Abstract
We report experimental results for the detection of deep-level defects in GaN after Mg ion implantation before high-temperature annealing. The n-type GaN samples were grown on GaN free-standing substrates by metalorganic vapor phase epitaxy. Mg ions were implanted at 50 keV with a small dosage of 1.5×1011 cm-2, which did not change the conduction type of the n-GaN. By depositing Al2O3 and a Ni/Au electrode onto the implanted n-GaN, metal-oxide-semiconductor (MOS) diodes were fabricated and tested. The measured capacitance–voltage (C–V) characteristics showed a particular behavior with a plateau region and a region with an anomalously steep slope. Fitting to the experimental C–V curves by simulation showed the existence of deep-level defects and a reduction of the carrier concentration near the GaN surface. By annealing at 800oC, the density of the deep-level defects was reduced and the carrier concentration partially recovered.
Highlights
Detection of deep-level defects and reduced carrier concentration in Mg-ionimplanted GaN before high-temperature annealing
The successful formation of p-type regions on GaN epitaxial layers on free-standing GaN substrates by Mg ion implantation has been confirmed by observing the rectifying characteristics of p-n junctions formed by applying multicycle rapid thermal annealing,[5,6] standard high-temperature annealing,[7,8] and coimplantation of the N-face of GaN with Mg and H ions.[9]
It has been reported that defects remain in the Mg-implanted GaN layer even after high-temperature annealing on the basis of positron annihilation spectroscopy (PAS) and photoluminescence (PL) studies.[10,11]
Summary
Detection of deep-level defects and reduced carrier concentration in Mg-ionimplanted GaN before high-temperature annealing The results of the C–V measurement at frequencies of 1 kHz – 1 MHz and a bias sweep rate of 50 mV/s for the sample with the as-implanted GaN layer are shown, where an anomalous plateau can be seen, indicating the existence of discrete states in the band gap.
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