A Study on the Growth Window of Polycrystalline Diamond on Si3N4-coated N-Polar GaN

Diamond has the most desirable thermal properties for applications in electronics. In principle, diamond is the best candidate for integration with other materials for thermal management due to its high thermal conductivity. Therefore, if low thermal boundary resistance can be developed between diamond and the semiconductor material, it would most effectively channel the heat away from areas of high power dissipation. Recent advancement of N-polar GaN in high power RF and conventional power electronics motivated us to study the diamond/Si3N4/GaN interface to understand how effectively the heat can be transferred from the GaN channel to diamond heat-sink. Prior studies showed that there are challenges in incorporating diamond with GaN while still maintaining the high crystalline quality necessary to observe the desirable thermal properties of the material. Therefore, in this study we investigated the influence of methane concentration (0.5-6%), gas pressure (40-90 Torr), sample surface temperature (600-850 degrees C), and growth duration (1 similar to 5 h) on polycrystalline diamond growth. The diamond/Si3N4/GaN interface looks abrupt with no signs of etching of the GaN for the samples with methane concentration above 2%, pressures up to 90 Torr, and temperatures < 850 degrees C, allowing for incorporation of diamond close to the active region of the device. This approach contrasts with most prior research, which require surface roughening and thick growth on the backside.