[en] Highlights: • Phase separation and thermal annealing effects on the (GaIn)_2O_3 films were studied. • Phase separation were observed when substrate temperature is higher than 300 °C. • Thermal annealing the film resulted in (GaIn)_2O_3 film without phase separation. - Abstract: In this study, we investigated the phase separation phenomenon and post thermal annealing effects on the (GaIn)_2O_3 films deposited on sapphire substrates by pulsed laser deposition. Films grown at substrate temperature higher than 300 °C showed phase separation while films grown at substrate temperature lower than 200 °C revealed homogenous elements distributions with amorphous structure. Thermal annealing had no obvious effects on (GaIn)_2O_3 films grown at substrate temperature higher than 300 °C. The clusters remained on the surface of the films after thermal annealing treatment. On the other hand, however, by thermal annealing the film deposited at room temperature, (GaIn)_2O_3 film with smooth surface, homogenous element distribution, high orientation crystal and high optical transmittance observed by means of scanning electron microscope, energy dispersive spectrometer, X-ray diffraction and spectrophotometer was successfully obtained, paving a way for obtaining high quality (GaIn)_2O_3 film without phase separation

[en] Highlights: • Single phase MgZnO films were successfully obtained in all Mg content range at lower substrate temperatures. • The Mg content in the MgZnO films can be controlled by changing the Mg content in the targets and substrate temperature. • The bandgap of MgZnO films can be tailored by adjusting the Mg content in the film. - Abstract: MgZnO films are grown on (0 0 0 1) sapphire substrates by pulsed laser deposition. The crystal structure and optical properties of the MgZnO films have been systematically investigated with the methods of energy dispersive spectroscopy (EDS), X-ray diffraction and spectrophotometer. The EDS results show that the MgZnO films with different Mg contents can be prepared by adjusting the Mg content in the target and substrate temperature. Single phase MgZnO films are successfully obtained in all Mg content. The structural transition from hexagonal to cubic phase has been observed at the Mg content around 0.4. Optical analysis indicates that the bandgap of the MgZnO films can be tailored by controlling the Mg content in the films

[en] ZnTe homoepitaxial layers have been grown by synchrotron-radiation-excited growth using diethylzinc and diethyltelluride with nitrogen carrier gas. Effects of carrier gas on the growth rate and photoluminescence (PL) properties of the ZnTe layers have been investigated. No remarkable difference was found in the growth rate of the deposited layer between hydrogen and nitrogen carrier gases at low substrate temperature up to 60 deg. C. However, at high substrate temperature, the growth rate obtained using nitrogen carrier gas exhibits only a slight reduction, while that using hydrogen is significantly reduced. PL spectra exhibit a sharp excitonic emission at 2.375 eV associated with shallow acceptor in the ZnTe layer grown under the condition of various VI/II ratios and substrate temperature condition by using nitrogen carrier gas, different from the case of hydrogen carrier gas

[en] Thulium doped gallium oxides (Tm-Ga₂O₃) films were deposited on Si substrates by the pulsed laser deposition method. Blue emissions (476 nm and 460 nm) can be observed by the naked eye from Tm-Ga₂O₃/Si light emitting diodes (LEDs). The threshold voltage of Tm-Ga₂O₃/Si LEDs is 6.3 V, which is lower than that of Tm-GaN/Si devices. By combining our previously reported green emission from Er-Ga₂O₃ and red emission from Eu-Ga₂O₃, strong blue emission from Tm-Ga₂O₃ can realize the full-color LEDs with the single host of Ga₂O₃. These results open a pathway for integrating Ga₂O₃ based full-color LEDs with mainstream Si technology. (author)

[en] ZnTe homoepitaxial films have been deposited at substrate temperatures between 27 deg. C and 100 deg. C by synchrotron-radiation-excited growth using diethylzinc and diethyltelluride. Effects of diethylzinc transport rate and substrate temperature upon the photoluminescence properties of the ZnTe films have been clarified. Strong deep level emissions centered at 1.85 and 2.1 eV related to defects such as vacancy-impurity complex become emerged with increasing diethylzinc transport rate or substrate temperature. A sharply excitonic emission at 2.375 eV associated with shallow acceptors is observed and neither a donor-acceptor pair recombination nor a deep level luminescence signal is detected in the spectrum of the film grown under the nearly stoichiometric condition, which indicates that ZnTe films of good quality can be grown even at room temperature by this growth technique

[en] Europium doped Ga₂O₃ films were deposited on sapphire substrates by using pulsed laser deposition. The influences of substrate temperature on structural and optical properties have been systematically investigated by means of X-ray diffraction and photoluminescence. High quality single (−201) oriented Ga₂O₃ film can be obtained at substrate temperature of 400 °C. The emission intensity of Eu³⁺ decreased solely with elevated temperature by using 325 nm light, while it had a maximum value at a certain temperature under 488 nm light. Both of the experimental data were well fitted by the luminescence dynamic equation models, suggesting that the variation of the emission intensity may be attributed to the thermal activated distribution of electrons among ⁷F_j and thermal quenching effect.

[en] In₂O₃ films were deposited on c-plane sapphire substrates by using pulsed laser deposition (PLD) without and with oxygen plasma at various growth temperature. The crystal structure, optical properties and surface morphologies were determined by X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and atomic force microscope. XRD analysis revealed that all films have the body-centered cubic structure with a preferable (222) orientation. The results of XRC, Raman spectroscopy and spectrophotometer prove the superiority of plasma-assisted PLD. The low temperature growth of crystal In₂O₃ film paves the way to be compatible with the established silicon microfabrication processes. (author)

[en] ZnTe growth has been investigated, using (100) oriented ZnTe substrates, by the synchrotron-radiation-excited epitaxy at a very low pressure of ∼ 10^-5 Torr. Diethylzinc (DEZn) and diethyltelluride (DETe) were used as source materials. The transport rate ratio of DETe to DEZn is an important factor for improving the crystallinity of the film. The epitaxial growth is attainable even at room temperature. The growth rate characteristics of epitaxial film as functions of substrate temperature and DETe transport rate suggest that the adsorption of source materials followed by the decomposition due to the surface excitation is important in the ZnTe growth. (author)

[en] The ZnO/ZnTe heterojunction was fabricated by using a room temperature direct bonding (RTDB) technology. Satisfactory rectification properties were confirmed, and the forward voltage drop V_F was observed to be 2.3 V. The results indicate that RTDB technology is effective for fabricating ZnO/ZnTe heterojunction. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Terbium (Tb)-doped Ga${}_2$O${}_3$ films are grown on Si substrates by pulsed laser deposition at a substrate temperature of 500 °C. The electroluminescence (EL) peaks detected at 488, 543, 587, and 622 nm from the Tb-doped Ga${}_2$O${}_3$/Si light-emitting diodes (LEDs) correspond to the ${}^5$D${}_4$-${}^7$F${}_6$, ${}^5$D${}_4$-${}^7$F${}_5$, ${}^5$D${}_4$-${}^7$F${}_4$, and ${}^5$D${}_4$-${}^7$F${}_3$ transitions, respectively. The EL intensity initially increases with current up to 70 mA, followed by a decrease at higher currents. Notably, there is no discernible shift in the EL spectra peaks as the operating current varies from 5 to 90 mA. These findings imply that the Tb-doped Ga${}_2$O${}_3$/Si LED, characterized by its remarkable wavelength stability, holds significant potential for advancing the development of highly efficient LEDs across diverse applications. (© 2024 Wiley‐VCH GmbH)