Surface Modification of AlGaN Solar-Blind Ultraviolet MSM Photodetectors With Octadecanethiol

We successfully fabricate the AlGaN solar-blind ultraviolet metal-semiconductor-metal (MSM) photodetectors (PDs) with high Al composition of 0.6, and an effective method by modifying organic molecules of Octadecanethiol (ODT) on Al
_0.6
Ga
_0.4
N surface is proposed to enhance the optoelectronic performance of the MSM PDs. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the ODT organic molecules are chemically adsorbed on the surface of the AlGaN active layer successfully. The Al
_0.6
Ga
_0.4
N MSM PD modified with ODT exhibits a cutoff wavelength of ~250 nm, and the dark current is reduced compared to the referential PD without ODT modification, indicating the decreased surface state density due to suppressible oxidation of AlGaN surface by using ODT modification. Moreover, the ODT-modified AlGaN PD shows a high peak responsivity of 2.75 A/W at 10 V, which is enhanced by ~3 times than that of the referential PD without modification.