We report the measurement of the grain charge on individual dust grains of a dusty plasma Coulomb crystal. These dust grains, grown in a radio frequency plasma from constituent gases, are formed by the aggregation of nanometer sized crystallites. The Coulomb crystal formed from the dust grains appears to be made of mutally repulsive columns of grains confined by the walls of the electrode. A direct measurement of the grain charge was performed using a Faraday cup. The average measured value of the grain charge using this technique was found to be 2 x 105e.This value of the grain charge is approximately consistent with estimates based on the plasma parameters. The corresponding electrostatic interaction energy between the dust grains is found to be 200 times greater than the dust thermal energy.
The natural band alignments of ScxAl1−xN/GaN heterojunctions, with Sc-contents ranging from 0% to 25%, are investigated by first-principles density functional theory with the local density approximation. Type-I ScxAl1−xN/GaN heterojunctions with large conduction band offsets (CBOs) and valence band offsets (VBOs) are found. The band alignment of nearly lattice-matched ScAlN (x = ∼18.75%) with respect to GaN (CBO = 1.74 eV, VBO = 0.34 eV) is also calculated for future implementation in GaN-based quantum wells and power devices. Our findings provide useful band parameters necessary for enabling the implementation of ScAlN alloys in GaN-based power and optoelectronic devices.
The band structure of the dilute-As GaNAs material is explained by the hybridization of localized As-impurity states with the valance band structure of GaN. Our approach employs the use of Density Functional Theory (DFT) calculated band structures, along with experimental results, to determine the localized As-impurity energy level and coupling parameters in the band anti-crossing (BAC) k ∙ p model for N-rich alloys. This model captures the reduction of bandgap with increasing arsenic incorporation and provides a tool for device-level design with the material within the context of the k ∙ p formalism. The analysis extends to calculating the effect of the arsenic impurities on hole (heavy, light and split-off) effective masses and predicting the trend of the bandgap across the entire composition range.
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