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.