Unveiling Surface‐Vacancy‐Mediated Negative Photoconductivity in γ‐Ga 2 O 3 Quantum Dots for Solar‐Blind Inhibitory Optoelectronic Synapses and In‐Sensor Computing

ABSTRACT Conventional optoelectronic synapses predominantly emulate excitatory neuronal functions via positive photoconductivity, leaving the equally critical inhibitory signaling largely underexplored and vulnerable to visible‐light interference. Here, we unveil a negative photoconductivity (NPC) in the solar‐blind ultraviolet region, achieved at the shortest reported wavelength of 230 nm, in γ ‐Ga 2 O 3 quantum dots (QDs)/graphene heterojunctions. The mechanism originates from surface‐active oxygen vacancies (V O ) that enable reversible O 2 chemisorption; 230 nm illumination triggers hole‐O 2 − recombination, driving interfacial electron transfer that suppresses graphene conductance via a photo‐induced gating effect. This NPC physics delivers an ultrahigh responsivity of −8077 A/W and 279 s retention, emulating inhibitory plasticity (paired‐pulse depression, learning‐forgetting‐relearning). Harnessing the same nonlinear dynamics, we construct an in‐sensor reservoir computing system achieving 96% fingerprint recognition accuracy (91% under 30% noise) without preprocessing, far outperforming conventional visible‐light‐based schemes. Given that the ultrahigh specific surface area of the 0D QDs maximizes the fraction of surface‐exposed, chemically active V O defects for efficient interfacial charge exchange, this strategy establishes a 0D defect‐engineering paradigm for noise‐immune solar‐blind neuromorphic hardware.