Fabrication And Characterization Of The β-Ga₂O₃ Based Heterojunction

With the development of the microelectronic technology, wide-band-gap semiconductors has aroused increasing interest in researchers due to its excellent abilities and lower energy consumption. Among these materials, β-Ga₂O₃ exhibits one of the most promising direct band gap semiconductors with a band gap of 4.9 e V. It has received a growing concern due to its wide band gap, large dielectric breakdown voltage and excellent ultra violet permeability. Recently, gallium oxide is a natural n-type oxide semiconductor due to its intrinsic oxide vacancies, and it is very difficult to fabricate p-type gallium oxide semiconductor. However, we could grow n-type Ga₂O₃ thin films on other p-type films and then investigate the relevant characteristics and the possible applications of β-Ga₂O₃ through the heterojunction.β-Ga₂O₃ thin films have been fabricated on（0001） sapphire substrate by PLD and magnetron sputtering respectively. By depositing gallium oxide thin films under different temperature, we have studied the influence of the grown temperature on the films. We also investigate the optimal grown condition of cuprous oxide thin films by using Orthogonal Experiment. Finally, we fabricate Ga₂O₃/Cu₂ O heterojunction on ITO substrate and then measure its possible resistive switching characteristics. Possible mechanisms are also present in resistive switching phenomenon in Ga₂O₃/Cu₂ O heterojunction. The detailed works and the main achievements are presented as follows:1. Ga₂O₃ thin films are fabricated on（0001） sapphire substrate by PLD and magnetron sputtering respectively. We investigate the influence of the substrate temperature on the synthesized films. It is observed that the films fabricated by magnetron sputtering shows better crystallinity as the temperature is increased. By detecting all the films made by PLD, we find that the films are mainly composed of amorphous Ga₂O₃ as the temperature is below 600℃, whereas the gallium oxide films fabricated under 750℃ exhibit good quality.2. By using pure copper as the sputtering target material, we have synthesized cuprous oxide thin films through magnetron sputtering. Temperature, gas flow and sputtering power are the influencing factor in the film synthesis. By changing one of these factors and keep other factors constant, we investigate the associations between these factors and the crystalline structure as well as the film quality, and finally we ascertain the requirements to fabricate cuprous oxide thin films. Through the experiment, we find that the crystallization extent and the crystal orientation in cuprous oxide thin films mainly depend on the temperature exchange, while the ass flow have an effect on the valence of the copper ion in the film. Moreover, the sputtering power mainly affect the growth rate of the films.3. Cu₂O/Ga₂O₃ heterostructure is deposited on ITO substrate and then measure the I-V characteristics in the device. With certain measurements, we observed the coexistence of bipolar and unipolar resistive switching in the device. To ensure the stability and reproducibility of the resistive switching in Cu₂O/Ga₂O₃ heterojunction, we scrutinize the endurance property and the retention characteristic as well as the variation of the SET and RESET voltage. We found that these parameter varies in a relative small range. By fitting these I-V curves to professional resistive switching formula, we found that the physical mechanism in these RS behaviors attribute to the combination action of the trapping/detrapping effects and the migration of oxygen vacancies around the interface in Cu₂O/Ga₂O₃ heterojunction.