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.

HRXRD, AFM and optical study of damage created by swift heavy ion irradiation in GaN epitaxial layers

Abstract: Epitaxial GaN layers grown by MOCVD on c -plane sapphire substrates are irradiated with 150 MeV Ag ions at a fluence of 5 × 10 12 ions/cm 2 . Samples used in this study are 2 μm thick GaN layers, with and without a thin AlN cap-layer. Surface morphology is studied using contact mode atomic force microscopy (AFM). Irradiated samples show qualitatively different morphologies as well as quantitative changes. Different kinds of morphology are attributed to specific type of dislocations using the existing models available in the literature. The residual strain and sample quality have been analysed before and after irradiation using high resolution X-ray diffraction (HRXRD). The Lorentzian shape analyses of the experimental scans complement the AFM results. Optical properties are studied by spectrophotometer used in the transmission mode. A sharp band-edge in the as grown samples was observed at ∼3.4 eV. The band-edge absorption broadened due to irradiation and these results have been discussed in view of the damage created by the incident ions which compliment HRXRD results. In general the effect of irradiation induced-damages are analysed as a function of material properties. A possible mechanism responsible for the observations has been discussed.

Periodic electric-field domains in optically excited multiple-quantum-well structures

Abstract: We demonstrate using an ensemble Monte Carlo particle modeling that periodic electric-field domains can arise in optically excited multiple quantum well structures under applied voltage. In particular, the formation of the electric-field distributions with the period equal to twice the structure period is possible. This effect is attributed to the excitation of the recharging waves due to decreasing energy dependence of the capture rate of hot electron capture into quantum wells and nonlocal heating of electrons by electric field.