InGaN-based light-emitting diodes (LEDs) were grown and fabricated on nanoscale patterned Si (111) substrates (NPSi). Using anodized aluminum oxide as the etch mask, the NPSi was prepared with an average nanopore diameter of 150 nm and interpore distance of 120 nm. LEDs grown on NPSi exhibit relaxed tensile stress relative to the ones grown on microscale patterned Si (111) substrates (MPSi). Nanoheteroepitaxial lateral overgrowth was significantly promoted on NPSi, which led to extensive dislocation bending and annihilation. The devices made on NPSi exhibit lower leakage current and higher light output power as compared with those on MPSi.

AlGaN/GaN high electron mobility transistors (HEMTs) were grown on Si substrates by MOCVD. In the HEMT structure, a 1 μm GaN buffer layer was partially doped with Mg in an attempt to increase the resistivity and minimize the buffer leakage. The AlGaN/GaN HEMTs grown on undoped and partially Mg-doped GaN buffer layers were processed and the DC characteristics of the devices were characterized for comparing the effect of Mg doping. For the device with the partially Mg-doped GaN buffer layer, a lower drain leakage current density of 55.8 nA/mm, a lower gate leakage current density of 2.73 µA/mm, and a higher off-state breakdown voltage of 104 V were achieved with device dimensions L g /W g /L gs /L gd =1/10/1/1 μm, better than the device with the undoped GaN buffer layer, which has a higher drain leakage current density of 9.2 μA/mm, a higher gate leakage current density of 91.8 µA/mm, and a lower off-state breakdown voltage of 87 V with the same device dimensions. AlGaN/GaN HEMT, Si substrate, MOCVD, breakdown voltage, Mg-doped

AlGaN/GaN high electron mobility transistors (HEMTs) are grown on 2-inch Si (111) substrates by MOCVD. The stacked AlGaN/AlN interlayer with different AlGaN thickness and indium surfactant doped is designed and optimized to relieve the tensile stress during GaN epitaxial growth. The top 1.0 µm GaN buffer layer grown on the optimized AlGaN/AlN interlayer shows a crack-free and shining surface. The XRD results show that GaN(002) FWHM is 480 arcsec and GaN(102) FWHM is 900 arcsec. The AGaN/GaN HEMTs with optimized and nonoptimized AlGaN/AlN interlayer are grown and processed for comparison and the dc and rf characteristics are characterized. For the dc characteristics of the device with optimized AlGaN/AlN interlayer, maximum drain current density 𝐼 dss of 737 mA/mm, peak transconductance 𝐺𝑚 of 185 mS/mm, drain leakage current density 𝐼 𝑑𝑠 of 1.7 µA/mm, gate leakage current density 𝐼𝑔𝑠 of 24.8 µA/mm and off-state breakdown voltage 𝑉BR of 67 V are achieved with 𝐿𝑔/𝑊𝑔/𝐿𝑔𝑠/𝐿 𝑔𝑑 = 1/10/1/1 µm. For the small signal rf characteristics of the device with optimized AlGaN/AlN interlayer, current gain cutoff frequency 𝑓𝑇 of 8.3 GHz and power gain cutoff frequency 𝑓max of 19.9 GHz are achieved with 𝐿𝑔/𝑊𝑔/𝐿𝑔𝑠/𝐿 𝑔𝑑 = 1/100/1/1 µm. Furthermore, the best rf performance with 𝑓𝑇 of 14.5 GHz and 𝑓max of 37.3 GHz is achieved with a reduced gate length of 0.7 µm.