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See detailImpact of thermal annealing on nonequilibrium carrier dynamics in single-crystal, freestanding GaAs mesostructures
Mikulics, Martin; Hardtdegen, Hilde; Adam, Roman et al

in Semiconductor Science & Technology (2014), 29

We report on the impact of thermal annealing to carrier transport and transient, subpicosecond photoresponse of freestanding GaAs mesostructures. Our measurements included micro-photoluminescence and dark ... [more ▼]

We report on the impact of thermal annealing to carrier transport and transient, subpicosecond photoresponse of freestanding GaAs mesostructures. Our measurements included micro-photoluminescence and dark current and responsivity studies as well as optical femtosecond characterization. The fabricated GaAs mesostructures consisted of both mesowires and platelets that were integrated into coplanar striplines to form a photoconductive switch. We demonstrate that an optimized annealing process of our mesostructures, performed at 600 ◦C for 20 min, led to restoring bulklike properties of our freestanding devices. They exhibited dark currents below 600 pA at 10 V bias, responsivity of 0.2 A W−1 at 30 V, and mobility as high as 7300 cm2 V s−1. The annealed freestanding GaAs photodetectors were characterized by subpicosecond carrier relaxation dynamics with negligible trapping and a cutoff frequency of 1.3 THz. The latter characteristics make them excellent candidates for THz-bandwidth optoelectronics. [less ▲]

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See detailNon-uniform distribution of induced strain in gate-recessed AlGaN/GaN structure evaluated by micro-PL measurements
Mikulics, Martin; Hardtdegen, Hilde; Gregušová, Dagmar et al

in Semiconductor Science & Technology (2012), 27(10), 105008-105008

Micro-photoluminescence (μ-PL) studies were performed on AlGaN/GaN heterostructure field effect transistors (HFETs) with different gate-recessing depths. It was found that μ-PL is the method of choice for ... [more ▼]

Micro-photoluminescence (μ-PL) studies were performed on AlGaN/GaN heterostructure field effect transistors (HFETs) with different gate-recessing depths. It was found that μ-PL is the method of choice for detecting dry etching damage and simultaneously recording strain and stress in the HFET GaN layer. Lateral sub-μm resolved mapping shows that the strain in the GaN layer after recessing is partially relaxed and non-uniform. [less ▲]

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See detailFemtosecond and highly sensitive GaAs metal–semiconductor–metal photodetectors grown on aluminum mirrors/pseudo-substrates,
Mikulics, Martin; Adam, Roman; Sofer, Zdenek et al

in Semiconductor Science & Technology (2010), 25(7), 75001

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See detailImpact of surface treatment under the gate on the current collapse of unpassivated AlGaN/GaN heterostructure field-effect transistors
Kordoš, P.; Bernát, J.; Gregušová, D. et al

in Semiconductor Science & Technology (2006), 21 (2006)

Unpassivated GaN/AlGaN/GaN/SiC heterostructure field-effect transistors were fabricated on intentionally undoped and 5 × 1018 cm−3 modulationdoped material structures. The influence of surface treatment ... [more ▼]

Unpassivated GaN/AlGaN/GaN/SiC heterostructure field-effect transistors were fabricated on intentionally undoped and 5 × 1018 cm−3 modulationdoped material structures. The influence of surface treatment before gate metallization on the gate leakage and drain current collapse of the devices was observed. In the case of a short HCl treatment (∼5 s), a relatively small gate leakage (<10−6A mm−1 at −6 V gate bias) but large current collapse (∼30% after applying 5 μs wide pulses) were measured. On the other hand, devices with a longer surface treatment (15–20 s) showed an increased gate leakage (>10−4A mm−1) and a simultaneously negligible current collapse (<5%). This effect is qualitatively similar in devices prepared on the undoped and doped heterostructures. It is assumed that a thin interfacial oxide layer under the gate might be responsible for a lower leakage current and a larger current collapse of the devices. [less ▲]

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See detailAnnealing of Schottky contacts deposited on dry etched AlGaN/GaN,
Kuzmík, J.; Javorka, P.; Marso, Michel UL et al

in Semiconductor Science & Technology (2002), 17((2002).), 76-78

The influence of annealing on properties of Pt Schottky contacts deposited on the electron cyclotron resonance plasma etched surface of an AlGaN/GaN heterostructure has been investigated. It is found that ... [more ▼]

The influence of annealing on properties of Pt Schottky contacts deposited on the electron cyclotron resonance plasma etched surface of an AlGaN/GaN heterostructure has been investigated. It is found that rapid thermal annealing (450 ◦C and 40 s in nitrogen gas), performed after metal deposition, allows for the preparation of Schottky contacts with similar or better properties than those obtained on a non-etched surface. This procedure is suitable for the realization of recessed high-quality Schottky contacts of AlGaN/GaN HEMTs. [less ▲]

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