Al x Ga 1−x N (0⩽x⩽1) ultraviolet photodetectors grown on sapphire by metal-organic chemical-vapor deposition

Abstract

${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ (0⩽x⩽1) ultraviolet photoconductors with cutoff wavelengths from 365 to 200 nm have been fabricated and characterized. The maximum detectivity reached 5.5×10⁸ cmHz^1/2/W at a modulating frequency of 14 Hz. The effective majority carrier lifetime in ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ materials, derived from frequency-dependent photoconductivity measurements, has been estimated to be from 6 to 35 ms. The frequency-dependent noise spectrum shows that it is dominated by Johnson noise at high frequencies for low-Al-composition samples.