High performance mid-wavelength quantum dot infrared photodetectrors for focal plane arrays

Abstract

Quantum dot infrared photodetectors (QDIPs) have recently emerged as promising candidates for detection in the middle wavelength infrared (MWIR) and long wavelength infrared (LWIR) ranges. This is due to the QDIPs' absorption of normally incident light, potential room-temperature operation and high responsivity. These unique features are a direct consequence of the three-dimensional confinement potential achieved in quantum dots that provides a discrete density of states and a longer life time of excited electrons due to the "phonon bottleneck" effect. Here, we report our recent results for mid-wavelength QDIPs grown by low-pressure metalorganic chemical vapor deposition. The device structure was gown on a semi-insulating GaAs (001) substrate. The active region consisted of ten In_0.68Ga_0.32As quantum dot layers separated by 35nm-thick In_0.49Ga0.₅₁P barriers. Three monolayer of In_0.68Ga_0.32As self-assembled via the Stranski-Krastanov growth mode and formed lens-shaped InGaAs quantum dots with a density around 3×10¹⁰cm^-2. The peak responsivity at 77 K was measured to be 3.4 A/W at a bias of -1.9 V with 4.7 μm peak detection wavelength. A high peak detectivity of 3×10¹² cmHz^1/2/W was achieved at 77 K and a bias of -1.9 V. The temperature dependent device performance was also investigated. The improved temperature insensitivity compared to quantum well infrared photodetectors (QWIPs) was attributed to the quantum dots properties. The device showed a background limited performance temperature of 220 K with a 45° field of view and 300K background. Focal plane arrays (FPAs) based on these devices have been developed. The preliminary result of FPA imaging is presented.