Visible light communication (VLC) has attracted widespread attention for wireless communications. The popularity of GaN‐based light‐emitting diodes (LEDs) has also laid a solid foundation for the application of VLC. As the light source of VLC, LED's modulation bandwidth directly determines the speed of communication. Herein, reviewing progress on modulation bandwidth improvement schemes of GaN LEDs transmitter is reviewed, covering aspects from epitaxial to devices. Epitaxial approaches include c‐polar facet epitaxial optimization, non/semipolar facet epitaxial growth, and chip scheme such as micro‐LEDs, nano‐LEDs, resonant cavity‐LEDs (RC‐LEDs), plasmon, and metacavity LEDs. In terms of white LEDs, approaches to tackle the slow Stokes transfer and long carrier life for conventional phosphors including new color‐conversion materials (CCMs) and new energy transfer routes are reviewed. This review promotes the development of GaN‐based LEDs as the transmitter for high‐speed VLC.

The development of an efficient group-IV light source that is compatible with the CMOS process remains a significant goal in Si-based photonics. Recently, the GeSn alloy has been identified as a promising candidate for realizing Si-based light sources. However, previous research suffered from a small wafer size, limiting the throughput and yield. To overcome this challenge, we report the successful growth of GeSn/Ge multiple-quantum-well (MQW) p-i-n LEDs on a 12-inch (300-mm) Si substrate. To the best of our knowledge, this represents the first report of semiconductor LEDs grown on such a large substrate. The MQW LED epitaxial layer is deposited on a 12-inch (300-mm) (001)-oriented intrinsic Si substrate using commercial reduced pressure chemical vapor deposition. To mitigate the detrimental effects of threading dislocation densities on luminescence, the GeSn/Ge is grown pseudomorphically. Owing to the high crystal quality and more directness in the bandgap, enhanced electroluminescence (EL) integrated intensity of 27.58 times is demonstrated compared to the Ge LED. The MQW LEDs exhibit EL emission near 2 μm over a wide operating temperature range of 300 to 450 K, indicating high-temperature stability. This work shows that GeSn/Ge MQW emitters are potential group-IV light sources for large-scale manufacturing.

Surface anti-reflection (AR) with nanometer-scaled texture has shown excellent light trapping performance involving optical devices. In this work, we developed a simple and lithography-free structure replication process to obtain large scale surface cup-shaped nano-pillar (CSNP) arrays for the first time. A method of depositing was used for pattern transfer based on PMMA pre-coated through-hole anodic aluminum oxide (AAO) thin film (~500 nm), and eventually, the uniformity of the transferred nanostructures was guaranteed. From the spectrum (250 nm~2000 nm) dependent measurements, the CSNP nanostructured Si showed excellent AR performance when compared with that of the single-polished Si. Moreover, the CSNP was found to be polarization insensitive and less dependent on incidence angles (≤80°) over the whole spectrum. To further prove the excellent antireflective properties of the CSNP structure, thin film solar cell models were built and studied. The maximum value of J_ph for CSNP solar cells shows obvious improvement comparing with that of the cylinder, cone and parabola structured ones. Specifically, in comparison with the optimized Si₃N₄ thin film solar cell, an increment of 54.64% has been achieved for the CSNP thin film solar cell.

The emergence of vertical GaN devices solves the problem of insufficient voltage withstand capacity of horizontal GaN devices. However, the current output capability of vertical GaN devices is not comparable to that of lateral GaN devices. So we propose a Al_0.3Ga_0.7N/GaN current-aperture vertical electron transistor with a SiO₂–In_0.05Ga_0.95N hybrid current-blocking layer (CBL). Through simulation and in-depth study of the proposed device, the results show that the GaN/InGaN secondary channel enhances the saturation output current of the device, achieving a saturated output current (I _DSS) of 985 mA mm⁻¹ and a transconductance (G _m) of 256 mS mm⁻¹, which are 30% and 25% higher than that of the single-channel SiO₂ CBL device, respectively. The breakdown voltage is 230 V and the on-resistance (R _on) is only 0.58 mΩ cm².

Due to the lack of efficient light sources compatible with complementary metal oxide semiconductor technology, the development of silicon-based photonic integrated circuits has been restricted. Germanium (Ge), with its small bandgap difference between the direct and indirect valleys, becomes a promising candidate for light emission when tensile strain is applied to modify its band structure. However, achieving high and uniform strain in electrically active devices remains a challenge. In this work, we present a biaxially tensile strained Ge light-emitting diode with a vertical p-i-n junction, fabricated on a germanium-on-insulator substrate. The energy difference between the Γ valley and the L valley is further reduced by introducing a biaxial tensile strain of ∼0.77% through the microbridge structure. A 1.7-fold enhancement is observed in the direct bandgap photoluminescence intensity at room temperature. Furthermore, the peak intensity of direct bandgap electroluminescence increases threefold at 400 K compared to room temperature. These results demonstrate the potential of biaxially strained Ge for efficient, Si-compatible light sources, advancing the integration of group-IV materials in silicon photonics.