Influence of ion implantation on structural and photoconductive properties of Bridgman grown GaSe single crystals

Abstract

The structure and temperature dependent spectral photoconductivity of as-grown and N-and Si-implanted GaSe single crystals have been studied. It was observed that post-annealing results in a complete recovery of the crystalline nature that was moderately reduced upon implantation. The band edge is shifted in the implanted sample which is attributed to the structural modifications and continuous shallow levels introduced upon implantation and annealing. Our calculations showed that the trap density is increased upon implantation and annealing which confirms a possibility of explanation the phenomenon within a framework of continuous trap levels. Photocurrent measurements as a function of photo-excitation intensity also support continuous distribution of localized states in the band gap.

Structural, electrical and optical properties of Ge implanted GaSe single crystals grown by Bridgman technique

“…The same behavior was also observed in previous study [23]. Moreover, the XRD patterns of the sample Ge-implanted and annealed at 500°C given in figure 3 indicate that after annealing process the peak intensities are increasing which confirms the evidence of improvement of crystallinity in the same sample as observed for N-and Si-implanted GaSe single crystals [18]. In order to investigate the general behavior of the conductivity and determine the current conduction mechanism, the temperature dependent conductivity measurement was performed in the temperature range of 100-400 K. As seen from figure 4, the variation of conductivity with temperature shows exponential behavior, in the high temperature region above 260 K. Below this point, the conductivity value is almost temperature insensitive.…”

“…This analysis is in good agreement with XRD results. A similar behavior was reported for InSe thin films, in which the optical band gap increasing with annealing was attributed to the selenium segregation at high temperatures as well as the formation of different phases [18,36,37]. For Ge-implanted GaSe samples, the observed increase in optical band gap with annealing might be due to a decrease in the disorder and defect density in the structure.…”

“…Thus, by using this technique, the target material can be doped with a wide range of atomic species at desired concentration. Recently, we carried out structural, electrical and optical characterization on N-and Si-implanted GaSe crystals grown in our laboratory [18][19][20]. During the implantation process because of high energies of accelerated ions, the structure can be disordered.…”

Photoluminescence spectra of nitrogen implanted GaSe crystals

“…Three samples were obtained from this layer. A Varian DF4 type ion implantation system was used for nitrogen implantation [8,9]. One of the samples was not intentionally implanted while the other two samples were implanted by bombarding the crystal surfaces perpendicular to c-axis with ion beams of 60 and 100 keV of doses 10 14 and 10 16 ions/cm 2 , respectively.…”

“…The defects caused by ion implantation were observed to decrease after annealing. Also, the conductivity of crystals implanted with different atoms was dependent on the type of atom [8,9].…”