Vanita Devi

Band offset studies in pulse laser deposited Zn1−xCdxO/ZnO hetero-junctions

The valence and conduction band offsets of Zn1−xCdxO/ZnO hetero-junctions deposited by pulsed laser deposition technique were estimated by X-ray photoelectron, valence band, and UV-visible spectroscopy. Type-II band alignment (staggered gap) with ratios of conduction band to valence band offsets (ΔEC/ΔEV) was found to be 0.77 and 0.59 for Zn0.95Cd0.05O/ZnO and Zn0.90Cd0.10O/ZnO hetero-structures, respectively, which can be used in longer wavelength regime optoelectronic devices. The higher value of valence band offset as compared to conduction band offset suggests that the transport at interface is mainly due to electrons.

Structural and optical properties of Cd and Mg doped zinc oxide thin films deposited by pulsed laser deposition

The 7 wt % Cd doped and 15 wt % Mg doped ZnO thin films were deposited on quartz substrate by pulse laser deposition system. The structural and optical properties of the prepared ZnO, Cd:ZnO and Mg:ZnO films were investigated by X-Ray diffraction (XRD), photoluminescence and UV-Vis spectroscopy techniques. XRD results indicate that the doped ZnO films maintain wurtzite crystal symmetry without any defects and are oriented along c- axis. Photoluminescence studies show a sharp band edge emission peak at 384 nm for pure ZnO film. This peak is blue shifted to 381 nm with Cd doping and red shifted to 395 nm with Mg doping. UV visible absorption studies reveals a decrease in band gap with Cd doping and an increase in band gap with Mg doping.

Band offset measurements in Zn1−x Sb x O/ZnO hetero-junctions

Accurate knowledge of the alignment of conduction and valence bands of layers at the heterojunction and warrant knowledge of the band offsets at the interface is essential for Zn1−x Sb x O/ZnO based quantum well device designing and modeling. Under this scenario, valence band offsets of Zn1−x Sb x O/ZnO heterostructures grown by the pulsed laser deposition technique was measured by photoelectron spectroscopy and consequently, the conduction band offset was calculated by UV-visible spectroscopy. The change in band alignment has been observed with the dopant (Sb) concentration. Ratios of conduction band offset to valence band offset were estimated to be 1.67 and 0.04 for x = 0.03 and 0.06, respectively, for Sb doped films. A Type-II band alignment was observed at the Zn0.97Sb0.03O/ZnO interface, whereas the Type-I band alignment took place at the Zn0.94Sb0.06O/ZnO interface.

Structural and optical properties of Zn1-xCdxO thin films

Thin films of Zn1-xCdxO (x=0, 0.05, 0.1) were deposited on glass substrate by pulsed laser deposition technique. The structural and optical properties of the prepared thin film samples were investigated using X-Ray Diffraction (XRD), Atomic force Microscopy, UV-visible and Photoluminescence spectroscopy. XRD results confirm that deposited films were oriented along c-axis and contain wurtzite crystalline symmetry. XRD and AFM result reveled that, the grain size decreases with increasing Cd concentration. UV-visible spectroscopy results reveal high transmittance for all the thin film samples. A reduction in the optical band gap energy with increasing Cd composition was observed through the Tauc plot method.

Droop Improvement in InGaN/GaN Light-Emitting Diodes by Polarization Doping of Quantum Wells and Electron Blocking Layer

-Polarization doping in quantum wells and electron blocking layer is proposed to improve the emission intensity and efficiency droop of InGaN light-emitting diodes (LEDs). Band diagrams and the internal quantum efficiencies of LEDs are theoretically studied by the ATLAS simulation program. Numerical results show that the internal quantum efficiency of polarization doped LED structures are improved by 25% as compared to un-doped structures which can be due to accumulation of high density two-dimensional electron gas in quantum wells.

Structural and electrical properties of P doped ZnO films

Structural, electronic and electrical properties of Phosphorus doped ZnO thin films deposited using pulsed laser deposition technique, on P-type Si (111) substrate are studied. X-ray diffraction measurements shows that undoped ZnO and Phosphorus doped ZnO films oriented along c-axis and maintains wurtzite crystalline symmetry. The change in grain size occurs by Phosphorus doping, which can be correlated to stress comes due to presence of Phosphorus. The changes in electronic structure has been observed by Phosphorus doping in ZnO thin films, which is understood from X-ray absorption spectroscopy. Hall measurements shows n-type behavior of Phosphorus doped ZnO samples.Structural, electronic and electrical properties of Phosphorus doped ZnO thin films deposited using pulsed laser deposition technique, on P-type Si (111) substrate are studied. X-ray diffraction measurements shows that undoped ZnO and Phosphorus doped ZnO films oriented along c-axis and maintains wurtzite crystalline symmetry. The change in grain size occurs by Phosphorus doping, which can be correlated to stress comes due to presence of Phosphorus. The changes in electronic structure has been observed by Phosphorus doping in ZnO thin films, which is understood from X-ray absorption spectroscopy. Hall measurements shows n-type behavior of Phosphorus doped ZnO samples.

Electronic and multiferroic properties of Zn0.85Mg0.15O thin film

Thin film sample of Zn0.85Mg0.15O was prepared on Si (100) substrate by pulsed laser deposition and its structural, electronic, magnetic and ferroelectric properties were investigated. The Zn0.85Mg0.15O thin film sample is found to show room temperature multiferroic properties; suitable for device fabrication.