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Spectroscopic studies of laser-irradiated ZnSe crystals
464
ABSTRACTS Nitrogen d o n o r s can also be partially nentmlized during hydrogcm, ion. At present, we did not achieve a neutralization efficiency as high as for tl~ accepto~. We have Ix~enable to neu~dize 75 % of the nitrogen donors in bulk materials. A full reactivation of the donors can be achieved by high temperature annealing in inert atmosphere. We have not beeu able yet to observe any kr,al vibrational mode associated with the hydrogen-shallow dopant complexes; however it has to |~ noled that the investigated samples are quite opaque in the infrared range wheresuchmodc~sare expected. This work therefore shows that hydrogen neutralizes Ihe shallow dopants in silicon carbide as il does in more "classical" scmiconduetorS such as silicon for filslance.
Nitrogen-Hydrogen Complexes in G a P a n d G a A s W.-S. Hahn a, B.Clerjaud a, D. Ctte a, F. Gendron a, C. Porte a, W. Ulrici b, D. Wasik a and W. Wilkening a aUniversit~ Pierre et Marie Curie, Case 86 F-75252 Paris codex 05, France bpaal-Drude-Institat fflr Festktrpcrelcktronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
Vol. 93, No. 5 whole region of doping by REE. T h e spect r a l s - 2 p + of shallow donors in GaAs samples doped by Y b [1] a n d G d [2] in liquid phase, respectively, were observed. T h e R E E doping leads to purification of a crystal from residual i m p u r i t i e s which provides more exact identi- fication of t h e chemical n a t u r e of shallow donors in G a A s , a n d t h e selective int e r a c t i o n of R E E w i t h t h e VI group e l e m e n t s allows i n t e r p r e t a t i o n of " S n / S e " resonance in t e r m s of Se donors. References 1. R u d a y a N.S., B o l k h o v i t y a n o v Yu.B., Zhuravlev K.S., et al., P i s m a Zurn. Tehn. Fiziki 16, 37 (1990). 2. Zhuravlev K.S., Yakusheva N.A., Shamirzaev T.S., et al., Fiz. Tehn. Pol. 27, 1473 (1993).
SPECTROSCOPIC A spectroscopic study of the nitrogen-hydrogen complexes in GaP and GaAs is presented; these complexes are evidenced by the observation of their local vibrational modes. It is shown that these complexes are formed when hydrogen diffuses in the neutral state i.e. when the Fermi level is higher than Ev + 0.3 eV in GaP or Ev + 0.5 eV in GaAs. These complexes involve two hydrogen atoms both directly bonded to the nitrogen atom. It is shown that in GaP, the complex can exist in three different states. Two of these states correspond to different charge states of the complex; it is not definitely established yet whether the third state corresponds to a third charge state or to a metastable state of one of the two charge states. Therefore, the complex is electrically active. The conversions between the three different states by illumination of the samples are described. In GaAs, only two states have been observed: a stable state and a second state which corresponds either to a metastable state or to a second charge state. Experiments under uniaxial stress have been performed on all the local vibrational modes associated with all the states. They allow to determine the microscopic structures of most states of the complexes. No reodentation of the complexes at room temperature has been observed. MAGNETOSPECTROSCOPY OF S H A L L O W D O N O R S IN G a A s , D O P E D B Y Y b A N D Gd O.A.Shegai K.S.Zhuravlev, T.S.Shamirzaev, N.A.Yakusheva I n s t i t u t e of Semiconductor Physics, 630090 Novosibirsk, Russia
T h e effect of doping by rare e a r t h elem e n t s ( R E E ) Y b a n d G d on t h e electrical properties a n d i m p u r i t i e s s p e c t r u m of pure GaAs, grown by liquid p h a s e epitaxy ( L P E ) from Bi melt, has b e e n investigated. T h i s p a p e r is one of a few works in which, due to a low level of residuM impurities, it was possible to identify residual donors in t h e
STUDIES OF L A S E R IRRIDIATED ZnSeCRYSTALS
Gnatyuk V . A . , Borshch V. V., Dmitryuk S.G.,"Kopishinska O.P.0 "Mozol P.E. Poltava Pedagogical Institute #Institute of Physics of Semiconductors, Kiev, UKRAINE -The photoconductivity (PC), photoluminescence (PL], and Ram a n scattering spectra were stu-
dies in high-resestivity, undoped, cubic ZnSe single c r y s t a l s with different concentrations of accidental impurities, both before and after bombardment with nanosecond ruby laser pulses.The impurity concentrations were determined from EPR s p e c t r a and from certain features of the low temperature PL spectra.The structural perfection of crystals also valued from coefficients of oneand two photon absorption. It was established, that multiple irradiation of ZnSs crystals calls the increase of steadystate PC. The dark conductivity was not affected. The steadystate photosensitization of ZnSe is studied for the first time. It takes place only for samples with low ( ~ 10 xa cm -3) impurity concentrations. Modification of PC spectra, exitonic PL spectra, and the appearance of two additional peaks in the Raman spectra indicates the increase of the concenration of point defects in sensitized crystals.The increase of photosensitivity is explained by the formation of r-centres, which are Zn vacancies counterbalanced by shallow donor centres (pos~bly of interstitial Zn).
