Reduced influences of the HPHT substrates on the electronic quality of homoepitaxial CVD diamond layers and on their ultraviolet detector performance

We have carried out a detailed estimation of the influences of the high-pressure/high-temperature-synthesized (HPHT) Ib substrate on the crystalline quality of the homoepitaxial diamond and on the performance of the ultraviolet (UV) detector. The H3 center related luminescence peaks were observed even from the homoepitaxial diamond film having a thickness of 250 μm on a HPHT Ib substrate, suggesting that carriers excited in the epitaxial diamond layer can diffuse over a rather long distance to the HPHT substrate when the quality of the epitaxial layer is sufficiently high. Furthermore, we have attempted to efficiently reduce the long-distance carrier diffusion phenomenon by inserting a boron-doped layer between the epitaxial layer for the detection and the HPHT Ib substrate. The electrically-floating B-doped layer inserted between the homoepitaxial layer and the HPHT substrate efficiently reduced the long-distance carrier diffusion phenomenon, and substantially improved the performance of the UV detector fabricated on a low-quality HPHT Ib substrate.

Research Highlights
► The irregular growth mode observed at the substrate edges had great influence on the crystalline quality of the epitaxial diamond layer.
► Carriers excited in the epitaxial diamond layer can diffuse over a rather long distance to the HPHT substrate.
► Electrically-floating B-doped layer between the epitaxial diamond layer and the HPHT substrate can efficiently reduce the long-distance carrier diffusion phenomenon.