Shu-Bai Liu

Bio: Shu-Bai Liu is an academic researcher from National Cheng Kung University. The author has contributed to research in topics: Photodetector & Noise-equivalent power. The author has an hindex of 1, co-authored 3 publications receiving 2 citations.

An Amorphous (Al 0.12 Ga 0.88 ) 2 O 3 Deep Ultraviolet Photodetector

Abstract: The authors report the deposition of an (AlxGa1-x)2O3 amorphous thin film on sapphire substrates by sputter deposition. An amorphous deep ultraviolet (UV) (Al0.12Ga0.88)2O3 photodetector, with a cutoff wavelength at 230 nm, was also fabricated. With −10 V applied bias, it was found the dark leakage current and the linear dynamic range (LDR) of the fabricated photodetector were about 1.23 × 10−9 A and 59.51 dB, respectively. With the same −10 V applied bias, the UVC/UVA contrast ratio was larger than 20. With λillumination = 230 nm and −5 V applied bias, it was found noise equivalent power (NEP) and detectivity (D*) of the fabricated amorphous deep UV (Al0.12Ga0.88)2O3 photodetector were 9.94 × 10−11 W and 2.11 × 1010 cmHz1/2W−1, respectively. These results suggest the fabricated amorphous deep UV (Al0.12Ga0.88)2O3 photodetector herein indicate a cost-effective solution for developing DUV photodetector applications.

Performance Improvement of Co-Sputtering AlGaZnO Solar-Blind Photodetectors

Abstract: The author reported the AlGaZnO photodetector characteristics with various AGO:ZnO co-sputtering power ratio. It was found the optimized on/off ratio and responsivity were about $3.64 \times 10^{5}$ and 0.15 A/W, respectively, at the 10 V applied bias, and with AGO:ZnO power ratio of 80 W:50 W. The UV to visible rejection ratio was $8.08 \times 10^{3}$ , indicated the significant response under UV illumination. The on/off ratio and responsivity could further be improved to $4.2 \times 10^{6}$ and 0.44 A/W, respectively, by annealed at 300°C for an hour, to decrease the defect in the AGZO film. Besides, the photoresponse of the AGZO photodetectors also showed a repeatable and stable switching characteristic. These results indicate the performance of AGZO photodetector were good, and can be a good candidate for low cost, fast fabricated solar-blind application.

Fabrication and Characterization of In0.9Ga0.1O EGFET pH Sensors

Abstract: In this study, the In0.9Ga0.1O sensing membrane were deposited by using the RF magnetron sputtering at room temperature and combined with commercial MOSFETs as the extended gate field effect transistor (EGFET) pH sensors. The sensing performance of the In0.9Ga0.1O EGFET pH sensors were measured and analyzed in the pH value of range between 2 to 12. In the saturation region, the pH current sensitivity calculated from the linear relationship between the IDS and pH value was approximately 56.64 μA/pH corresponding to the linearity of 97.8%. In the linear region, the pH voltage sensitivity exhibited high sensitivity and linearity of 43.7 mV/pH and 96.3%, respectively. The In0.9Ga0.1O EGFET pH sensors were successfully fabricated and exhibited great linearity. The analyzed results indicated that the In0.9Ga0.1O was a robust material as a promising sensing membrane and effectively used for pH sensing detection application.

High Detectivity and Fast Response UV Detector Using Ga Doped SnO₂ Nanowire Arrays

Abstract: Ga doped SnO ₂ Nanowires (Ga: SnO ₂ NWs) based UV photodetector (PD) were fabricated over Si substrate using glancing angle deposition technique. Among various doping concentrations, the 5% Ga: SnO ₂ NWs device exhibited the least dark current (2.67 nA) with high barrier height and highest rectification ratio (~54.6) at −1 V. Samples with Ga doping concentration higher than 5%, induced extra defect level limiting their device performance. Moreover, the 5% Ga: SnO ₂ NWs PD exhibited responsivity and specific detectivity of 16.48 A/W and $6.33\times 10^{13}$ Jones respectively (at 300 nm) and a low noise equivalent power of 53 fW. Furthermore, this device showed fast photoresponse with a rise and fall time of 2 ms and 1.5 ms respectively after doping. Therefore, this letter demonstrates a well-controlled Ga: SnO ₂ NWs based high performance, low-cost UV-PD.

Investigation of AlGaZnO pH Sensors Fabricated by Using Cosputtering System

Abstract: In this study, the extended gate field-effect transistor (EGFET) pH sensors with the aluminum–gallium–zinc-oxide (AGZO) sensing film were fabricated by the radio frequency (RF) cosputtering method at various aluminum–gallium-oxide (AGO):zinc-oxide (ZnO) power ratios. The transfer characteristic curve was measured by the constant voltage mode and the constant current mode at various pH values of 2–12. The pristine AGO sensing film exhibited 23.00 mV/pH and $12.00~\mu \text{A}$ /pH of the pH voltage sensitivity and pH current sensitivity, respectively. The pH sensitivity increased with the increased AGO:ZnO power ratio and achieved the highest value at AGO:ZnO of 80 W:50 W. At this condition, the pH voltage sensitivity and the pH current sensitivity were improved to 30.01 mV/pH and $31.06~\mu \text{A}$ /pH, respectively, and both with the great linearity around 0.99. This was attributed to both the carrier transport improved by the ZnO and the increased surface roughness. From the surface morphology analysis, it was observed that the AGO:ZnO power ratio of 80 W:50 W demonstrated the highest surface roughness of 1.08 nm, related to more surface contact area and more binding sites than other conditions, resulting in the highest pH sensitivity. Therefore, cosputtering AGO and ZnO to form the AGZO sensing film can improve the carrier transport, increase the surface roughness, lead to higher surface reactivity, and enhance the pH voltage sensitivity and the pH current sensitivity.