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Overcoming solar-blind limitations: 3DEG-induced Fermi-level control in AlGaN phototransistors enables 10 7 out-of-band rejection and 650-photons/s detection

Year: 2025
Type: article
Abstract: Solar-blind ultraviolet (SBUV) photodetectors are critical for applications requiring immunity to solar background noise, such as flame sensing and corona discharge detection. Among these, AlGaN-based heterojunction field-effect phototransistors (HFEPTs) stand out for their high sensitivity enabled by high-conductivity two-dimensional electron gas (2DEG) channels. However, conventional HFEPTs suffer from severe out-of-band photoresponse and persistent photoconductivity (PPC) decay due to deep-level heterojunction defects, limiting their practical utility in sunlight-rich environments. To address this, we propose a 3DEG-engineered AlGaN phototransistor that leverages a composition-graded channel to modulate the Fermi level. This design achieves an unprecedented spectral rejection ratio of 10 7 (260/400 nm)surpassing 2DEG-based devices by five orders of magnitudewhile maintaining sub-fW sensitivity (0.6 fW/cm 2 , equivalent to 650 photons/s). Band structure analysis reveals that the Fermi-level pinning mechanism prevents deep-acceptor-level transitions under both dark and illuminated conditions, effectively suppressing the parasitic out-of-band response and accelerating PPC decay by six orders of magnitude within 10 s. With a specific detectivity ( D *) of 5.110 17 Jones, the 3DEG-PT advances accurate solar-blind operation by detecting weak UV signals under solar irradiation. Our Fermi-level engineering strategy mitigates deep-level impacts, offering a scalable approach for UV photodetectors requiring high background rejection.
DOI: 10.1364/oe.566005
Language: English
Open Access status: gold
Estimated APC paid: $2,270
OpenAlex ID: W4410620480
FWCI: 0.323
Cites: 48
Cited by: 1
Related to: 10