High detectivity InGaN-GaN multiquantum well p-n junction photodiodes

InGaN-GaN multiquantum well (MQW) p-n junction photodiodes with semi-transparent Ni-Au electrodes were fabricated and characterized. It was found that the fabricated InGaN-GaN p-n junction photodiodes exhibit a 20-V breakdown voltage and a photocurrent to dark current contrast ratio of ∼10⁵ when a 0.4-V reverse bias was applied. The peak responsivity at 380 nm was 1.28 and 1.76 A/W with a 0.1- and 3-V applied reverse bias, respectively. Furthermore, an internal gain was found from our InGaN-GaN MQW p-n junction photodiodes possibly due to the long-lifetime of GaN based materials. Also, it was found that the low frequency noise of our photodiodes was dominated by the 1/f type noise. For a given bandwidth of 500 Hz, the corresponding noise equivalent power and normalized detectivity D^* were found to be 6.34×10^-13 W and 4.45×10¹¹ cm·Hz^0.5 W^-1, respectively.