Violet to deep-ultraviolet $InGaN∕GaN$ and $GaN∕AlGaN$ quantum structures for UV electroabsorption modulators

In this paper, we present four GaN based polar quantum structures grown on $c$-plane embedded in $p-i-n$ diode architecture as a part of high-speed electroabsorption modulators for use in optical communication (free-space non-line-of-sight optical links) in the ultraviolet (UV): the first modulator incorporates $∼4–6nm$ thick $GaN∕AlGaN$ quantum structures for operation in the deep-UV spectral region and the other three incorporate $∼2–3nm$ thick $InGaN∕GaN$ quantum structures tuned for operation in violet to near-UV spectral region. Here, we report on the design, epitaxial growth, fabrication, and characterization of these quantum electroabsorption modulators. In reverse bias, these devices exhibit a strong electroabsorption (optical absorption coefficient change in the range of $5500–13000cm−1$ with electric field swings of $40–75V∕μm$⁠) at their specific operating wavelengths. In this work, we show that these quantum electroabsorption structures hold great promise for future applications in ultraviolet optoelectronics technology such as external modulation and data coding in secure non-line-of-sight communication systems.