In this work, flip-chip ultraviolet light-emitting diodes (FCUV-LEDs) on patterned sapphire substrate (PSS) at 375 nm were grown by an atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD). A specialized reactive plasma deposited (RPD) AlN nucleation layer was utilized on the PSS to enhance the quality of the epitaxial layer. By using high-resolution X-ray diffraction, the full-width at half-maximum of the rocking curve shows that the FCUV-LEDs with RPD AlN nucleation layer had better crystalline quality when compared to conventional GaN nucleation samples. From the transmission electron microscopy (TEM) image, it can be observed that the tip and incline portion of the pattern was smooth using the RPD AlN nucleation layer. The threading dislocation densities (TDDs) are reduced from 7 × 10 7 cm −2 to 2.5 × 10 7 cm −2 at the interface between the u-GaN layers for conventional and AlN PSS devices, respectively. As a result, a much higher light output power was achieved. The improvement of light output power at an injection current of 20 mA was enhanced by 30%. Further photoluminescence measurement and numerical simulation confirm such increase of output power can be attributed to the improvement of material quality and light extraction.
A p ϩ -poly-Si gate has been proposed for the fabrication of surface-channel p-metal oxide semiconductor field effect transistors (pMOSFETs) in deep submicrometer complementary MOS (CMOS). 1 Surface-channel devices exhibit a better threshold, subthreshold leakage control, and short channel effect control than those of the conventional buried-channel using the n ϩ -poly-Si gate for p-MOSFETs. However, boron, coming from the BF 2 ϩ -implantation, penetrates easily from poly-Si gate through the gate oxide during the following high temperature thermal cycles at the presence of F. 2 To suppress the boron penetration, methods, such as the stacked poly-Si gate, 3 nitrided oxide, 4 oxide gettering, 5 and nitrogen coimplantation 6 have been reported. However, there is little report on the replacement of implantation source (BF 2 ϩ ) by the solid diffusion source. The Si-B film that deposited in the ultrahigh vacuum chemical vapor deposition (UHV/CVD) system has been reported as the polycrystalline structure with extraordinary high B concentration (2 ϫ 10 22 /cm 3 ). 7 Hence, Si-B can be used as a solid diffusion source to form the p ϩ /n diode due to its high B concentration, and the smaller surface concentration and diffusivity. 8 These shallow junctions formed by the Si-B solid diffusion source exhibited better characteristics than those of conventional BF 2 ϩ -implanted junctions in terms of uniformity, ideality factor, and reverse current. In this paper, a novel Si-B layer, for the first time, is proposed as the solid diffusion source for doping the poly-Si as the p ϩ -poly-Si for p-MOSFETs to alleviate the boron penetration problem. It is found that this new process, which is free of F, depicts a better capability of suppressing the boron penetration than conventional methods employing BF 2 ϩ , or B ϩ implantation.Experimental p ϩ -Poly-Si gate MOS capacitors were fabricated on n-type Si(100) wafer with resistivity of 2-4 ⍀ cm. Field oxide, 550 nm, was grown and active areas were defined. A thin gate oxide 9.5 nm was grown at 900ЊC. A 300 nm poly-Si was then deposited. Samples with the conventional p ϩ -poly-Si gate were conducted by implanting BF 2 ϩ , 50 keV, to a dose of 5 ϫ 10 15 cm Ϫ2 ; or B ϩ , 20 keV, to a dose of 5 ϫ 10 15 cm Ϫ2 . While for the Si-B sample, they were put into a UHV/CVD system to deposit a 35 nm Si-B layer using a 1:1 mixture of the pure SiH 4 and B 2 H 6 (1% in H 2 ) at 550ЊC. The base pressure was 2 ϫ 10 Ϫ8 Torr. Afterward, all samples were annealed in a wet O 2 ambient at the temperature between 850 and 950ЊC for 15-35 min. Si-B layer was oxidized in this annealing process to form SiO 2 and the B diffused into the underlying poly-Si gate forming the p ϩ -poly-Si gate. The formed oxides were then dipped away. Al metal was deposited and patterned for contacts. After aluminum metallization, all samples were annealed at 400°C for 30 min in an N 2 ambient to form a good ohmic contact. The comprehensive effects on the annealing temperature (875-950°C) and time (15-35-min) on the p ϩ -In this pape...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.