A review on the latest progress of visible GaN-based VCSELs with lateral confinement by curved dielectric DBR reflector and boron ion implantation

Abstract

This review introduces the latest progress on gallium nitride (GaN)-based visible vertical-cavity surface-emitting lasers (VCSELs) with features such as plane and curved distributed Bragg reflectors (DBRs) made of dielectric materials and boron ion implantation to form current apertures. This novel class of GaN-based VCSELs allow small apertures down to 3 μm and long cavities of more than 20 μm without the occurrence of diffraction loss. These structures have enabled low threshold currents (e.g., I th = 0.25 mA), high efficiency operation (e.g., WPE = 9.5%), and robust fabrication processes with high lasing yield. All those characteristics are the best among those previously reported GaN-based VCSELs. The proposed structure should facilitate the production of VCSELs formed on semi-polar plane GaN substrates and arrayed VCSELs, which are expected to realize novel light emitters that have been previously difficult to fabricate, such as green VCSELs and watt-class blue VCSEL arrays.

Transfer of 1D Photonic Crystals via Spatially Resolved Hydrophobization

“…Being able to transfer the BSs to a curved surface may allow their integration in light emitting devices in which curved substrates or covers are required. [ 31–33 ]…”

“…Being able to transfer the BSs to a curved surface may allow their integration in light emitting devices in which curved substrates or covers are required. [31][32][33] Apart from demonstrating the transfer of BSs and patterns thereof to various substrates, we can also tailor the hydrophobicity and therefore the sensing response of the 1DPCs after the transfer. In order to allow the transfer in water, the BS had to be hydrophobized to ensure that it does not get damaged upon immersion.…”

49‐2: Invited Paper: Blue and Green VCSEL for Full‐Color Display

“…As the refractive index difference between GaN and AlInN constituting the layer is extremely small (by several percent) in the previously mentioned GaN-based semiconductor DBR, an extremely large number of layers (e.g., 40 pairs) is required to obtain a suitable reflectivity for driving an element. Moreover, the wavelength band at which a higher reflectivity can be produced is approximately 10 nm, which is the main problem [4]. In the former case, the manufacturing time is increased, and in the latter case, the reflectivity is very sensitive to the film thickness and other factors, possibly leading to the deterioration of the yield and other corresponding consequences.…”

“…Since continuous oscillation of the room temperature was first reported in 2008 [2], many studies in this field have been published. Since 2018, multiple organizations have successively announced blue VCSELs driven by a high efficiency of approximately 10% [3,4], indicating that the research phase of this device has ended and practical applications are now the focus in the field. Unlike materials composed of gallium arsenide (GaAs), which have been widely used in VCSELs and are suitable for wavelengths ranging from red to infrared, materials composed of nitride (GaN) can emit light in a wide range of wavelengths (from ultraviolet to green) due to their wide band gap.…”

Visible‐Light Laser Diodes and Superluminescent Diodes: Characteristics and Applications

“…The efforts behind the VCSEL deserve stand-alone studies such as previously reported in [24]. The realization of visible VCSELs required several years of additional development following the demonstration of its edge-emitting counterpart [25,26]. Several challenges involved the overall optical and carrier lateral confinement design, including conductive layers for lateral injection of electrical current, prevention of p-layer absorption, as well as the realization of highreflectivity mirrors with greater than 99% reflectivity, necessary due to the extremely short cavity length.…”