arXiv subjects

M. Bockowski

Publications and source records attributed to M. Bockowski.

3 recordsLinked to original sources

arXiv2026

Comparison of reverse current mechanisms in GaN Schottky diodes grown on sapphire versus ammonothermal GaN substrates

In this work, we analyse the reverse current mechanisms in GaN Schottky barrier diodes (SBDs) grown on sapphire and native GaN substrates. For the sapphire-substrate sample, two conduction mechanisms are identified: Poole-Frenkel emission (PFE) and trap-assisted tunneling (TAT), with corresponding trap energy levels of 0.9 eV and 0.3 eV, respectively. In contrast, only PFE is observed in the GaN-substrate sample, with a trap energy of 0.75 eV, suggesting that the presence of TAT is related to the higher dislocation density in structures grown on sapphire substrates. The leakage mechanisms and associated trap energies are extracted by comparing experimental current-voltage (I-V) characteristics with a model that includes thermionic emission and tunneling contributions for different temperatures, from 298K up to 443K.

physics.app-ph↗

arXiv2022

Defects Evolution and Mg Segregation in Mg-implanted GaN with Ultra-High-Pressure Annealing

Annealing Mg-implanted homoepitaxial GaN at temperatures at or above 1400 {\deg}C eliminates the formation of inversion domains and leads to improved dopant activation efficiency. Extended defects in the form of inversion domains contain electrically inactive Mg after post-implantation annealing at temperatures as high as 1300 {\deg}C (one GPa N2 overpressure), which results in a low dopant activation efficiency. Triple axis X-ray data show that the implant-induced strain is fully relieved after annealing at 1300 {\deg}C for 10 min, indicating that the strain-inducing point defects formed during implantation have reconfigured. However, annealing at temperatures of 1400 {\deg}C to 1500 {\deg}C (also one GPa N2 overpressure) eliminates the presence of the inversion domains. Annealing at these higher temperatures and for a longer time does not have any further impact on the strain state. While residual defects, such as dislocation loops, still exist after annealing at and above 1400 {\deg}C, chemical analysis at the dislocation loops shows no sign of Mg segregation. Meanwhile, an overall decreasing trend in the dislocation loop size and density is observed after annealing at higher temperatures and longer times. Earlier work [1] addressing electrical measurements of these types of samples showed that annealing at 1400 {\deg}C leads to a dopant activation efficiency that is an order of magnitude higher than that observed at 1300 {\deg}C. This work complements the earlier work by identifying the microscopic defects (inversion domains) which incorporate Mg, and points to the benefits, in terms of defect density and p-type dopant activation, of using higher temperatures annealing cycles to activate Mg in GaN.

cond-mat.mtrl-sci↗

arXiv2005

Heat capacity of $α$-GaN: Isotope Effects

Until recently, the heat capacity of GaN had only been measured for polycrystalline powder samples. Semiempirical as well as \textit{first-principles} calculations have appeared within the past few years. We present in this article measurements of the heat capacity of hexagonal single crystals of GaN in the 20-1400K temperature range. We find that our data deviate significantly from the literature values for polycrystalline materials. The dependence of the heat capacity on the isotopic mass has also been investigated recently for monatomic crystals such as diamond, silicon, and germanium. Multi-atomic crystals are expected to exhibit a different dependence of these heat capacities on the masses of each of the isotopes present. These effects have not been investigated in the past. We also present \textit{first-principles} calculations of the dependence of the heat capacities of GaN, as a canonical binary material, on each of the Ga and N masses. We show that they are indeed different, as expected from the fact that the Ga mass affects mainly the acoustic, that of N the optic phonons. It is hoped that these calculations will encourage experimental measurements of the dependence of the heat capacity on isotopic masses in binary and more complex semiconductors.

cond-mat.mtrl-sci↗