05
0,10
0,15
0,20
0,25
0,30
h, eV
, el
ectro
n/ph
oton
20 mm
The temperature dependence of the quantum efficiency of GaP Schottky photodetectors
The spectrum of the quantum efficiency of GaP Schottky photodetectors at 300 K.
The quantum efficiency of GaP Schottky photodetectors as a function of the temperature for several photon energies.
Au
In
h
n-GaP250m
1017cm-3
Optical losses
Temperature, К Dielectric
constant of GaP, /0
105 10.88
297 11.02
300 11.1
,2
1
1
R
where R is reflection coefficient is dielectric constant
Bulk losses
3,0 3,5 4,0 4,5 5,0 5,5100
101
102 w
L
nm
h, eV
Others losses
• surface recombination• thermionic emission of thermalized
and hot photoelectrons in the metal
The effective optical length L of GaP as a function of the photon energy, 300 K, W is the width of the space-change region.
=(1-R)(1-hot)(1-thеrm)
1-thеrm=е-/kT
=1=(1-R)(1-hot)е-/kT,
where - quantum efficiency,R - reflection coefficient - internal quantum yieldhot - loss factor of hot
photocarriersthеrm - loss factor of thermalized
photocarriers - activation energy of the
localized photocarriersk - Boltzmann’s constantТ - temperature
The fluctuation traps model
a
Ec
Ev
e
c
Ec
Ev
e
h
Ec
Evd
e
h
h
Ec
Ev
b
Е = 0
Е 0
Schottky and p-n photodetectors based on GaAs
1,0 1,5 2,0 2,5 3,0 3,5 4,00,0
0,2
0,4
0,6
0,8
1,0
h, eV
, el
ectr
on/p
hoto
n
h
p-AlGaAs 0,05m
p+-GaAs
p-GaAs 0,4-0,7m 5·1018cm-3
n-GaAs 1,0-4,0m1·1015 -2·1017cm-3
n-AlAs/GaAs BR, 12 periods
n-GaAs substrate 2·1018cm-3
0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,50,00
0,05
0,10
0,15
0,20
, el
ectr
on/p
hoto
n
h, eVThe spectrum of the quantum efficiency
of GaAs p-n photodetectors at 300 K.The spectrum of the quantum efficiency of GaAs Schottky photodetectors at 300 K.
Ni
n-GaAs 10m 21015cm-3
n+-GaAs 200m 1017cm-3
In
h
Comparison of the temperature dependencies of the quantum efficiency in Schottky and p-n
photodetectors based on GaAs
50 100 150 200 250 300 3500,00
0,05
0,10
0,15
0,20
0,25
T, K
, el
ectr
on/p
hoto
n
h = 1.33 eV h = 1.36 eV h = 1.42 eV h = 1.54 eV h = 1.77 eV h = 1.80 eV h = 4.11 eV h =4.68 eV
50 100 150 200 250 300 3500,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
h = 1.36eV h = 1.42eV h = 1.54eV h = 1.77eV h = 3.00eV
0,000
0,005
0,010
0,015
0,020
Т, К
, el
ectro
n/ph
oton
The quantum efficiency of GaAs p-n photodetectors as a function of the temperature for several photon energies.
The quantum efficiency of GaAs Schottky photodetectors as a function of the temperature for several photon energies.
The temperature dependence of the quantum efficiency of p-n photodetectors
based on Si
1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,50,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
, e
l e c
t r o
n /
p h
o t o
n
h, eV50 100 150 200 250 300 350
0,0
0,1
0,2
0,3
0,4
0,5
0,6
h = 1.11 eV h = 1.25 eV h = 1.33 eV h = 1.40 eV h = 2.00 eV h = 6.04 eV
, e l e
c t r
o n
/ p
h o
t o n
Т, К
The spectrum of the quantum efficiency of Si p-n photodetectors at 300 K
The quantum efficiency of Si p-n photodetectors as a function of the temperature for several photon energies.
3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25
0.00
0.05
0.10
0.15
0.20
0.25
0.30
h, eV
0
20
40
60
80
100
Rel
ativ
e ef
fect
iven
ess,
%
, e
lect
ron/
phot
on
2
1
4H-SiC Schottky photodetectors
The spectrum of the quantum efficiency of 4H-SiC Schottky photodetectors at 300 K (line 1) and the spectrum of the relative effectiveness of different photon energies in bactericidal ultraviolet radiation (line 2).
Cr
n-4H-SiC 25m 41015cm-3
4H-SiC 1019cm-3
Cr
h
75 100 125 150 175 200 225 250 275 300 325 350 375
0.000
0.025
0.050
0.075
0.100
0.125
0.150
0.175
0.200
T , K
, e
lect
ron/
phot
on
4.4eV
4.2eV
4.0eV
3.4eV
50 75 100 125 150 175 200 225 250 275 300 325 350 375
0.258
0.260
0.262
0.264
0.266
0.268
0.270
0.272
0.274
5.01eV
4.91eV
T , K
, el
ectro
n/ph
oto
nThe temperature dependence of the quantum efficiency of 4H-SiC Schottky photodetectors
At 300K W=0.3 mLh~1.4 mLth=Wo+Lh1.7 m=L
-1h~4.5 eV where L is effective optical absorption lengthLth is threshold effective optical absorption lengthW is width of the space-change regionLh is hole diffusion length is absorption coefficient
Short-wave photoeffect
L W+Lh h>4.5 eV
Long-wave photoeffect
L W+Lh h<4.5 eV
Г М
0
3
2
1
5
4
D 1
I 2
D 2
I 1
-1
E c
k
E v
Temperature, К Diffusion length of
holes 4H-SiC, m
80 0.5
400 1.5
The photoelectric conversion mechanism in 4H-SiC Schottky photodetectors
Band structure of 4H-SiC and scheme of different optical transitions.
• For Schottky photodetectors (based on GaAs, GaP, 4H-SiC) the quantum efficiency increases with temperature for all photon energies.
• For p-n photodetectors based on GaAs and Si the quantum efficiency is temperature independent in the region of intrinsic absorption.
• Near-surface imperfections manifest themselves as the fluctuation traps and have an influence on the photoelectric conversion process in Schottky photodetectors.
Conclusion
Future• The temperature dependence of the quantum efficiency of p-n
and Schottky photodetectors based on GaN.• The temperature dependence of the quantum efficiency of not
deep p-n photodetectors (based on 4H-SiC).• External electric field Influence on the quantum efficiency for
UV photodetectors.