Group-III Nitride Substrate Carbon Gradient for Defect Control

The patent applies local quality by creating a non-uniform carbon concentration distribution within the crystal structure. The carbon concentration is set to be higher in specific regions (such as near interfaces or in buffer layers) and lower in other regions, allowing local resistance reduction without causing uniform lattice constant changes throughout the entire crystal. This spatially differentiated impurity distribution enables electrical conductivity improvement in specific areas while maintaining overall lattice constant control and preventing widespread dislocation defects and cracking.

The patent applies parameter changes by precisely controlling the carbon concentration parameter within specific numerical ranges and gradients. Rather than simply increasing carbon concentration uniformly, the invention optimizes the carbon concentration parameter to fall within a window that provides sufficient electrical conductivity improvement while remaining below the threshold that would cause excessive lattice constant changes. The carbon concentration is controlled to be within specific ranges (e.g., 1×10^17 to 1×10^20 atoms/cm³ in certain regions) to achieve the desired balance between conductivity enhancement and defect prevention.

The patent applies dynamics by implementing time-dependent control of gas supply concentrations during the crystal growth process. The carbon element-containing gas concentration is dynamically adjusted based on the growth stage: higher concentrations are supplied during early to middle growth stages to maintain adequate growth rate, while the concentration is reduced or optimized during later stages to prevent excessive carbon incorporation that would alter the lattice constant. This dynamic, stage-specific gas supply strategy enables the system to adaptively balance growth rate and lattice constant control throughout the growth process.