Laser doping for bandgap engineering

Abstract

Laser doping is used to modify the reflectivity and refractive index of embedded regions in wide bandgap semiconductors for selective detection of gaseous chemical species. Each of the four quadrants of a 1 cm × 1 cm × 300 µm silicon carbide (SiC) sensor are laser doped with a different element; gallium, aluminum, scandium and phosphorus, respectively; to create energy levels that selectively absorb photon emissions from a specific gas molecule chemical composition. For example, the energy level EV + 0.29 created in SiC by the gallium dopant detects only CO2 gas while the energy level EV + 0.23 created in SiC by the aluminum dopant detects only NO. Changes in refractive index, remotely interrogated by a helium neon laser, are correlated to the concentration of the select chemical species. A 1064 nm wavelength Nd:YAG laser source was typically operated at 10-15 W power, 65-200 µm beam diameter and 0.5-0.8 mm/s scan speed using gas, metal-organic or powder dopant precursors. This wireless chemical sensor technology is an advance over interferometers since embedded active regions and a high melting/dissociation point of the sensor, 2730°C for silicon carbide, allow operation in extremely harsh environments.Laser doping is used to modify the reflectivity and refractive index of embedded regions in wide bandgap semiconductors for selective detection of gaseous chemical species. Each of the four quadrants of a 1 cm × 1 cm × 300 µm silicon carbide (SiC) sensor are laser doped with a different element; gallium, aluminum, scandium and phosphorus, respectively; to create energy levels that selectively absorb photon emissions from a specific gas molecule chemical composition. For example, the energy level EV + 0.29 created in SiC by the gallium dopant detects only CO2 gas while the energy level EV + 0.23 created in SiC by the aluminum dopant detects only NO. Changes in refractive index, remotely interrogated by a helium neon laser, are correlated to the concentration of the select chemical species. A 1064 nm wavelength Nd:YAG laser source was typically operated at 10-15 W power, 65-200 µm beam diameter and 0.5-0.8 mm/s scan speed using gas, metal-organic or powder dopant precursors. This wireless chemical sensor te...