SiO2 /AlGaN/GaN MOSHFET with 0.7 µm gate-length and fmax / fT of 40/24 GHz

in Electronics Letters (2005), 41(11), 667-668

The performance of SiO2/AlGaN/GaN MOSHFETs is described. The C–V measurements showed slight increase in sheet carrier density after applying 12 nm-thick PECVD SiO2. The devices exhibited gate leakage ... [more ▼]

The performance of SiO2/AlGaN/GaN MOSHFETs is described. The C–V measurements showed slight increase in sheet carrier density after applying 12 nm-thick PECVD SiO2. The devices exhibited gate leakage current of 5 .10 ^-10 A/mm. Small-signal RF characterisation of 0.7 mm gate length devices yielded an fT of 24 GHz and an fmax of 40 GHz, which are comparable to those typical for state-of-the-art AlGaN/GaN HFETs. [less ▲]

Nitrogen implanted GaAs for ultrafast photodetectors and photomixers

in Proc. 5th Intern. Conf. Advanced Semicon. Dev. & Microsystems ASDAM’04 (2004)

Large-area traveling-wave LT-GaAs photomixers for LO application

in SPIE (2004), 5498 (2004)

GaN Nanocolumns on Si(111) Grown b Molecular Beam Epitaxy

in Proc. 5th Intern. Conf. Advanced Semicon. Dev. & Microsystems ASDAM’04 (2004)

GaN nanocolumns are reproducibly grown by plasma-assisted molecular beam epitaxy on Si(111). The nanocolumn density and diameter, 20–150 nm, are controlled by means of the III/V ratio. The nanocolumns ... [more ▼]

GaN nanocolumns are reproducibly grown by plasma-assisted molecular beam epitaxy on Si(111). The nanocolumn density and diameter, 20–150 nm, are controlled by means of the III/V ratio. The nanocolumns grow parallel to the [111] direction of the Si substrate. The columns have been transferred to a Si(100) substrate covered with a layer of 300nm SiO2; single nanowire devices have been fabricated using finger shaped electrical contacts (Ti/Au) obtained by e-beam patterning technique. The electrical transport properties of the resulting metal–semiconductor–metal nanostructures are analyzed by means of current– voltage measurements with and without UV-illumination. [less ▲]

Wet low-temperature gate oxidation for nanoscale vertical field-effect transistors,

in Physica E: Low-Dimensional Systems and Nanostructures (2003), 19(2003), 18-22

In this work, we present an approach towards improving a vertical eld-e ect transistor based on a narrow mesa that is capable of showing complete channel inversion. Contrary to similar concepts it does ... [more ▼]

In this work, we present an approach towards improving a vertical eld-e ect transistor based on a narrow mesa that is capable of showing complete channel inversion. Contrary to similar concepts it does not necessarily require the use of an SOI substrate due to the chosen vertical layer sequence. An important issue during process flow is the limited thermal budget in order to preserve the desired channel length. Here a low-temperature wet oxidation process is investigated to prevent dopant di ffusion in early process steps. Results on the thickness homogeneity and electrical properties of this gate oxide will be presented and discussed. [less ▲]

Investigation of buffer traps in an AlGaN/GaN/Si high electron mobility transistor by backgating current deep level transient spectroscopy

in Applied Physics Letters (2003), 82

The influence of a substrate voltage on the dc characteristics of an AlGaN/GaN high electron mobility transistor ~HEMT! on silicon ~111! substrate is profited to investigate traps that are located between ... [more ▼]

The influence of a substrate voltage on the dc characteristics of an AlGaN/GaN high electron mobility transistor ~HEMT! on silicon ~111! substrate is profited to investigate traps that are located between the substrate and the two-dimensional electron gas channel. The transient of the drain current after applying a negative substrate voltage is evaluated in the temperature range from 30 to 100 °C. With this method, known as backgating current deep level transient spectroscopy, majority carrier traps with activation energy of 200 meV as well as minority carrier traps at 370 meV are identified. The experiments are performed on completed HEMTs, allowing the investigation of the influence of device fabrication technology. [less ▲]

Influence of SiO/sub 2/ and Si/sub 3/N/sub 4/ passivation on AlGaN/GaN/Si HEMT performance,

in Electronics Letters (2003), 39((2003)), 1155-1157

Different influence of SiO2 and Si3N4 passivation on performance of AlGaN=GaN=Si HEMTs is reported. DC characteristics are less enhanced by using SiO2 than Si3N4. This is in agreement with carrier ... [more ▼]

Different influence of SiO2 and Si3N4 passivation on performance of AlGaN=GaN=Si HEMTs is reported. DC characteristics are less enhanced by using SiO2 than Si3N4. This is in agreement with carrier concentration changes after passivation, as follows from Hall data. Small signal RF performance is degraded after applying SiO2 and enhanced after Si3N4 passivation, e.g. for unpassivated devices fTffi17 GHz which decreased to 9 GHz and increased to 28 GHz for SiO2 and Si3N4 respectively. The fmax=fT ratio has not changed after passivation. [less ▲]

Effect of surface passivation on performance of AlGaN/GaN/Si HEMTs

in Solid-State Electronics (2003), 47((2003)), 2097-2103

Performance of intentionally undoped and doped AlGaN/GaN/Si high electron mobility transistors (HEMTs) before and after passivation with SiO2 and Si3N4 is investigated. Hall effect measurements show ... [more ▼]

Performance of intentionally undoped and doped AlGaN/GaN/Si high electron mobility transistors (HEMTs) before and after passivation with SiO2 and Si3N4 is investigated. Hall effect measurements show higher impact of Si3N4 than SiO2 passivation on the carrier concentration increase in the channel. Improvements in DC performance of HEMTs after passivation with SiO2 and Si3N4 correspond to the changes in sheet carrier concentration. Small signal microwave characterisation shows a decrease (from 18.6 to 9 GHz) and an increase (from 18.4 to 28.8 GHz) of the current gain cut off frequency after SiO2 and Si3N4 passivation, respectively. Similar effect of passivation is found in microwave power changes––only about a half of the power is obtained after SiO2 passivation but more than doubled power results from Si3N4 passivation, measured at 2 GHz. Higher density of interface states for SiO2 than Si3N4 passivation is supposed to be responsible for these effects. However, for an optimal design of GaN-based power devices additional studies related to the interface between a passivation layer and GaN are needed. [less ▲]

Investigation of current collapse in doped and undoped AlGaN/GaN HEMTs

in Proc. 4th Intern. Conf. Advanced Semicon. Dev. & Microsystems (2002)

Thin low-temperature gate oxides for vertical field-effect transistor, ,

in Proc. 4th Intern. Conf. Advanced Semicon. Dev. & Microsystems (2002)