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Room-temperature continuous-wave operation of green vertical-cavity surface-emitting lasers with a curved mirror fabricated on {20a??21} semi-polar GaN
摘要： We demonstrate a room-temperature continuous-wave operation of green vertical-cavity surface-emitting laser with a 20-μm-long cavity possessing a dielectric curved mirror formed over a {20?21} semi-polar Gallium Nitride substrate. The emission wavelength and the threshold current were 515 nm and 1.8 mA, respectively. We also confirmed that white light is generated by overlaying three prime colors of light, i.e. red, blue and green, emitted only from vertical-cavity surface-emitting lasers.
关键词： curved mirror,green emission,continuous-wave operation,semi-polar GaN,vertical-cavity surface-emitting laser
更新于2025-09-19 17:13:59
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Simulation Investigation of Laterally Downscaled N-Polar GaN HEMTs
摘要： The N-polar GaN high-electron mobility transistors (HEMTs) have demonstrated a powerful performance as the Ga-polar GaN HEMTs. This investigation aims to show the direct current performance and cutoff frequency (fT) of the planar N-polar GaN HEMTs with gate lengths downscaling from 4 μm to 50 nm by 2-D device simulation. The impacts of traps and gate dielectrics and the roles of the ?eld-dependent mobility and the source and drain series resistances are investigated. For our central-gated device with a 10-nm top GaN channel layer, a 30-nm Al0.3Ga0.7N barrier layer, and a 3-nm Al2O3 gate dielectric, the gate length (LG) as the transition point from the long-channel behavior to the short-channel one is found to be 200 nm. For LG < 200 nm, a linear fT versus LG relation shows up, and notable short-channel effects appear, i.e., the negative shift of the threshold voltage, the increase of the drain-induced barrier lowering, and the almost LG-independent constant maximum transconductance in the saturation region. The degradation of the fT × LG product with the decrease in the aspect ratio between LG and the equivalent gate-channel distance (tt) is shown to be quite small. The LG/tt ratio for 15% degradation of the fT × LG product from its upper limit (19.23 GHz · μm) is 5.5. This small degradation of the frequency characteristics in short-channel devices is attributed to the quite small fringing capacitance of the gate.
关键词： short-channel effect,laterally scaling,N-polar GaN,High-electron mobility transistor (HEMT)
更新于2025-09-12 10:27:22
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Depth-resolved electronic structure measurements by hard X-ray photoemission combined with X-ray total reflection: Direct probing of surface band bending of polar GaN
摘要： We have developed high-throughput depth-resolved electronic structure measurements using hard X-ray photoelectron spectroscopy (HAXPES) combined with X-ray total reflection (TR). By utilizing a steep change of the X-ray attenuation length around the TR condition, we controlled the effective inelastic mean-free-path of photoelectrons from >2 to >12 nm in HAXPES. We applied this method to probe the surface band bending of n-type polar GaN and found the different band bending behaviors in the Ga- and N-polar surfaces. This result is related to the surface contaminations and crystal quality near the surfaces of polar GaN.
关键词： hard X-ray photoelectron spectroscopy,surface band bending,depth-resolved electronic structure,polar GaN,X-ray total reflection
更新于2025-09-04 15:30:14