Polarization Assisted Interdigital AlGaN/GaN Heterostructure Ultraviolet Photodetectors

An ultraviolet (UV) photodetector (PD) applying the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface with AlGaN symmetrical interdigital structure is designed. The Ti/Al/Ti/Au metal stack is fabricated on the AlGaN interdigital structure for ohmic contacts. The interdigital AlGaN/GaN heterostructure assists to enhance the polarization electric field in the GaN absorption layer. The increased polarization electric field in the GaN absorption layer can facilitate the separation of electrons and holes, and also enhance the transport of the photogenerated carriers. The polarization-enhanced physical mechanism of the AlGaN/GaN 2DEG UV PD is systematically explored by the theoretical simulations. As a result, the designed UV PD exhibits a broadband characteristic with response spectra from 300 to 365 nm and a cutoff wavelength of 365 nm in accordance with the bandgap wavelength of GaN. The normalized photocurrent-to-dark current ratio (NPDR) of $1.31\times 10^{{9}}\,\,\text{W}^{-{1}}$ is measured at 10 V.