Photoconductive detectors based on partially ordered AlxGa1−xN alloys grown by molecular beam epitaxy

Photoconductive detectors based on partially ordered ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ alloys with AlN mole fractions up to 45% were fabricated and evaluated. The degree of ordering in these alloys was found to increase with the AlN mole fraction and it has a maximum value at about 50%. The resistivity of the ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ films was found to increase from 10 to ${10}^8$ Ω cm by increasing the Al content in the films. Correspondingly, the mobility-lifetime (μτ) product, which was determined by measuring the photoconductive gain, was found to decrease from ${10}^{\text{−2}}$ to ${10}^{\text{−5}}\hspace{0.5em}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/V}.$ These high values of the μτ product at the high AlN mole fraction are attributed to spatial separation and indirect recombination of the photogenerated electron hole pairs, due to band-gap misalignment of the ordered and disordered domains in these films.