Conventionally, AlxGa1-xN-based solar-blind photodetector structures are grown at a reactor pressure of 50 millibar. Razeghi's group observed that reducing the growth pressure helps to suppress parasitic pre-reactions and yields more manageable growth rates while still maintaining good material quality. By refining the low-pressure metal-organic chemical-vapor-deposition growth as well as the UV photodetector p-i-n structure, Razeghi's group has successfully fabricated the world's highest quantum efficiency solar-blind UV photodetectors grown on sapphire substrate.
A paper describing the results, "AlxGa1-xN-Based Back-Illuminated Solar-Blind Photodetectors with External Quantum Efficiency of 89%," was published November 5 in the journal Applied Physics Letters.
Although sapphire is the most common choice for back-illuminated devices, researchers also developed alternative low-cost UV photodetectors grown on silicon substrate. Razeghi's group used a novel maskless Lateral Epitaxial Overgrowth (LEO) technique for the growth of a high-quality aluminum nitride (AlN) template layer on silicon substrate. Following the template growth, a p-i-n structure is grown and processed.
This low-cost approach eventually led to the world's first successful implementation of UV-PD structure grown on a silicon substrate. A paper describing the findings, "AlxGa1-xN-Based Solar-Blind Photodetector Based on Lateral Epitaxial Overgrowth of AlN on Si Substrate," was published Oc
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