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.

Efficiency calculations of heterojunction solar energy converters

Abstract: A theoretical evaluation of the maximum attainable solar conversion efficiencies of p-n and n-p heterodiodes is presented. The calculations are made for some of the theoretically efficient and feasible heterojunctions of IV and III-V group semiconductors. In these calculations, the Anderson diffusion model is used and carrier concentrations of the two semiconductors are so chosen that photo-carriers generated do not have to surmount any junction barrier. The calculated efficiencies are compared with the reported experimental values and with the conventional Si photovoltaic cell.

In situ monitoring of electrical resistance of nanoferrite thin film irradiated by 190 MeV Au14+ ions

Abstract: A highly resistive nanocrystalline thin film of Li0.25Mg0.5Mn0.1Fe2.15O4, deposited by RF magnetron sputtering technique on Si(1 0 0) substrate, is irradiated with 190 MeV Au14+ ions. To probe the swift heavy ion induced modifications in the electrical properties in the film an in situ measurement of electrical resistance using two-probe method is carried out. We observe the value of resistivity comes down drastically from 1.5 × 108 to 1 × 105 Ω cm after irradiation at the fluence of 1 × 1013 ions/cm2. In XRD spectra after irradiation no previous spinel peaks are observed. No loss in oxygen content with fluence is observed. We have presented the observed phenomenon as an effect of formation of amorphized latent tracks on the basis of thermal spike model.

On the recombination of electrons and holes at traps with finite relaxation time

Abstract: Shockley and Read[1] and Hall[2] (SRH) theory for electron hole recombination at traps is modified to include the effect of a finite time of relaxation before the captured electron or hole settles to the ground state. The modified expression for the recombination rate retains all the essential features of SRH theory and includes two additional effects: at low levels of injection lifetime shows a temperature dependence of the type τ = τn0+Cne−ΔEn/kT and at high injection the recombination rate saturates at an upper value Nt/δt where δt is relaxation time and Nt is density of traps.

Solution-processed MoS2 quantum dot/GaAs vertical heterostructure based self-powered photodetectors with superior detectivity

Abstract: The characteristics of a novel 0D/3D heterojunction photodetector fabricated using solution-processed colloidal MoS2 quantum dots (QDs) on GaAs is presented. MoS2 QDs with a dimension of ∼2 nm, synthesized by a standard sono-chemical exfoliation process with 2D layers have been used for the purpose. The microscopic and spectroscopic studies confirmed the formation of semiconducting (2H phase) MoS2 QDs. The photodetectors were fabricated using n-GaAs substrates with two different doping concentrations resulting in n-n heterojunctions between n-type 0D MoS2 QDs and bulk n-GaAs. The devices fabricated using GaAs with a higher doping concentration, showed an increase in the reverse current of the order of ∼102 upon illumination, while the same with a lower doping concentration showed an increase of the order of ∼103. All the heterojunction photodetector devices show a broadband operation over the visible wavelength range of 400-950 nm, with a peak responsivity of the devices being observed at 500 nm. The peak responsivity and detectivity are found to be ∼400 mA W-1 and ∼4 × 1012 Jones, respectively, even without any external applied bias, which are useful for self-powered photodetection. The results indicate that colloidal MoS2/GaAs based hybrid heterostructures provide a platform for fabricating broadband photodetectors by using highly absorbing MoS2 QDs, which may show the pathway towards next-generation optoelectronic devices with superior detection properties.