Influence of N2/H2 and N2 plasma on binary III-nitride films prepared by hollow-cathode plasma-assisted atomic layer deposition

Abstract

The authors reported the hollow-cathode plasma-assisted atomic layer deposition of AlN, GaN, and InN films using N2-only and N2/H2 plasma. In this study, the authors analyzed the effect of plasma gas composition on the properties of deposited binary III-nitride thin films. Toward this goal, AlN, GaN, and InN films were deposited on Si (100) substrates using N2-only (50 sccm), as well as N2/H2 (50 + 50, 50 + 25 sccm) plasma to investigate the impact of H2 flow. Grazing-incidence x-ray diffraction (GIXRD) patterns of AlN and GaN thin films deposited with N2/H2 plasma remained almost unchanged when H2 flow decreased from 50 to 25 sccm. On the other hand, the use of N2 plasma without any H2 resulted in amorphous GaN thin films with significant carbon impurity within the bulk film. In the case of AlN, similar behavior was observed as the crystal structure is significantly altered to amorphouslike material. Thicknesses of AlN and GaN thin films increased tremendously when N2-only was used as the plasma gas. Furthermore, refractive index values of both AlN and GaN films decreased upon the use of N2-only plasma, which confirm the deterioration of the film quality. Structural weaknesses of GaN and AlN films deposited with N2-only plasma are due to presences of carbon impurities that are trapped inside the growing film. Interestingly, the authors did not observe similar results in InN films grown with N2/H2 plasma. For InN, GIXRD and spectroscopic ellipsometry results show that the phases of deposited films change from InN to In+InN as H2 content in the plasma gas is increased. On the other hand, InN films grown with N2-only plasma show improved structural properties. However, significantly higher N2 plasma exposure times are needed to minimize the residual carbon content in deposited InN layers.

Thermal Atomic Layer Deposition of Polycrystalline Gallium Nitride

“…For poly-GaN ALD (further referred to as GaN ALD), organometallic (e.g., trimethylgallium (TMG) or triethylgallium (TEG)) or halide-based inorganic Ga precursors (e.g., GaCl 3 ) have been used, often utilizing NH 3 or N 2 -H 2 as a nitrogen source. ,− The challenge of ALD by purely thermal means (i.e., without using additional activation techniques) is the activation of the nitrogen precursor, which is chemically very stable. Thermal ALD of GaN from GaCl 3 and NH 3 has been reported to occur at temperatures exceeding 400 °C. − The halide precursor however exhibits several drawbacks, such as difficulty in delivery due to its low vapor pressure (demanding supply- and gas-line heating), etching of the reactor walls from corrosive by-products (e.g., HCl), and Cl incorporation in the growing film .…”

Elucidating the role of nitrogen plasma composition in the low-temperature self-limiting growth of indium nitride thin films

“…35,38 The lower BE peak at 396.5 eV is assigned to nitrogen in the form of InN. 23,31,32,[35][36][37][38][39][40][41][43][44][45][46][47][48][49][50][51][52][53] For Ar/N 2 -plasma samples, the additional components are at 397.2 and 398.3 eV. The upper component is preserved aer sputtering into the bulk of the lm and can be assigned to an In-N-O bonding environment, which leaves the middle component unassigned.…”

“…33,34 To date, there have been multiple efforts towards low-temperature InN growth via PE-ALD. 17,[30][31][32][35][36][37][38][39][40][41] Initial epitaxial growth of InN at sub-300 C was achieved by plasma-enhanced atomic layer epitaxy (PE-ALE) where the lms exhibited substrate-dependent varying crystallographic orientations. 17,36 In a relatively recent study, PE-ALD of monocrystalline InN lms has also been reported at 250 C using N 2 -plasma on lower-lattice-mismatched ZnO/Al 2 O 3 substrates, where the lms were fully relaxed with no voids or interlayers at the interfaces.…”

“…Majority of the studies around PE-ALD deposition of InN report on single-phase h-InN lms when using hydrogen-free nitrogen plasmas, whereas addition of H 2 to the plasma gas has resulted in degraded lm quality with elevated impurity content and even lm porosity. [30][31][32]35,37 Although there have been a number of studies on the plasma-assisted ALD of InN employing N 2 /H 2 and/or N 2 -only plasma compositions, an in-depth investigation of the surface reactions taking place during individual PE-ALD cycles is still signicantly missing. [30][31][32][33][34][35][36][37][38][39][40][41] In this work, we particularly investigate the role of hydrogen radicals in the surface reactions of TMI with Ar/N 2 plasma in a custom-designed compact hollowcathode plasma-ALD reactor.…”

Recent Advances in Hollow Cathode Technology for Plasma-Enhanced ALD—Plasma Surface Modifications for Aluminum and Stainless-Steel Cathodes

“…GaN (PE-ALD) [1,8,10,11,13,14,16,20,21,30,35] GaN devices (PE-ALD) [2,4,10,11,17] Nanofibers (PE-ALD) [5,[9][10][11]] Nanostructures (ALD) [18,21] AlGaN (PE-ALD) [1,3] AlN (PE-ALD) [1,5,[19][20][21]29,32] BN (PE-ALD) [5,6,11] InN (PE-ALD) [10,11,15,[19][20][21]33,34] BInN and BGaN (PE-ALD)…”