We demonstrate room-temperature pulsed lasing of two types of GaN-based surface emitting lasers (SEL) fabricated without epitaxial regrowth. We present a direct comparison between a circular grating (CGSEL) and a photonic crystal (PCSEL) design. The devices are realized by etching the photonic structures directly into the p-GaN cladding, and utilizing a patterned Indium Tin Oxide (ITO) top contact. Both designs exhibit lasing near 438 nm under pulsed current injection. The CGSEL, incorporating a central defect, achieves a low threshold current density (<1 kA/cm²) and a small divergence angle (≈0.15°) by coupling to a bandgap defect mode. In contrast, the PCSEL shows a higher threshold current density and lases on a 1D band-edge mode, resulting in a cross-shaped far-field pattern. These results confirm the regrowth-free method as a viable route for manufacturable GaN SELs. Crucially, the comparative study identifies the CGSEL defect-mode design as a more robust path toward high-performance lasing in low-confinement epitaxial structures.

In this paper, a novel gate-series-diode structure for the Schottky-type p-GaN HEMTs is proposed, and the impact of the proposed structure on gate-source voltage oscillation is investigated when the device is turned on. The proposed structure is capable of effectively mitigating the gate-source voltage overshoot problem of GaN device, and has little effect on the switching characteristics. The gate voltage oscillations can be greatly stabilized at the steady-state turn-on voltage level when the turn-on voltage is 5 V. Compared with the conventional structure, the overshoots of the proposed structure reduce by 31.4%−71.4% and 40.6%−80.4% respectively under the two pulses, as drain-source voltage rises. The proposed structure is proved to be a potential method on improving gate reliability of the most GaN power devices.