Effect of Temperature on the Structural and Optical Properties of Ga₂O₃Thin Films Grown on m-plane Sapphire Substrates by Low-Pressure MOCVD

Abstract

In this paper, Ga2O3 films were grown on m-sapphire substances at different temperatures of 600 °C, 700 °C and 800 °C by low pressure MOCVD. By changing the temperature, the crystal phase change of the Ga2O3 thin films grown on the m-sapphire substrates were studied. The effects of temperature on structural characteristics, surface morphology and optical properties of the films were studied systematically. XRD results indicated that the mixture of α-phase and β-phase Ga2O3 films were obtained on the m-sapphire substrates. As the temperature increased to 800 °C, the growth of α-Ga2O3 was weakened. The degree of polycrystallization of β-Ga2O3 decreased, and it gradually changed to preferential growth along the (−402) direction. With increasing of the temperature, the surface morphology of films was obviously changed. AFM measurement showed that the growth temperature has an important effect on the formation of Ga2O3 grains. As the temperature increased, the grain size of the film gradually increased. The analysis results of Raman spectroscopy detected the Raman vibration modes of α-Ga2O3 and β-Ga2O3. In addition, the photoluminescence properties of Ga2O3 thin films have also been systematically studied. Compared with c-sapphire, Ga2O3 thin films grown on m-sapphire substrates have more photoluminescence peaks, and the photoluminescence intensity increased with increasing temperature.

Recent advances in the growth of gallium oxide thin films employing various growth techniques—a review

“…Alongside the anisotropy, bulk β-Ga 2 O 3 suffers from cleavage which is another drawback of β-phase. Moreover, homoepitaxy in (100) orientation is susceptible to high density of twin boundaries which limits the electrical properties like conductivity and mobility.…”

“…Deposition of ( 201) oriented β-Ga 2 O 3 films was achieved on sapphire (0001), MgO (111) and homoepitaxial β-Ga 2 O 3 ( 201) single crystals [111,180,181]. However, β-Ga 2 O 3 (100) growth was performed on various substrates such as GaN (0001)/sapphire, MgAl 6 O 10 (100), gadolinium gallium garnet (Gd 3 Ga 5 O 12 ) (110), KTaO 3 (100) and SrTiO 3 (100) [115,[182][183][184][185]. The ( 201) orientation was also reported on MgO (110) substrate [186].…”

“…Authors found that the refractive index got highly deviated for the case of nonstoichiometric films which is useful information to tailor antireflecting phenomenon in Ga 2 O 3 . The sputtering growth of Ga 2 O 3 thin films have been grown on various substrates like Si (100), GaN, sapphire (0001), MgO (100), MgAl 2 O 4 (100) and SiC (6H) [113,117,209,210]. MgO (100) substrate possesses lowest lattice mismatch with β-Ga 2 O 3 .…”

Comparison of Ga2O3 Films Grown on m- and r-plane Sapphire Substrates by MOCVD

“…It is worth mentioning that the diffraction peak at 64.4°c omes from α-Ga 2 O 3 (30-30) plane, and the remaining diffraction peaks are related to β-Ga 2 O 3 , consistent with our previous research. 38 Interestingly, the diffraction peak intensities related to β-Ga 2 O 3 and α-Ga 2 O 3 plane decreases, on the contrary, the intensity of β-Ga 2 O 3 (−402) diffraction peak at 38.1°increases as the growth pressure increases (as can be seen in Fig. 3b).…”

Influence of Oxygen on β-Ga2O3 Films Deposited on Sapphire Substrates by MOCVD

“…6,15,26 In our previous work, we deposited and investigated a series of Ga 2 O 3 films on different substrates. We analyzed the influence of growth temperature or growth pressure on the crystal phase and orientation of Ga 2 O 3 films deposited on m− or r-plane sapphire substrates, 27,28 and found that the increase in growth pressure can supress the growth rate and grain size of β-Ga 2 O 3 films on sapphire substrate. 29,30 We also investigated the Ga 2 O 3 films deposited on the epi-GaN/sapphire substrates, and it still grew preferentially along the (−201) crystal plane family at higher growth temperatures.…”