Fabrication and Characterization of Dual Functional InGaN LED Arrays as the Optical Transmitter and Receiver for Optical Wireless Communications

Abstract

The feasibility of using InGaN/GaN multiple-quantum-well light-emitting diode arrays (LED arrays) as photodiodes (PDs) is investigated experimentally in addition to their light emitting function. Two discrete LED arrays are produced from one 4 × 4 LED array with a parallel-connected pixel configuration. Such compact designs are useful for light emission or detection at the transmitting/receiving terminals of optical wireless communication systems. Despite 4 × 2 LED arrays achieving a light output power of 67.4 mW at 250 mA, they exhibit an optical responsivity (detectivity) of 0.183 A/W (1.61 × 1012 cm Hz 1/2 W −1 ) under ultraviolet light illumination (λ = 380 nm) at zero bias. For 4 × 2 LED arrays, the presence of an appreciable ultraviolet light response, together with a high 3-dB bandwidth (~8 MHz) for modulated light detection, allowed us to build a 15 Mbit/s directed optical link with these LEDs functioning as both the optical transmitter and the receiver. Finally, the unitary LED array-based optical link is capable of real-time transmission of digital audio signals (data rate = 6 Mbit/s) at a propagation distance of 100 cm in free space even though some of the constituent pixels are inactive for light detection.

Underwater Optical Wireless Communications With InGaN LEDs Grown With an Asymmetric Multiple Quantum Well for Light Emission or Detection

“…7, the distinct high (low) level of the detection signals corresponds to the intense (weak) light output of the LDs modulated at 8 MHz. The rise time (τ r ) and fall time (τ d ) can be given by curve fitting of the experimental data using the following equations [39]:…”