Transition‐Rule Defined Polarization Detection of β‐Ga₂O₃ for Wavelength‐Dependent Sensing of Amino Acid

Abstract Selective electron transitions are critical for polarization detection due to the high sensitivity of optoelectronic conversion to symmetry properties. This work proposes a transition‐rule‐defined wavelength‐dependent polarization detector using low‐symmetry β‐Ga 2 O 3 . Density functional theory calculation is applied to predict the dependence of photoresponse bands on polarization angles. A combination of angle‐resolved polarization Raman spectroscopy and polarized transmittance spectra is utilized to corroborate the anisotropic optical properties of β‐Ga 2 O 3 . Intriguingly, a notable proportional inversion of the polarization ratio ( PR ) emerges at 245 nm when altering the detection wavelength of the β‐Ga 2 O 3 photodetector (PD). Specifically, the photoresponse contrast between E //b and E //c directions, termed responsivity PR , can be boosted from 75 at 254 to 462 at 263 nm, while the minimum reaches 1/388 at 231 nm. The unique phenomenon of wavelength‐dependent polarization detection in β‐Ga 2 O 3 PD well coincides with the density functional theory calculations concerning the selective transition of photoelectrons from split valence bands to the conduction band minimum. Finally, the new transition‐rule‐defined deep‐ultraviolet polarization detector is leveraged to discriminate amino acids. This work demonstrates the remarkable meaning of a delicate control of the selective electron transitions in β‐Ga 2 O 3 polarization PDs for amino acid sensing with high sensitivity and specificity.