Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Design and Fabrication of Multi-finger Field Plate for Enhancement of AlGaN/GaN HEMT Breakdown Voltage

Abstract: The design and fabrication of gate/source connected multi-finger field plate structures using TCAD ATLAS simulation software is presented. The designed field plate structures are fabricated on indigenous AlGaN/GaN HEMT devices. AlGaN/GaN HEMT devices with field plate structures exhibit about three times improvement in breakdown voltage of device and are in close agreement with the simulation results. Integration of field plates in device have resulted in higher VDS (drain to source voltage) operation and improvement in output power of AlGaN/GaN HEMT devices. Incorporation of field plates also decrease the reverse leakage current of HEMT devices.

Passivation effects on reactive-ion-etch-formed n-on-p junctions in HgCdTe

Abstract: The formation of n-on-p junctions by reactive ion etching (RIE) of HgCdTe using an H2/CH4 plasma has previously been demonstrated to produce high-performance photodiodes. To fully exploit the inherent advantages of this process, a compatible surface-passivation technology that provides long-term stability is required. This paper examines the effects of thermally evaporated CdTe- and ZnS-passivation on RIE-formed photodiodes undergoing low-temperature baking in a vacuum at temperatures typically used for Dewar bake-out. Experimental results show that as a single passivation layer, neither CdTe nor ZnS are suitable for vacuum packaging of RIE-formed diodes that are to be operated at cryogenic temperatures. A double passivation layer, however, consisting of CdTe passivation and an insulating overlayer of ZnS, produces photodiodes that are stable throughout 175 h, approximately 1 week, of 80°C baking in a vacuum.

Kondo effect and spin-orbit coupling in graphene quantum dots.

Abstract: The Kondo effect is a cornerstone in the study of strongly correlated fermions. The coherent exchange coupling of conduction electrons to local magnetic moments gives rise to a Kondo cloud that screens the impurity spin. Here we report on the interplay between spin–orbit interaction and the Kondo effect, that can lead to a underscreened Kondo effects in quantum dots in bilayer graphene. More generally, we introduce a different experimental platform for studying Kondo physics. In contrast to carbon nanotubes, where nanotube chirality determines spin–orbit coupling breaking the SU(4) symmetry of the electronic states relevant for the Kondo effect, we study a planar carbon material where a small spin–orbit coupling of nominally flat graphene is enhanced by zero-point out-of-plane phonons. The resulting two-electron triplet ground state in bilayer graphene dots provides a route to exploring the Kondo effect with a small spin–orbit interaction. The Kondo effect has been observed in a variety of systems, including carbon nanotube quantum dots and graphene in the presence of impurities. Here, the authors report the observation of the Kondo effect in bilayer graphene quantum dots and study its interplay with weak spin-orbit coupling.

Valence of YbS under pressure: A resonant inelastic x-ray emission study

Abstract: We present spectroscopic data on the electronic structure of YbS under pressure. From resonant x-ray emission and x-ray absorption spectra in the high-resolution partial fluorescence yield mode, we find that the Yb valence increases from 2.3 at ambient pressure to 2.6 at 360 kbar. The accuracy of these estimates is enhanced by a combined analysis of emission spectra measured as a function of the incident and emitted energy. The spectral line shapes reflect the mixed character of the electronic states, intermediate between atomic and bandlike.

Irradiation effect on dielectric properties of NiMn0.05Tix(Zn, Mg)xFe1.95−2xO4 ferrite thin films

Abstract: Swift heavy ion induced modifications on dielectric properties of NiMn 0.05 Ti x (Zn 2+ , Mg 2+ ) x Fe 1.95−2 x O 4 for x =0.0, 0.2 thin films were studied. Thin films of NiMn 0.05 Ti x (Zn 2+ , Mg 2+ ) x Fe 1.95−2 x O 4 for x =0.0, 0.2 were grown on Si substrate using RF magnetron sputtering. The films were irradiated with 190 MeV Ag ion for three different fluence values 5 × 10 10 , 5 × 10 11 and 1 × 10 12 ions/cm 2 . The dielectric constant, e , and dielectric loss, tan δ , as a function of frequency from 1 kHz to 1 MHz were measured at room temperature for unirradiated and irradiated thin films. The e for NiMn 0.05 Fe 1.95 O 4 and NiMn 0.05 Ti 0.2 Mg 0.2 Fe 1.55 O 4 of unirradiated and irradiated film decreases with frequency, which is explained by Koops’ model. The dielectric constant at high frequency decreases with increase in ion irradiation fluence values. The irradiated NiMn 0.05 Ti 0.2 Zn 0.2 Fe 1.55 O 4 films show an anomalous behavior. The dielectric constant below 20 kHz increases with irradiation as compared to pristine film, whereas above 20 kHz the dielectric constant for irradiated samples were less than the pristine samples but it increases with irradiation. Further the dielectric loss show an increase with the irradiation. All the irradiated films show a resonance peak, which was not present in the pristine films. Also with the increase in the dose the resonance peak was found to be shifted to the lower frequency.