Photoinduced doping in hexagonal boron nitride

Hexagonal boron nitride is shown to exhibit very significant persistent photoconductivity after UV illumination. This behavior can be initiated by sub-bandgap or close to bandgap illumination. Neither temperature nor pressure affects the buildup of photoinduced carriers. The effect persists at least for months at room temperature and is maintained significantly after heating up to 300 & DEG;C. Up to six orders of magnitude increased conductivity has been durably established in the devices, and the effect is reproducible. Double exponential fitting gives time constants up to 4600 days. Irradiation after having saturated the devices is shown to drastically reduce the decay rate. The bulk origin of such effect has been demonstrated. p-hBN/n-AlGaN diodes based on magnesium doped h-BN have been used to determine the type of conductivity through studies of junction capacitance variations under UV irradiation. Depending on illumination wavelength, both n- and p-type durable photoinduced carriers can be produced. These results are of interest for UVC LEDs in which the usual conductive AlGaN layers are still a hurdle toward efficient UV emitters.

Automated summary

Hexagonal boron nitride exhibits persistent photoconductivity after UV illumination, which is not affected by temperature or pressure. The effect can last for months at room temperature and even after heating up to 300°C. Increased conductivity of up to six orders of magnitude has been observed in the devices, with time constants up to 4600 days. Irradiation after saturation reduces the decay rate significantly. Magnesium-doped h-BN diodes have been used to determine the type of conductivity, with both n- and p-type durable photoinduced carriers observed depending on the wavelength of illumination. These findings are important for improving UVC LEDs.