Enhancing the Performance of Si/Ga2O3 Heterojunction Solar-Blind Photodetectors for Underwater Applications

Abstract

Epitaxial growth of β-Ga₂O₃ nanowires on silicon substrates was realized by the low-pressure chemical vapor deposition (LPCVD) method. The as-grown Si/Ga₂O₃ heterojunctions were employed in the Underwater DUV detection. It is found that the carrier type as well as the carrier concentration of the silicon substrate significantly affect the performance of the Si/Ga₂O₃ heterojunction. The p-Si/β-Ga₂O₃ (2.68 × 10¹⁵ cm^-3) devices exhibit a responsivity of up to 205.1 mA/W, which is twice the performance of the devices on the n-type substrate (responsivity of 93.69 mA/W). Moreover, the devices' performance is enhanced with the increase in the carrier concentration of the p-type silicon substrates; the corresponding device on the high carrier concentration substrate (6.48 × 10¹⁷ cm^-3) achieves a superior responsivity of 845.3 mA/W. The performance enhancement is mainly attributed to the built-in electric field at the p-Si/n-Ga₂O₃ heterojunction and the reduction in the Schottky barrier under high carrier concentration. These findings would provide a strategy for optimizing carrier transport and interface engineering in solar-blind UV photodetectors, advancing the practical use of high-performance solar-blind photodetectors for underwater application.

Keywords: Ga2O3 nanostructures; photodetector; self-power; solar-blind ultraviolet.

Figure 1

(a) Growth schematic of β-Ga₂O₃ NARs grown on silicon substrates at 900 °C for 30 min. (b) XRD spectrum. (c) (ahv)²-hv plot.

Figure 2

β-Ga₂O₃ nanowires: P1 sample (a) low magnification view and (b) high magnification view. N1 sample (c) low magnification view and (d) high magnification view.

Figure 3

XPS spectra of β-Ga₂O₃ NARs: (a) measured spectra of P1 and N1 samples. (b) Ga 2p spectra. O 1s spectra of (c) P1 sample and (d) N1 sample.

Figure 4

(a) Schematic diagram of the simulated underwater detector evaluation system for β-Ga₂O₃ nanowires. (b) Linear voltage–current (LSV) curves of N1 and P1 samples under 0–1 V bias. (c) I-V response curves under different biases. Rise and decay times of P1 (d) and N1 (e) samples. (f) Photocurrent density under different wavelengths of light. (g) Fitted curves of photoluminescent devices under different light intensities and corresponding photoresponse calculations.

Figure 5

Ga 2p3/2, VBM (a) and Si 2p, VBM (b) and Ga 2p3/2 and Si 2p core level spectrum (c) of P1 sample. Ga 2p3/2, VBM (d) and Si 2p, VBM (e) and Ga 2p3/2 and Si 2p core level spectrum (f) of N1 sample. Energy band schematic of the (g) P1 sample and (h) N1 sample.

Figure 6

(a) I-V curves at 0–1 V for different carrier concentration substrate samples (P1, P2, P3). (b) Comparison of photocurrent densities at 0 V bias, 0.6 mW/cm². (c) Comparison of rise/decay time. (d) Photocurrent densities at different optical wavelengths. (e) Photocurrent densities at different light intensities and (f) the corresponding computed photoresponsivity.