Fabrication of diamond p–i–p–i–p structures and their electrical and electroluminescence properties under high electric fields

Diamond p–i–p–i–p device structures with highly insulating (i) and p-type (p) regions were laterally fabricated using a microscopic etching process of high-pressure/high-temperature-synthesized (HPHT) Ib-type (N-included) diamond with focused ion beams and a homoepitaxial chemical-vapor-deposition (CVD) process. The i regions (at room temperature (RT)) were composed of thinned HPHT diamond with a thickness of 0.5 or 1 μm while the p regions were composed of boron-doped CVD diamond films with a thickness of 0.2 or 0.5 μm. Thus, high electric fields up to ≈ 1 × 107 V/cm were successfully applied to the thinned i regions. When the electrical property of the p–i–p–i–p structures was measured at RT either in a vacuum (5 × 10− 5 Pa) or in 1-atm ambient N2 and Ar gases, dramatic current increases were observed for all the specimens examined at the voltages, V, slightly above the threshold voltages, Vth, depending on the i region thickness. For V > Vth, we observed electroluminescence whose spectra well corresponded to cathodoluminescence spectra taken from the devices. Furthermore, in the measurements in the gases, additional current increases appeared at V substantially higher than Vth due to gas discharges under high electric fields existing outside the diamond devices. These observed phenomena are discussed in relation to an avalanche current amplification process and the band structure of the p–i–p–i–p devices.