Abstract
GaN-based light emitting diodes (LEDs) have been shown to effectively operate down to nanoscale dimensions, which allows further downscaling the chip-based LED display technology from micro- to nanoscale. This brings up the question of what resolution limit of the illumination pattern can be obtained. We show two different approaches to achieve individually switchable nano-LED arrays. We evaluated both designs in terms of near-field spot size and optical crosstalk between neighboring pixels by using finite difference time domain (FDTD) simulations. The numerical results were compared with the performance data from a fabricated nano-LED array. The outcome underlines the influence of geometry of the LED array and materials used in contact lines on the final illumination spot size and shape.
Highlights
GaN exhibits relatively slow surface recombination velocities, which gives the ability to downscale GaN-based light emitting diode (LED) technology to the nanoscale
In order to validate the simulation results and experimentally determine the effective spatial dimension of the light spot produced by the LEDs, shadow images of a metallic test pattern defined by electron-beam lithography (EBL) were acquired and analyzed by extracting the edge spread function (ESF)
A single LED has been activated with a constant bias current of 800 nA, and a shadow image with 80 × 476 pixels was acquired by moving the glass carrier with the metal pattern along x and y with steps of 200 nm using micropositioners, covering an area of 16 × 95.2 μm2
Summary
GaN exhibits relatively slow surface recombination velocities, which gives the ability to downscale GaN-based light emitting diode (LED) technology to the nanoscale. Emission of light was observed for nanowire devices down to diameters of ∼100 nm [1,2,3,4] This property of GaN opens the possibility to create chip-integrated, dense nano-LED arrays having spatial resolution that is significantly higher than today’s devices. Nano-LED technology opens a new area of chip-based devices potentially operating in a super-resolution regime applicable in highly-resolved microscopy [13,14] or structured illumination systems for, e.g., mask-less lithography [1] or optogenetics [15]. We briefly describe the design and numerical setup for devices under investigation We discuss their optical characteristics obtained by numerical simulations and compare the results with characteristics of a fabricated device.
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