Mechanisms Behind Robust and Reliable High-Temperature Current Transport in AlGaN-Based Solar-Blind UV Photodetector

In this article, we present the fabrication and detailed characterization of an aluminum gallium nitride-based ultraviolet (UV) solar-blind metal–semiconductor–metal photodetector. We have also demonstrated the carrier transport mechanism of the fabricated device under dark conditions, which supports the thermal stability of the device at elevated temperatures. The plasma assisted molecular beam epitaxy grown device exhibits high crystalline quality (screw-type threading dislocation density = ~108 cm−2) and smooth surface morphology (root-mean-square roughness = ~724 pm), enabling us to fabricate the UV solar-blind photodetector. The fabricated device performs well at room temperature (RT), as it demonstrates low dark current on the order of a few tens of pA (6.53 × 10−11 A), high photocurrent (3.91 × 10−6 A), high sensitivity (photocurrent-to-dark current ratio = ~105), high responsivity (~13 A/W), high UV-to-visible rejection ratio (> 103), good detectivity (~1011 Jones), and fast response time (rise time = ~24 μs and fall time = ~23 μs) at 5 V. The analysis of dark currents at elevated temperatures (300–475 K) suggests that carriers undergo thermionic emission in the low-field regime (E < 1.67 kV/cm), thermionic field emission in the mid-field regime (1.67 < E < 10 kV/cm), and Poole–Frenkel emission in the high-field regime (E > 10 kV/cm). These mechanisms govern carrier transport and limit the increase in dark current to only two orders of magnitude relative to RT, thereby confirming the stable behaviour of the device at elevated temperatures. Therefore, the superior RT performance metrics, along with the demonstrated thermal stability under dark conditions at elevated temperatures, motivate further optimization of the device and its potential commercialization for scientific and industrial applications.