Ion-beam processing effects on the thermal conductivity of n-GaN/sapphire (0001)

We have measured high spatial/depth resolution (2–3 μm) thermal conductivity (κ) at 300 K before and after plasma-induced effects on two series of n-GaN sapphire (0001) samples fabricated by hydride vapor phase epitaxy using scanning thermal microscopy. The sample thicknesses were 50±5 μm for one set and 25±5 μm for the second. The carrier concentrations were ∼8×1016 cm−3 and ∼1.5×1017 cm−3, respectively, as determined by Hall effect measurements. The thermal conductivity before treatment was similar to that previously reported for hydride vapor phase epitaxy material with comparable carrier concentration and thickness [D. I. Florescu et al., J. Appl. Phys. 88, 3295 (2000)]. Damage was induced by ion-beam processing the samples under constant Ar+ gas flow and pressure for a fixed period of time (5 min), with the dc bias voltage (Vdc) being the only variable processing parameter (125–500 V). The thermal conductivity near the surface, κ, was found to exhibit a linear decrease with Vdc in the investigated ra...

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