Modeling and performance characteristics of GaAs quantum well infrared detector structures

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Abstract
Numerous investigations have been reported in recent months confirming the feasibility of infrared detection using optically excited intersubband transitions in GaAs quantum wells in the system GaAs/Al x Ga1−x As. In this paper we present new data on factors such as well width, barrier height, electron exchange interactions, etc. which determine the photoconductive and photovoltaicspectral response of multiquantum well structures, and discuss aspects of parameter control and analysis. Compositional and dimensional control are critically important in determining the type of response (broad or narrow), the wavelength of peak response, optimization at that wavelength, and uniformity across detector arrays. Photoconductive detectors involving transitions between bound states and between bound and free states have both been studied. Also the feasibility of infrared (IR) response in the long‐wavelength infrared (LWIR) spectral range (viz. at 9.5 μm) has for the first time been demonstrated for a photovoltaic‐type multiple quantum well(MQW) structure. In the case of bound‐to‐bound type photoconductive detectors we have observed narrow‐band (Δλ∼1 μm) IR response at the longest wavelengths yet achieved, i.e., out to 12 μm. Measurements on responsivity, dark current, noise, and detectivity indicate that D* values in excess of 1010 cm Hz1/2 W−1 at 77 K (corresponding to responsivities of about 0.24 A/W) are obtainable at λ p of 12 μ and beyond. Our data confirm the role of electron exchange interactions in influencing response wavelength, and indicate that excellent agreement with theory can be achieved if these effects are taken into account.

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