(Open triangles) c-RBS measured in the axial direction from -implanted GaAs samples as implanted ( at 20 keV) and (open circles) after laser melting using (90 ns) followed by RTA at for 10 s in 1 atm of . For comparison, the channeled and the random spectra from an unimplanted GaAs (001) substrate are shown by solid lines.
SIMS depth profile of nitrogen concentration for as-implanted ( at 20 keV, solid circles) and samples. The PLM was performed at 0.27 (open squares, “low fluence”) and (open triangles, “high fluence”), resulting in melt durations of 65 and 99 ns, respectively. Both laser melted samples were treated by RTA at for 5 s in 1 atm of . 1D diffusion simulated profiles are shown as dashed and dashed dotted lines with best-fit parameters given in Table I. The arrows indicate the values of assigned to the samples, which are the averaged concentrations within the calculated melt depths given in Table I.
(a) SD-BEEM spectra for different nitrogen concentrations. The spectra are vertically offset arbitrarily for clarity. The topmost dotted line represents the SD spectrum of the unprocessed GaAs substrate without implantation. (b) Composition dependence of thresholds observed at the peaks of the SD-BEEM spectra of . The open symbols are the thresholds for LT-MBE grown (Ref. 9), and the solid symbols are for the thresholds for II-PLM-RTA measured in this work. The lines are linear fits of the concentration dependence for MBE grown (dotted) and II-PLM (solid) samples.
(a) A series of room temperature PR spectra measured for the -implanted GaAs after PLM and RTA at for 5 s in 1 atm of . The arrows indicate the position of the lowered subband by fitting. The bandgap energies from the fitting of PR spectra are plotted vs nitrogen concentration in (b). The dashed line is the calculated bandgap energies based on the BAC model.
Comparison of bandgap energies from PR measurement and the Schottky barrier heights from BEEM measurement. The spectra are vertically offset arbitrarily for clarity. The dashed line is the calculated bandgap energy based on the BAC model.
STM and BEEM images of one of the implanted dots. Both images are measured simultaneously at and . The Au grains and -implanted dot ( diameter in the center) are visible in the STM image, and an enhancement of the BEEM current is observed at the implanted region. The sample was implanted with of at 20 keV, followed by of PLM and RTA at for 10 s. The section profile below each image was measured along the dashed lines and smoothed to show the trend more clearly.
BEEM spectra on and off the synthesized dot imaged in Fig. 6, exhibiting shift in thresholds on the dot at tip bias below the Schottky barrier height of unimplanted surrounding GaAs. The arrows indicate best-fit BEEM thresholds for on dot (0.84 V) and off dot (0.93 V). The sample was implanted with of at 20 keV, followed by of PLM and RTA at for 10 s.
1D diffusion simulation parameters for fitting final nitrogen-concentration depth profiles for low and high fluence samples.
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