Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

Abstract

Abstract:We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV) light-emitting diodes (LEDs), with particular emphasis on the growth approaches for attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences with the introduction of the current status of group III-nitride DUV LEDs and the remaining challenges. This segues into discussion of LED designs enabling high device performance followed by the review of advances in the methods for the growth of bulk single crystal AlN intended as a native substrate together with a discussion of its UV transparency. It should be stated, however, that due to the high-cost of bulk AlN substrates at the time of writing, the growth of DUV LEDs on foreign substrates such as sapphire still dominates the field. On the deposition front, the heteroepitaxial growth approaches incorporate high-temperature metal organic chemical vapor deposition (MOCVD) and pulsed-flow growth, a variant of MOCVD, with the overarching goal of enhancing adatom surface mobility, and thus epitaxial lateral overgrowth which culminates in minimization the effect of lattice-and thermal-mismatches. This is followed by addressing the benefits of pseudomorphic growth of strained high Al-molar fraction AlGaN on AlN. Finally, methods utilized to enhance both p-and n-type conductivity of high Al-molar fraction AlGaN are reviewed.

Physical and technological analysis of the AlGaN-based UVC-LED: an extended discussion focused on cubic phase as an alternative for surface disinfection.

“…Since growth and doping required both accuracy and fine control of fluxes, epitaxy is used as the main deposition technique for LED fabrication. In this way, there are three epitaxial techniques more used such as molecular beam epitaxy (MBE), migration enhanced epitaxy (MEE), and metalorganic chemical vapor deposition (MOCVD) [141][142][143][144]. Besides, the development of combined methods based on MBE, MEE, and MOCVD, such as metal-source flow-rate modulation epitaxy, are of interest as long as Nitrogen flux remains constant reducing the activation energy of accep-tors and smooth surfaces could be produced [145].…”

Morphological diversity of AlN nano- and microstructures: synthesis, growth orientations and theoretical modelling

“…A 2D AlN thin film (AlN TF) is a piezoelectric material with a high acoustic velocity. It is a superior material for applications in high-frequency devices such as surface acoustic wave (SAW) devices, resonators, high-frequency filters, pressure sensors and ultraviolet light emitting diodes (LED) [104][105][106][107]. Therefore, the development of wurtzite (002) or c-axis oriented phase of AlN NFs is vital for most of these applications to obtain higher values of the electromechanical coupling factor, k2t [108].…”

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al x Ga1−x N/GaN Superlattice Layers

“…Ultraviolet light-emitting diodes (UV-LEDs) have generated intensive interest due to their many advantages compared to conventional UV mercury lamps, as well as their wide applicability in numerous applications such as in water purification, medical treatment, analytical sensing and high-density optical storage devices [1][2][3][4]. Among the many developed UV LED technologies, GaN-based UV LEDs have attracted considerable attention owing to their direct bandgap, high electron saturation mobility, and large optical power output density [5,6].…”