OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 1

Influence of the photo- and X-ray excitation intensity on the

conductivity and luminescence of ZnSe

Kyiv National Taras Shevchenko University, Physics Department

Glushkova ave., 2, k.1, Kyiv 03022

A.O. Sofiienko, V.Ya. Degoda

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 2

• Experimental investigation of the photo- and X-ray

conductivity and luminescence of ZnSe at different

levels of the X-ray excitation.

The purpose of the work

• The estimation of the fundamental differences

between the physical processes in the

semiconductors at the detection of the photo- and

X-ray photons.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 3

• Charge transport in ZnSe semiconductor and its

evaluation as a detector of the ionizing radiation.

Actuality of the work

• The complex research of the conductivity and

luminescence enables to perform more deep

analysis of the kinetics of charge transport, which

is important for its theoretical argumentation.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 4

A schematic of the experimental set-up

h

Sample

Cryostat

γ

PMT

MDR - 2 PMT

X-ray tube

AD - 2 AD - 3

PC

U(V)

AD - 1

i(рA)

UV source (385 nm)

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 5

Fig.1. Measured X-ray luminescence (XRL) and photoluminescence (PL) spectra

of monocrystalline ZnSe at the temperature of 90K.

400 500 600 700 800 900 1000 1100

0

400

800

1200

1600

2000

2400

I()

, nm

x10

x25

630 nm

640 nm

970 nm

XRL PL

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 6

Fig. 2. Measured XRL and PL spectra of polycrystalline ZnSe at the

temperature of 90K.

400 500 600 700 800 900 1000 1100

0

1000

2000

3000

4000

5000

PLXRL

I()

x20

, nm

970 nm

630 nm

800 nm

546 nm

453 nm

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 7

4 6 8 10 12 14 16 18 20

100

200

300

400

500

600

IT, mA

XRL(IT)

546 nm970 nm

250

500

750

1000

1250

1500

1750

XRL(IT)

Fig. 3. The dependence of the intensity of X-ray luminescence in spectrum of

polycrystalline ZnSe on the current of X-ray tube at the temperature of 90 K.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 8

100 200 300 400 500 600

300

400

500

600

700

800

900

1000

1100

1200

1300

Id, abs. unit.

PL(Id)

970 nm 630 nm

100

150

200

250

300

350

400

450

500

550

600

PL(Id)

Fig. 4. The dependence of the intensity of photoluminescence in spectrum of

polycrystalline ZnSe on the intensity of UV source at the temperature of 90 K.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 9

200 400 600 800 1000 1200

0

100

200

300

400

500PL(Id) XRL(IT)

Id, abs. units.

640 nm

0 5 10 15 20 25 30

0

500

1000

1500

2000

2500

IT, mA

630 nm

Fig. 5. The Dependencies of the intensities of photoluminescence in spectrum of

monocrystalline ZnSe on the intensity of UV source (red) and on the current of X-ray

tube (blue) at the temperature of 90 K.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 10

0 50 100 150 200

0

20

40

60

80

100

90 K300 K

U, V

0

50

100

150

200

250

300

j(U), nA j(U), nA

Fig. 6. Volt-ampere characteristics of the X-ray induced conductivity (XRC) of the

monocrystalline ZnSe at different ambient temperatures.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 11

Fig. 7. Volt-ampere characteristics of the photo induced conductivity (PC) of

monocrystalline ZnSe at different ambient temperatures.

0 50 100 150 200

0

500

1000

1500

2000

90 K300 K

U, V

j(U), pA

0

20

40

60

80

j(U), nA

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 12

200 400 600 800 1000 1200

0

50

100

150

200

250

300

350

400

Id, arb. un.

j(U), nA150 V

100 V

50 V

Fig. 8. Lux-ampere characteristics of the monocrystalline ZnSe

at the temperature of 90 K (photoexcitation).

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 13

200 400 600 800 1000 1200

0

10

20

30

40

50

60

j(U), nA

Id, arb. un.

150 V

100 V

50 V

Fig. 9. Lux-ampere characteristics of the monocrystalline ZnSe

at the temperature of 300 К (photoexcitation).

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 14

Fig. 10 Lux-ampere characteristics of the monocrystalline ZnSe

at the temperature of 300 К (X-ray excitation).

4 6 8 10 12 14 16 18 20 22

200

400

600

800

1000

1200

1400

j(U), pA

IT, mA

150 V

100 V

50 V

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 15

200 400 600 800 1000 1200

0

100

200

300

400

500

600

j(U), nA

Id, arb. un.

150 V

100 V

50 V

Fig. 11. Lux-ampere characteristics of the polycrystalline ZnSe

at the temperature of 90 K (photoexcitation).

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 16

Conclusions

1.The comparison of the spectra of photo- and X-ray-

induced luminescence of ZnSe poly- and

monocrystals shows that their intensities have linear

dependence on the excitation intensities of the used

X-ray source and UV photodiodes, and only at small

excitation levels some non-linearity is observed.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 17

Conclusions

2. The functional dependencies of the luminescence

intensity of ZnSe on the excitation level are identical

at Photo- and X-ray excitations. It indicates the

similarity of the kinetics processes of charge carrier

recombination in both cases.

OMEE-2007 A.O. Sofiienko, V.Ya. Degoda 18

Conclusions

3.The investigation of the lux-ampere characteristics of

ZnSe shows that there is a dependence between the

temperature of ZnSe samples and the linearity in

functional dependence between conductivity current

and excitation level. We observed smaller

nonlinearity for ZnSe polycrystals at the temperature

of 90 K.