Intrinsic AlxGa1-xN photodetectors for the entire compositional range

AlxGa1-xN (0 less than or equal to x less than or equal to 1) ultraviolet photoconductors with cut-off wavelengths from 365 nn to 200 nm have been fabricated and characterized. Various characteristics of the devices, such as photoresponse, voltage-dependent responsivity, frequency-dependent responsivity and noise spectral density, were measured and cross-referenced with optical, electrical and structural characteristics of the material to provide information about the mechanisms taking place during detection. The maximum detectivity reached 5.5x10(8) cm.Hz(1/2)/W at a modulating frequency of 14 Hz. The effective majority carrier lifetime in AlxGa1-xN materials, derived from frequency-dependent photoconductivity measurements, has been estimated to be from 6 to 35 msec. The frequency-dependent noise-spectrum shows that it is dominated by Johnson-noise at high frequencies for low Al-composition samples.