A study on the growth and characteristics of $AgGaS_2$ single crystal thin film by hot wall epitaxy

HWE 방법에 의한 $AgGaS_2$단결정 박막성장과 특성에 관한 연구

  • Published : 1998.04.01

Abstract

The stochiometric composition of $AgGaS_2$polycrystal source materials for the single crystal thin films were prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns, it was found that the polycrystal $AgGaS_2$has tetragonal structure of which lattice constant $a_0\;and \;c_0$ were 5.756 $\AA$ and 10.305 $\AA$, respectively. $AgGaS_2$single crystal thin film was deposited on throughly etched GaAs(100) substrate from mixed crystal $AgGaS_2$by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about 0.5 $mu \textrm{m}$/h. The crystallinity of the grown single crystal thin films was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2$single crystal thin films at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by${\Alpha};=;8.695{\times}10^{-4};eV/K,and;{\beta};=;332;K$. from the photocurrent spectra by illumination of polarized light of the $AgGaS_2$single crystal thin film, we have found that crystal field splitting $\Delta$Cr was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

수평 전기로에서 $AgGaS_2$ 다결정을 합성하여 HWE 방법으로 $AgGaS_2$ 단결정 박막을 성장하였다. $AgGaS_2$ 단결정 박막을 성잘할 때 증발원과 기판의 온도를 각각 $590^{\circ}C$, $440^{\circ}C$로 성장하였을 때 이중결정 X-선 요동곡선(double crystal X-ray diffraction rocking curve, DCRC)의 반폭치(FWHM)값이 124 arcsec로 가장 작아 최적 성장조건이었다. 상온에서 $AgGaS_2$ 단결정 박막의 광흡수 특성으로부터 에너지 띠간격이 2.61cV였다. Band edge에 해당하는 광전도도 peak의 온도 의존성은 Varshni 관계식으로 설명되었으며, Vaeshni 관계식의 상수값은 Eg(0) = 2.7284eV, $\alpha$= 8.695$\times$10-4 eV/K, $\beta$= 332K 로 주어졌다. 광발광 봉우리는 20K에서 414.3nm(2.9926eV)와 414.1nm(2.7249eV)는 free exciton(Ex)의 upper polariton과 lower polariton인 {{{{{E}`_{x} ^{u} }}}}와 {{{{{E}`_{x} ^{L} }}}}, 423.6nm(2.9269eV)는 bound exciton emission에 의한 I로 관측되었다. 또한 455nm(2.7249eV)의 peak는 donor-acceptor pair(DAP)에 기인하는 광발광 봉우리로 관측되었다.

Keywords

References

  1. Appl. Phys. Lett. v.25 S.Wagner;J.L. Shay;P. Migliorato;H.M. Kasper
  2. J. Appl. Phys. v.56 I. Shih;A. Vahid Shahidi;C.H. Champness
  3. J. Elec. Mate. v.4 P. Migliorato;J.L. Shay;H.M. Kasper
  4. 13th. IEEE Photovoltaic Specialistic Conf. Record (IEEE, Princeton 1978) L.L. Kazmerski;P.J. Ireland;F.R. White;R.B. Cooper
  5. J. Vac. Sci. Technol. v.B2 no.4 I.W.F. Russel;B.N. Baron;R.E. Rocheleau
  6. Opt. Commun. v.8 D.C. Hanna;V.V. Rampel;R.C. Smith
  7. Appl. Phys. Lett. v.31 W. Jantz;P. Koidi
  8. Appl. Phys. Lett. v.29 R.J. Seymour;F. Zernike
  9. Mat. Sci. Eng. v.5 J.C. Bergman;S. Kurtz
  10. Phys. Rev. v.B6 B. Tell;H.M. Kasper
  11. J. Appl. Phys. v.45 P.W. Yu;Y.S. Park
  12. Appl. Phys. Lett. v.26 H. Matthes;R. Viehman;N. Marschell
  13. J. Appl. Phys. v.45 P.W. Yu;J. Manthuruthil;Y.S. Park
  14. J. Appl. Phys. v.4 H.A. Chedzey;D.J. Marshall;H.J. Pakfitt;D.S. Robertson
  15. J. Crystal Growth v.24 no.125 P. Korczak;C.B. Staff
  16. J. Vac. Sc. Technol. v.15 A. Smith
  17. J. Appl. Phys v.69 J. Arias;M. Zandman;J.G. Pasko;S.H. Shin;L.D. Bubulac;R.E. Dewanes;W.E. Tennart
  18. Thin Solids Films v.10 K.K. Muravyeva;I.P.K. Kinm;V.B. Aleakvsky;I.N. Anikin
  19. Thin Soild Films v.9 J.T. Calow;D.L. Kirr;S.J.T. Owen
  20. Thin Solid Films v.8 J.E. Genthe;R.E. Aldrich
  21. Elements of X-ray Diffractions B.D. Cullity
  22. Optical Process in Semi-conductors J.I. Pankove
  23. Z. Physik v.3 B. Gudden;R. Pohl
  24. Z. Physik v.5 B. Gudden;R. Pohl
  25. Photoconductivity of Solids R.H. Bube
  26. Physica v.34 Y.P. Varshni
  27. IEE, J. Quantum Electronics v.QE-7 G.D. Boyd;H. Kasper;J.H. Mcfee
  28. Phys. v.B4 B. Tev;H.M. Kasper
  29. Solid State Comun. v.13 P.W. Yu;W.J. Auderson;Y.S. Park