a-Axis GaN/AlN/AlGaN Core–Shell Heterojunction Microwires as Normally Off High Electron Mobility Transistors

Abstract

Micro/nanowire-based devices have been envisioned as a promising new route toward improved electronic and optoelectronic applications, which attracts considerable research interests. However, suffering from applicable strategies to synthesize uniform core-shell structures to meet the requirement for the investigations of electrical transport behaviors along the length direction or high electron mobility transistor (HEMT) devices, heterojunction wire-based electronics have been explored limitedly. In the present work, GaN/AlN/AlGaN core-shell heterojunction microwires on patterned Si substrates were synthesized without any catalyst via metalorganic chemical vapor deposition. The as-synthesized microwires had low dislocation, sharp, and uniform heterojunction interfaces. Electrical transport performances were evaluated by fabricating HEMTs on the heterojunction microwire channels. Results demonstrated that a normally off operation was achieved with a threshold voltage of 1.4 V, a high on/off current ratio of 10, a transconductance of 165 mS/mm, and a low subthreshold swing of 81 mV/dec. The normally off operation may attribute to the weak polarization along semipolar facets of the heterojunction, which leads to weak constrain of 2DEG.

Three-dimensional hierarchical semi-polar GaN/InGaN MQW coaxial nanowires on a patterned Si nanowire template

“…27,28 Therefore, the semi-polar growth of GaN/InGaN MQWs is the most preferred and is currently actively studied for GaN-based optical applications in leading laboratories. [29][30][31][32][33][34] In this work, we fabricate the next-generation 3-D semipolar GaN/InGaN hierarchical NWs grown on a Si NWtemplate and characterize their optical properties. The morphology of the Si NWs is controlled with metal-assistedchemical-etching (MACE) together with the morphology of the GaN NWs grown by metal-organic chemical vapor deposition (MOCVD).…”

Epitaxial Lift-Off of Flexible GaN-Based HEMT Arrays with Performances Optimization by the Piezotronic Effect

“…4 d). The maximum transconductance was 27.17 mS mm −1 at V ds = 10 V. The transconductance of GaN HEMT have been compared with the previously reported GaN-based HEMTs [ 7 , 9 , 31 , 32 ], and showed in Table 2 . With the increase in the thickness of AlGaN barrier layer and Al composition, the sheet density of 2DEG is increasing, while the enhancement of electron scattering leads to the decrease in the 2DEG mobility, resulting in a relatively low transconductance.…”

“…With the increase in the thickness of AlGaN barrier layer and Al composition, the sheet density of 2DEG is increasing, while the enhancement of electron scattering leads to the decrease in the 2DEG mobility, resulting in a relatively low transconductance. Further, the unintentionally doped GaN cap layer grown on AlGaN/AlN/GaN can reduce the leakage current and improve gate control performance [ 32 ]. Additionally, the electric measurement of the HEMTs before lift-off was also conducted (Fig.…”

Enhanced Photoresponse of Single GaN Microwire Ultraviolet Photodetectors by Heteroepitaxial AlN Coating Layer

“…Then GaN microwires array were synthesized at 1040 °C, as previously described in detail. [ 39,40 ] A series of AlN shells whose thicknesses were 0 nm, 5 nm, 20 nm, and 35 nm were epitaxially grown by adjusting the TMAl injection time. After that, the wafer was inotropic etched in a mixed solution (5:1:1) of HNO 3 , HF, and deionized water for 10 min to get individual microwire, and this was followed by washing to change the mixed solution to isopropanol.…”