Characteristics of III-nitride photodiodes with self-assembled quantum dots

In this work, it has been demonstrated that metal-semiconductor-metal (MSM) photodiodes (PDs) with InGaN self-assembled quantum dots (QDs) were fabricated and compared with conventional InGaN MSM photodiodes. The scanning near-field optical microscope (SNOM) results revealed that such InGaN nanostructures could have better absorption for the near-field light with the wavelength of 457-514 nm. It was found that the InGaN QD photodiode with lower dark current can operate in the normal incidence mode; we could achieve a much larger photocurrent to dark current contrast ratio from MSM photodiodes with nanoscale InGaN quantum dots. It was also found that the measured responsivity of MSM photodiodes with QDs and without QDs approximated to the same in the range of 390-460 nm. Furthermore, the photodiodes with QDs showed higher spectral response than that of the photodiodes without QDs at wavelengths < 350 nm and > 480 nm. (c) 2006 Elsevier B.V. All rights reserved.