Dual-band Ultraviolet Photodetector with Voltage-tunable Spectrum Ability

Abstract

In this dissertation the voltage-tunable dual-band UV PD has been investigated The dual-band UV PD consisted of MgZnO ZnO Ga2O3 GaN and SiO2 which was grown by RF magnetron sputter MOCVD PECVD respectively For the ZnO UV PD the best thin-film quality was at 300C annealing and to had the highest PDCR to 1810 18 at 5V And due to better crystal quality the device annealing at 300 ℃ exhibited the best responsivity at 5V which was 7 27 × 10-3 and was located at 380 nm For the Ga2O3 UV PD the annealing condition at 800 ℃ had the best performance of ultraviolet to visible light rejection ratio and the maximum of responsivity was located at 250nm For the MgZnO UV PD no matter used 10% Mg content target or 20% Mg content target the cristal quality and real Mg composition were increased as arisen annealed temperature And the best condition was annealing at 700 ℃ Moreover the wavelength absorbed edge was 337 nm and 310 nm which device made by 10% and 20% Mg content target respectively For the MgZnO dual-band UV PD the structure should be inserted as a blocking layer to prevent the Mg atom diffusion on the one hand On the other hand it separated the mainly absorbed wavelength between low and high bias voltage; otherwise the edge between layers with different Mg composition would be blurred The edge of the absorbed wavelength was shifted about 10 nm which from 310 nm to 320 nm Based on this the SiO2 inserting layer was considered in our voltage-tunable UV PD design which was design to cross different ranges of absorbed wavelength For voltage-tunable UVB to UVA dual-band UV PD the MgZnO/SiO2/ZnO dual-band UV PD had an obvious voltage-tunable dual-band performance with 200 nm MgZnO thickness And the edge of the absorbed wavelength shifted about 55 nm from 310 nm (UVB) to 365nm (UVA) For voltage-tunable UVC to UVB dual-band UV PD the Ga2O3/MgZnO dual-band UV PD had an obvious voltage-tunable dual-band performance without Ga2O3 annealing And the edge of the absorbed wavelength shifted about 70 nm which from 250 nm (UVC) to 320nm (UVB) Furthermore inserted 25 nm SiO2 between Ga2O3 and MgZnO could extend the MgZnO absorbed wavelength to appear at 24 V For voltage-tunable UVC to UVA dual-band UV PD the Ga2O3/SiO2/GaN dual-band UV PD accidentally exhibited a band-pass liked performance at 600 ℃ annealings which with 100nm SiO2 thickness When the thickness of SiO2 increased to 400 nm all of the photon-electrons of devices were generated from Ga2O3 The Ga2O3/SiO2/GaN dual-band UV PD had an obvious voltage-tunable dual-band performance with 200 nm SiO2 thickness and 300 ℃ Ga2O3 annealings And the edge of the absorbed wavelength shifted about 115 nm which from 250 nm (UVC) to 365nm (UVA)

Date of Award	2021
Original language	English
Supervisor	Shoou-Jinn Chang (Supervisor)