Activation of p-Type GaN in a Pure Oxygen Ambient

Abstract

In this study, we activated p-type GaN in a pure oxygen ambient by rapid thermal annealing. The sheet resistance of p-type GaN was greatly reduced from > 10 7 / to 7.06 × 10 4 / after annealing in oxygen ambient at 500 • C. The photoluminescence intensity of blue emission increased by one order of magnitude compared to the as-grown sample. Moreover, the sheet resistance of p-type GaN annealed in pure oxygen ambient is lower than that of p-type GaN annealed in nitrogen ambient. The carrier concentrations of the samples annealed in oxygen ambient are higher than those annealed in nitrogen ambient. The better activation of p-type GaN in oxygen ambient is due to the higher activity of oxygen than that of nitrogen. Oxygen would remove hydrogen that passivates Mg atoms by forming H 2 O at a lower temperature.

The effects of oxygen, nitrogen, and hydrogen annealing on Mg acceptors in GaN as monitored by electron paramagnetic resonance spectroscopy

“…9,25,26 At least two studies show that the conductivity of GaN:Mg films remains approximately the same after annealing at temperatures between 700°C and 1,000°C. [1][2][3]5 Significantly, the resistivity does not increase by an order of magnitude as might be expected from the decreased intensity of the Mg-related acceptor EPR signal. Preliminary Hall measurements on selected samples used for this investigation indicate that the hole density did not change significantly between the 800°C and 1,000°C anneals.…”

“…The temperature dependence of the EPR signal in O 2 versus N 2 reflected the same trend as seen for the hole density. 2,3,23 That is, the studies of Wen and co-workers as well as Hull and co-workers show that the removal of hydrogen from the Mg complex occurs at lower temperatures when the samples are annealed in oxygen rather than nitrogen. 2,3 The sets of data shown in Figs.…”

“…2,3,23 That is, the studies of Wen and co-workers as well as Hull and co-workers show that the removal of hydrogen from the Mg complex occurs at lower temperatures when the samples are annealed in oxygen rather than nitrogen. 2,3 The sets of data shown in Figs. 1 and 2 are consistent with the interpretation of the EPR signal originally identified by Glaser and co-workers and, separately, Palczewska and co-workers as the Mg acceptor.…”

“…Early work showed that Mg-doped GaN grown by chemical vapor deposition (CVD) must be irradiated with low-energy electrons or annealed at temperatures greater than 700°C in either N 2 or O 2 to reduce the resistivity to 1 ohm-cm. [1][2][3] On the other hand, films grown by molecular-beam epitaxy (MBE) exhibit p-type conductivity without any post-growth treatment. 4 The results of secondary-ion mass spectroscopy (SIMS), infrared spectroscopy, and electrical measurements indicate that the acceptors in CVD GaN are rendered inactive by hydrogen, and that annealing in N 2 or O 2 releases hydrogen from a Mgacceptor complex.…”

“…4 The results of secondary-ion mass spectroscopy (SIMS), infrared spectroscopy, and electrical measurements indicate that the acceptors in CVD GaN are rendered inactive by hydrogen, and that annealing in N 2 or O 2 releases hydrogen from a Mgacceptor complex. [1][2][3][5][6][7][8] Annealing is typically performed at a temperature below 850°C because higher temperatures are known to create microscopic defects and trigger nitrogen desorption. 9,10 Theoretical calculations based on infrared spectroscopy data suggest that hydrogen bonds to a nitrogen atom forming a Mg-N-H complex rather than a simple hydrogenmagnesium bond.…”