The year of 2019 marks the 30th anniversary of the invention of the first GaN PN junction light-emitting diode (LED), which was later recognized by the 2014 Nobel Prize in Physics [
Photonics Research, Volume. 7, Issue 12, SUVP1(2019)
Semiconductor UV photonics: feature introduction
The semiconductor UV photonics research has emerged as one of the most heavily invested areas among semiconductor photonics research due to numerous crucial applications such as sterilization, sensing, curing, and communication. The feature issue disseminates nine timely original research and two review papers from leading research groups and companies, covering most frontiers of the semiconductor UV photonics research, from epitaxy, device physics and design, nanostructures, fabrication, packaging, reliability, and application for light-emitting diodes, laser diodes, and photodetectors.
The year of 2019 marks the 30th anniversary of the invention of the first GaN PN junction light-emitting diode (LED), which was later recognized by the 2014 Nobel Prize in Physics [
In comparison, the progress at the shorter-wavelength end of the spectrum has been more moderate for UV devices. The UV devices typically comprise larger-bandgap materials such as Al-rich AlGaN. Larger bandgap increases the activation energy of the typical p- and n-type dopants, thus causing lower layer conductivity. Moreover, the conduction band minimum and the valence band maximum of the larger-bandgap materials further drift away from the workfunction of common metals for contact, leading to a larger Schottky barrier and hence increased contact resistivity. The use of the larger-bandgap materials can also hinder out-of-plane carrier transport due to reduced carrier mobility, compromising injection efficiency. Additionally, the UV emitters can suffer low light extraction efficiency due to absorption of the p-type region and enhanced transverse-magnetic (TM) portion of the emission amid the rising split-off (SO) band. Consequently, most of the UV devices still suffer low performance. Specifically, technically-important commercial UVB and UVC LEDs still operate at a low EQE of a few percent [
The feature issue includes 11 original research and review papers tackling most major aspects of semiconductor UV photonics research including LEDs, LDs, and photodetectors (PDs): epitaxy, characterization, processing, device physics, nanostructures, device reliability, and UV-based communication. They expose cutting-edge research of semiconductor UV photonics and can benefit a broad range of readership.
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Kuhn et al. have demonstrated tunnel junction UVC LEDs by metalorganic vapor phase epitaxy (MOVPE) for the first time to eliminate the absorbing p-type layers [
Due to much smaller mobility than electrons and a potential barrier at the p-type electron blocking layer (EBL), holes have a significantly lower injection efficiency. Zhang et al. have introduced a composition-graded EBL to mitigate the polarization-induced electric field at the EBL to enhance hole injection. The corresponding experiment achieved a high EQE of 7.6% for 275 nm UVC LEDs [
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Xiaohang Li, Russell D. Dupuis, Tim Wernicke. Semiconductor UV photonics: feature introduction[J]. Photonics Research, 2019, 7(12): SUVP1
Special Issue: SEMICONDUCTOR UV PHOTONICS
Received: Nov. 18, 2019
Accepted: --
Published Online: Nov. 28, 2019
The Author Email: Xiaohang Li (xiaohang.li@kaust.edu.sa)