Combination of GaAs-based heterojunctions with semiconductor oxides for applications in optoelectronic devices: 1) GaAs/SnO2, 2) GaAs/ZnO: bulk acoustic wave resonators

Author(s)

Diego Henrique de Oliveira Machado

• Document type: Doctoral Thesis
• Press: Bauru. 2020-06-16.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências. Bauru
• Defense date: 2020-04-30
• Advisor: Luis Vicente de Andrade Scalvi

Abstract

This work aims to present the development and the main conclusions obtained so far regarding the combination of GaAs-based heterojunctions with semiconductor oxides, for applications in optoelectronic devices. The text has been divided in two main parts, where the first one is related to the synthesis and production of SnO2, associated with the formation of the heterostructure GaAs/SnO2; and the second one if focused on the production of bulk acoustic wave resonators, with frequencies in GHz range, based on GaAs/ZnO. In the first part, attention was given to SnO2 films, deposited by two techniques: sol-gel dipcoating and resistive evaporation, on soda-lime glass substrates, and on GaAs, quartz and a-SiO2 substrates. SnO2 was also deposited on GaAs film deposited by sputtering. In the case of resistive evaporation, the sol-gel route is also used to prepare the powder which is used as a precursor for resistive evaporation of SnO2 films, then, by combining these two techniques. Optical and electrical properties of Er3+ -doped SnO2 thin films were investigated as well as the hybrid structure GaAs/SnO2 .Among the main results were: 1) different luminescence spectra of Er3+ ion when depositing SnO2 on glass or GaAs substrate; 2) scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) for SnO2 films deposited by resistive evaporation show a relationship of the thermal annealing temperature with the concentration of Er ions in the surface layers; 3) this concentration of Er3+ ions on the surface of evaporated SnO2 films affects the photoluminescence spectra and the gas adsorption on the surface; 4) SEM and optical microscopy for resistive evaporation deposited SnO2 films show that these films have good adhesion on GaAs layers, being related to the combination of sol-gel and resistive evaporation techniques. In the second part of the work, where a combination of MBE deposited GaAs with ZnO oxide was used, the generation and propagation of high frequency bulk acoustic waves (BAW) in GaAs substrates was investigated, using ZnO and AlN piezoelectric thin films produced by RF-sputtering. It was verified the electroacoustic conversion efficiency of BAW resonators based on these piezoelectric materials. The propagation of longitudinal acoustic waves in the range 1 to 20 GHz (10 to 300 K) was investigated by means of radiofrequency reflection measurements, allowing the determination of the intrinsic acoustic absorption coefficient in GaAs (α) at frequencies of the order of GHz. (AU)

• FAPESP's process: 16/12216-6 - Heterojunctions of SnO2 for applications in optoelectronic devices:1) GaAs/SnO2, 2) grafeno/SnO2
• Grantee: Diego Henrique de Oliveira Machado
• Support Opportunities: Scholarships in Brazil - Doctorate