HgCdTe Multi-colour Infra-red Detectors

Abstract The concept of three-colour detection through a single pixel contact is demonstrated. An intermediate absorber layer is inserted into the centre of the typical back-to-back junction design for two-colour detection. Bias dependent electronic barriers around this intermediate layer control its contribution to the overall signal. One critical parameter for successful operation is low p-doping in these electronic barriers. The sensitivity of device performance to this parameter is demonstrated. Both FPA’s hybridised to read-out chips with switchable inputs, and test diodes for direct assessment, have been produced. This paper concentrates on the test diode assessment, as this provides the greater insight into the operation of the device. It is envisaged that such a device will be used with sequential framing of the different colours to provide quasi-temporal imaging. Keywords: MCT, multi-colour infrared, FPA, MOVPE, mercury cadmium telluride. State of current research HgCdTe (MCT) is often used as the active material for infra-red (IR) detection, due to the wide range over which the band-gap can be tuned. This ternary system also benefits from minimal change in lattice parameter when varying the Cd mole fraction, the x-value in Hg