Articles you may be interested inOn the origin of the two-dimensional electron gas at AlGaN/GaN heterojunctions and its influence on recessed-gate metal-insulator-semiconductor high electron mobility transistors J. Appl. Phys. 116, 134506 (2014); 10.1063/1.4896900High breakdown voltage in AlN/GaN metal-insulator-semiconductor high-electron-mobility transistors

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We report on the achievement of strong coherent emission from GaAs-based single-walled spiral microtubes, wherein photons are localized in an ultrathin (approximately lambda/25) region embedded with self-organized InGaAs quantum dots. The emission spectra measured at 300 K are characterized by a regular sequence of sharp optical modes with a maximum Q factor of approximately 2500 and separation of approximately 7 meV. The three-dimensional confinement of photons is made possible by the epitaxially smooth tube surface as well as an engineered surface geometry, achieved using a single photolithography step. The experimental results are analyzed using an equivalent planar dielectric waveguide model.

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We report on the fabrication and emission characteristics of InGaAs/GaAs quantum dot microtube ring resonators on Si substrates achieved using a simple but controllable substrate-on-substrate transfer process. We have observed three-dimensionally confined optical modes, including both radial and axial field distributions from quantum dot microtubes on Si with an engineered geometry at 77 K, which agrees well with results calculated using a photonic quasi-Schrödinger equation. An intrinsic Q-factor of ∼2000 is also derived.

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The OFF-state breakdown voltage (BV gd ) characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) on a 4-in. Si substrate were investigated and analyzed. The HEMTs with L gd ¼ 10 m exhibited BV gd of 723 V with the specific on-resistance R DS½ON of 1.3 m cm 2 . Due to the improved ohmic contact, the devices exhibited low R DS½ON values. The power device figure-of-merit (FOM ¼ BV gd 2 =R DS½ON ) is as high as 4:0 Â 10 8 V 2 À1 cm À2 , the highest among the reported values for GaN HEMTs on a 4-in. Si. Due to the low vertical buffer leakage current, a high vertical breakdown voltage of $1200 V has been achieved with the total buffer thickness (d Buff ) of 2.2 m. # 2011 The Japan Society of Applied Physics I II-Nitride semiconductors are emerging as the best candidates for high-speed power switching devices. 1-7) Apart from AlGaN/GaN high-electron-mobility transistors (HEMTs) on SiC and sapphire, AlGaN/GaN HEMTs on Si substrate are emerging as the most suitable choice for commercialization due to their low cost and the availability of larger sizes even up to GaN on 6-in. Si 7) and 8-in. Si 8) substrates. Although the higher lattice-and thermalmismatches of Si generate a large number of dislocations and cracks, AlGaN/GaN HEMTs on Si have shown attractive device performance for high-power applications. 1,[4][5][6][9][10][11][12][13][14] Most high power switching devices require a high three terminal OFF-state breakdown voltage (BV gd ) with low specific on-resistance (R DS½ON ) values. To achieve high BV gd , researchers have tried increasing the buffer layer thicknesses, 1,4,5) using C-doped buffer GaN 11,12) or Fe-doped buffer GaN, 13) wide gate-drain spacing (L gd ), 2,10,11,15,16) incorporation of a field plate, 2,12) AlN passivation, 14) double heterostructure field-effect transistors, 6,16,17) and complete removal of the Si substrate. 18,19) The potential problem in increasing the buffer thickness (d Buff ) is the formation of large wafer bowing which is not good for the fabrication of devices using a conventional lithography process. Due to the double leakage path between the ohmic contact and the Si substrate, Visalli et al. realized that the field plate is limited to enhance the breakdown voltage at the L gd > 8 m. 17) To achieve a higher switching speed with a good power device figure-of-merit (FOM), the device structure should have a higher two-dimensional-electron gas (2DEG) mobility channel with low contact resistance (R c ). For high-power switching device applications, most research groups have used a conducting Si substrate for the fabrication of GaN HEMTs. Recently, we have demonstrated low R DS½ON with high FOM (¼ BV gd 2 =R DS½ON ¼ 2:0 Â 10 8 V 2 À1 cm À2 ) by implementing ohmic recess etching on AlGaN/GaN HEMTs on high-resistivity (HR)-Si (>10;000 cm) with a 1.2-nmthick AlN spacer layer. 15) Umeda et al. realized the boosting of BV gd in GaN HEMTs on an HR-Si substrate with channel stoppers. 20) In this study, we are reporting the improved OFF-state breakdown characteristics of AlGaN/...

Demonstration of submicron-gate AlGaN/GaN high-electron-mobility transistors on silicon with complementary metal-oxide-semiconductor-compatible non-gold metal stack.