Exploration on performance of two-dimensional GaN photocathodes with uniform-doping and variable-doping structure

In this paper, the properties of two-dimensional (2D) gallium nitride (GaN) photocathodes with a uniform doping and variable doping structure are studied by using Mg as a doping element based on first principles. The stability, bandstructure, work function, density of state and optical properties of the GaN bilayer and GaN trilayer in two-doped ways are investigated. The results show that formation energy of variable doping structure is less than that of the uniform doping structure, which means that the variable doping structure is more stable. At the same time, the formation energy increases with increase of layers. The pristine GaN bilayer has an indirect bandgap, while the doped GaN bilayer transforms into a direct bandgap. The impurity levels appear in a forbidden band of doped GaN trilayers, which is favorable for electron transition. The results of work function reveal that variable doping structure has lower vacuum barriers and more electron escape numbers, which proves that it can improve the quantum efficiency of photocathodes. Finally, the analysis of optical properties shows that the uniform doping structure has better optical properties than that of the variable doping structure.

Thermal neutron transmutation doping of GaN semiconductors

High quality Ge doping of GaN is demonstrated using primarily thermal neutrons for the first time. In this study, GaN was doped with Ge to concentrations from 1016 Ge atoms/cm3 to 1018 Ge atoms/cm3. The doping concentrations were measured using gamma-ray spectroscopy and confirmed using SIMS analysis. The data from SIMS analysis also show consistent Ge doping concentration throughout the depth of the GaN wafers. After irradiation, the GaN was annealed in a nitrogen environment at 950 °C for 30 min. The neutron doping process turns out to produce spatially uniform doping throughout the whole volume of the GaN substrate.

Advancing layered cathode material's cycling stability from uniform doping to non-uniform doping

Dopant segregation induced precipitates can further improve the cycling stability of a P2-layered cathode due to the precipitation strengthening effect, which conceptually validates that non-uniform doping has big advantage over uniform doping.

Bulk Junctionless Transistor (JLT) with Non-Uniform Doping: A high Performance and Scalable device

In this paper we have presented the non-uniformly doped bulk Junctionless transistor (JLT) and investigated bulk-JLT and SOI-JLT with non-uniform doping in terms of its electrical performance parameters and short channel effects (SCEs) parameters comparatively. Effective thickness of channel depends on non-uniform doping distribution parameters and this affects the performance of bulk-JLT notably, however it is not so in case of SOI-JLT. The effect of non-uniform doping on electrical characteristics of JLTs (bulk and SOI) in terms of Subthreshold Slope (SS), ON-current, OFF-Current and ON/OFF current ratio has been investigated, and the non-uniformly doped bulk-JLT exhibits high ON/OFF ratio (109 for 20 nm Gate Length). Moreover, the non-uniformly doped bulk-JLT also shows improved short-channel effects (SCEs) parameters (such as Drain Induced Barrier Lowering, Threshold Voltage variations etc.) compared to SOI-JLT. Lastly, the effect of standard deviation, dielectric constant, substrate doping, and well biasing on the device performance are examined to further improve the performance of bulk-JLT independently.