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

Photoconductive detectors based on partially ordered AlxGa1-xN alloys with AlN mole fractions up to 45% were fabricated and evaluated. The degree of o rdering in these alloys was found to increase with the AlN mole fraction an d it has a maximum value at about 50%. The resistivity of the AlxGa1-xN fil ms was found to increase from 10 to 10(8) Ohm cm by increasing the Al conte nt in the films. Correspondingly, the mobility-lifetime (mu tau) product, w hich was determined by measuring the photoconductive gain, was found to dec rease from 10(-2) to 10(-5) cm(2)/V. These high values of the mu tau produc t at the high AlN mole fraction are attributed to spatial separation and in direct recombination of the photogenerated electron hole pairs, due to band -gap misalignment of the ordered and disordered domains in these films. (C) 1999 American Institute of Physics. [S0003-6951(99)02815-6].