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Effect of annealing temperature on optical and electrical properties of nitrogen implanted p-type ZnMgO thin films

  • SAHA, S
  • NAGAR, S
Publication Date
Jan 01, 2015
DSpace at IIT Bombay
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p-type nitrogen doped Zn1-xMgxO (x = 0.15) thin films were prepared on n-type silicon substrates by RF sputtering. Plasma-immersion-ion technique and rapid-thermal process were used to implant nitrogen and annealing (700-1000 A degrees C) of these films respectively. Annealed samples at 700, 800, 900 and 1000 A degrees C showed effective improvement of the structural and optical properties. X-ray diffraction spectra showed improvement in < 002 > orientation of films with increase in annealing temperatures. In Raman spectra, the peak at 436 cm(-1) corresponds to E (2) (high) phonons mode of ZnMgO wurtzite structure and FWHM of this peak decreases with increase in annealing temperature, indicating improvement in crystalline quality. The scanning electron microscopy results demonstrate that nitrogen-implanted ZnMgO film annealed at 1000 A degrees C has better morphology in comparison to other films. Low-temperature (15 K) photoluminescence measurements revealed acceptor-bound exciton peak at 3.45 eV and donor-bound exciton peak around 3.52 eV. Increased intensity of acceptor-bound exciton peak with increasing annealing temperature proves that nitrogen implantation and subsequent annealing increase the acceptor concentration in the film, indicating tendency for p-type conduction at higher annealing temperature. The film annealed at 1000 A degrees C was observed to produce only acceptor-bound exciton emission and no donor-bound exciton emission was occurred. Hall-effect measurements showed p-type conductivity for annealed films in temperature range at 800-1000 A degrees C. The acceptor level at 3.45 eV in PL spectra is responsible for this p-type conduction in these films. The highest hole concentration of 1.91 x 10(15) cm(-3) has been achieved for film annealed at 1000 degrees C.

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