Growth of twin-free cubic In₂O₃(111) thick layers on c-plane sapphire substrates by halide vapor phase epitaxy

Abstract

The growth of twin-free single-crystal cubic-indium oxide (c-In2O3) layers was investigated by halide vapor phase epitaxy on c-plane sapphire substrates with various off-axis angles. The growth rate of the c-In2O3 layer increased and twin formation was suppressed as the off-axis angle of the substrate was increased. A single-crystal c-In2O3(111) layer grown on a sapphire substrate with a 5° off-axis angle showed a room temperature carrier density and mobility of 1.4 × 1016 cm−3 and 232 cm2 V−1 s−1, respectively. Temperature-dependent Hall measurements of the layer revealed that the mobility is dominated by optical phonon scattering.

Growth of α-In2O3 films with different concentrations of In2O3 powder used as source precursor by mist chemical vapor deposition

“…This is mainly affected by optical phonon scattering as well as nondegenerated c-In 2 O 3 films. 21,31) The highest Hall mobility of 686 cm 2 V −1 s −1 was observed at 100 K. However, this is also influenced by the SEAL. We can expect to obtain better electrical properties, with regard to both carrier concentration and Hall mobility, through the reduction of the SEAL carriers, for example, by using additional oxygen plasma treatment.…”

“…c-In 2 O 3 has been grown using various growth methods, such as pulsed laser deposition, 10) molecular beam epitaxy (MBE), [11][12][13] metalorganic chemical vapor deposition, [14][15][16] melt-growth 17,18) and halide vapor-phase epitaxy (HVPE). [19][20][21] Goto et al reported the superior electrical properties of the lowest carrier concentration of 1.4 × 10 16 cm −3 and the highest Hall mobility of 232 cm 2 V −1 s −1 at room temperature in the as-grown c-In 2 O 3 film by HVPE, 21) in which the bulk region is expected to be in a non-degenerate state. Bierwagen et al demonstrated elimination of the surface electron accumulation layer (SEAL) by oxygen plasma treatment in MBE-grown c-In 2 O 3 films.…”

“…29) However, the residual carrier concentration was still about 10 18 cm −3 , which is much higher than that of c-In 2 O 3 films. 6,21) To improve the electrical properties, one solution is the growth of thick α-In 2 O 3 film. α-In 2 O 3 film with a thickness of 1.2 μm obtained by increasing the HCl concentration has shown superior electrical properties with a carrier concentration of 8.4 × 10 17 cm −3 and a Hall mobility of 216 cm 2 V −1 s −1 .…”

Thermodynamic analysis of molecular beam epitaxy of group-III sesquioxides

“…However, these substrates are not commercially available and studies of the heteroepitaxial growth of In 2 O 3 on foreign substrates are needed. Numerous groups have attempted to grow c-In 2 O 3 by MBE, [47][48][49] pulsed laser deposition, 50,51) metalorganic CVD, 52,53) HVPE, 9,54,55) and low-pressure CVD. 56) c-In 2 O 3 has also been studied in applications such as Schottky barrier diodes.…”

“…In addition, the high-rate growth of c-In 2 O 3 using a non-hydrogenous HVPE system has been demonstrated based on the results of thermodynamic analyses. 9,55) We recently reported that β-Ga 2 O 3 growth by MBE can be explained by thermodynamics, and we assessed the growth mechanism in detail. 58) However, thermodynamic analyses of α-Al 2 O 3 and c-In 2 O 3 growth by MBE have not yet been reported despite the MBE growth of group-III sesquioxides being a topic of interest to many researchers.…”