High active nitrogen flux growth of GaN by plasma assisted molecular beam epitaxy

Abstract

In the present study, the authors report on a modified Riber radio frequency (RF) nitrogen plasma source that provides active nitrogen fluxes more than 30 times higher than those commonly used for plasma assisted molecular beam epitaxy (PAMBE) growth of gallium nitride (GaN) and thus a significantly higher growth rate than has been previously reported. GaN films were grown using N2 gas flow rates between 5 and 25 sccm while varying the plasma source's RF forward power from 200 to 600 W. The highest growth rate, and therefore the highest active nitrogen flux, achieved was ∼7.6 μm/h. For optimized growth conditions, the surfaces displayed a clear step-terrace structure with an average RMS roughness (3 × 3 μm) on the order of 1 nm. Secondary ion mass spectroscopy impurity analysis demonstrates oxygen and hydrogen incorporation of 1 × 1016 and ∼5 × 1017, respectively. In addition, the authors have achieved PAMBE growth of GaN at a substrate temperature more than 150 °C greater than our standard Ga rich GaN growth regime and ∼100 °C greater than any previously reported PAMBE growth of GaN. This growth temperature corresponds to GaN decomposition in vacuum of more than 20 nm/min; a regime previously unattainable with conventional nitrogen plasma sources. Arrhenius analysis of the decomposition rate shows that samples with a flux ratio below stoichiometry have an activation energy greater than decomposition of GaN in vacuum while samples grown at or above stoichiometry have decreased activation energy. The activation energy of decomposition for GaN in vacuum was previously determined to be ∼3.1 eV. For a Ga/N flux ratio of ∼1.5, this activation energy was found to be ∼2.8 eV, while for a Ga/N flux ratio of ∼0.5, it was found to be ∼7.9 eV.

Molecular beam epitaxy of free‐standing bulk wurtzite AlxGa1‐xN layers using a highly efficient RF plasma source

“…2 is in excellent agreement with the classical papers on the kinetics of PA-MBE of GaN [9]. The highest growth rate achieved under these growth conditions was 3 µm/h, which is in agreement with the earlier Riber results for that type of the source on thin GaN layers [8]. After establishing of the position of transition from Nrich to Ga-rich growth we have grown a set of wurtzite Al x Ga 1-x N layer under slightly group III-rich conditions with the different thickness and different Al content.…”

“…Previous studies demonstrated that to achieve the highest growth rate of ~7.6 µm/h one needs to use a very high nitrogen flow of ~25 sccm [8]. In order to grow thick Al x Ga 1-x N layers in our conventional MBE system with the standard pumping configuration we used relatively low nitrogen flow rates of ~6 sccm.…”

“…The aperture conductance has been increased by increasing the number of holes, which allows a further increase in the GaN growth rate. Researchers from Santa Barbara have demonstrated that the new source with 5880 holes in the aperture plate allows them to achieve growth rates for thin GaN layers up to 7.6 µm/h with high nitrogen flow rates of about 25 sccm [8].…”

Measurements of nitrogen atom density in a microwave‐excited plasma jet produced under moderate pressures

“…E-mail: jaeho.kim@aist.go.jp *Research Institute for Advanced Electronics and Photonics, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan **GaN Advanced Device Open Innovation Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Aichi, Japan ***Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya, Aichi, Japan ****Faculty of Science and Technology, Meijo University, Nagoya, Aichi, Japan *****Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8564, Japan and a low-temperature growth of silicon nitride films [8]. In addition, nitrogen plasmas have been studied to develop the growth processes of GaN [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], which is a III-nitride semiconductor material with numerous applications in opto-electronic devices such as light emitting diodes, laser diode, and electronic devices based on high-electron-mobility transistors [25,29]. Over the past few decades, plasma-assisted methods such as plasma-assisted metalorganic chemical vapor deposition [9,[12][13][14]16,18,21,23,25], plasma-assisted molecular beam epitaxy [10,11,15,[19][20][21]…”

“…In addition, nitrogen plasmas have been studied to develop the growth processes of GaN [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], which is a III-nitride semiconductor material with numerous applications in opto-electronic devices such as light emitting diodes, laser diode, and electronic devices based on high-electron-mobility transistors [25,29]. Over the past few decades, plasma-assisted methods such as plasma-assisted metalorganic chemical vapor deposition [9,[12][13][14]16,18,21,23,25], plasma-assisted molecular beam epitaxy [10,11,15,[19][20][21][22]26,28], and plasma-assisted atomic layer deposition [24,27] have been studied in regard to the growth of GaN using plasma-activated nitrogen species.…”