ABSTRACTS Nitrogen d o n o r s can also be partially nentmlized during hydrogcm, ion. At present, we did not achieve a neutralization efficiency as high as for tl~ accepto~. We have Ix~enable to neu~dize 75 % of the nitrogen donors in bulk materials. A full reactivation of the donors can be achieved by high temperature annealing in inert atmosphere. We have not beeu able yet to observe any kr,al vibrational mode associated with the hydrogen-shallow dopant complexes; however it has to |~ noled that the investigated samples are quite opaque in the infrared range wheresuchmodc~sare expected. This work therefore shows that hydrogen neutralizes Ihe shallow dopants in silicon carbide as il does in more "classical" scmiconduetorS such as silicon for filslance.
Nitrogen-Hydrogen Complexes in G a P a n d G a A s W.-S. Hahn a, B.Clerjaud a, D. Ctte a, F. Gendron a, C. Porte a, W. Ulrici b, D. Wasik a and W. Wilkening a aUniversit~ Pierre et Marie Curie, Case 86 F-75252 Paris codex 05, France bpaal-Drude-Institat fflr Festktrpcrelcktronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
Vol. 93, No. 5 whole region of doping by REE. T h e spect r a l s - 2 p + of shallow donors in GaAs samples doped by Y b [1] a n d G d [2] in liquid phase, respectively, were observed. T h e R E E doping leads to purification of a crystal from residual i m p u r i t i e s which provides more exact identi- fication of t h e chemical n a t u r e of shallow donors in G a A s , a n d t h e selective int e r a c t i o n of R E E w i t h t h e VI group e l e m e n t s allows i n t e r p r e t a t i o n of " S n / S e " resonance in t e r m s of Se donors. References 1. R u d a y a N.S., B o l k h o v i t y a n o v Yu.B., Zhuravlev K.S., et al., P i s m a Zurn. Tehn. Fiziki 16, 37 (1990). 2. Zhuravlev K.S., Yakusheva N.A., Shamirzaev T.S., et al., Fiz. Tehn. Pol. 27, 1473 (1993).
SPECTROSCOPIC A spectroscopic study of the nitrogen-hydrogen complexes in GaP and GaAs is presented; these complexes are evidenced by the observation of their local vibrational modes. It is shown that these complexes are formed when hydrogen diffuses in the neutral state i.e. when the Fermi level is higher than Ev + 0.3 eV in GaP or Ev + 0.5 eV in GaAs. These complexes involve two hydrogen atoms both directly bonded to the nitrogen atom. It is shown that in GaP, the complex can exist in three different states. Two of these states correspond to different charge states of the complex; it is not definitely established yet whether the third state corresponds to a third charge state or to a metastable state of one of the two charge states. Therefore, the complex is electrically active. The conversions between the three different states by illumination of the samples are described. In GaAs, only two states have been observed: a stable state and a second state which corresponds either to a metastable state or to a second charge state. Experiments under uniaxial stress have been performed on all the local vibrational modes associated with all the states. They allow to determine the microscopic structures of most states of the complexes. No reodentation of the complexes at room temperature has been observed. MAGNETOSPECTROSCOPY OF S H A L L O W D O N O R S IN G a A s , D O P E D B Y Y b A N D Gd O.A.Shegai K.S.Zhuravlev, T.S.Shamirzaev, N.A.Yakusheva I n s t i t u t e of Semiconductor Physics, 630090 Novosibirsk, Russia
T h e effect of doping by rare e a r t h elem e n t s ( R E E ) Y b a n d G d on t h e electrical properties a n d i m p u r i t i e s s p e c t r u m of pure GaAs, grown by liquid p h a s e epitaxy ( L P E ) from Bi melt, has b e e n investigated. T h i s p a p e r is one of a few works in which, due to a low level of residuM impurities, it was possible to identify residual donors in t h e
STUDIES OF L A S E R IRRIDIATED ZnSeCRYSTALS
Gnatyuk V . A . , Borshch V. V., Dmitryuk S.G.,"Kopishinska O.P.0 "Mozol P.E. Poltava Pedagogical Institute #Institute of Physics of Semiconductors, Kiev, UKRAINE -The photoconductivity (PC), photoluminescence (PL], and Ram a n scattering spectra were stu-
dies in high-resestivity, undoped, cubic ZnSe single c r y s t a l s with different concentrations of accidental impurities, both before and after bombardment with nanosecond ruby laser pulses.The impurity concentrations were determined from EPR s p e c t r a and from certain features of the low temperature PL spectra.The structural perfection of crystals also valued from coefficients of oneand two photon absorption. It was established, that multiple irradiation of ZnSs crystals calls the increase of steadystate PC. The dark conductivity was not affected. The steadystate photosensitization of ZnSe is studied for the first time. It takes place only for samples with low ( ~ 10 xa cm -3) impurity concentrations. Modification of PC spectra, exitonic PL spectra, and the appearance of two additional peaks in the Raman spectra indicates the increase of the concenration of point defects in sensitized crystals.The increase of photosensitivity is explained by the formation of r-centres, which are Zn vacancies counterbalanced by shallow donor centres (pos~bly of interstitial Zn).