Three-color MOVPE MCT diodes

ABSTRACT The drive towards improved target recognition has led to an increasing interest in detection in more than one infrared band. Many groups have demonstrated two-color detection, typically by employing two back-to-back junctions, one for each color. In this paper we describe a method for introducing a third color via an absorber of intermediate wavelength placed between the two junctions. Electronic barriers are used to isolate this intermediate region. The design and location of the barriers in the structure are such that the barrier height is readily controlled by the applied bias, enabling the intermediate color to be turned on by applied bias. To provide the positional and doping control needed in the materials structure, MOVPE growth of MCT is used. Both FPA’s hybridised to a 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 sequen tial framing of the different colors to provide quasi-temporal imaging. The successful demonstration of the 3-color concept is described. Keywords: MCT , multi-color infrared, FPA, MOVPE, mercury cadmium telluride.