II-VI and II-VI/III-V Materials-Based Intersubband Devices

Abstract

The mid-infrared region plays a key role in a diverse set of applications such as defense countermeasures, space communication and selective molecular spectroscopy. The backbone of these applications relies on the high performance emitters and detectors that can be manufactured at lower prices and can operate at room temperature. There are multiple alternatives available in the emitter side yet the detector technology is highly dependent on the mercury-cadmium-telluride (MCT) material system which requires cooling to the liquid nitrogen temperatures, and has a low yield. This dissertation investigates the II-VI material system, namely ZnCdSe/ZnCdMgSe as an alternative to have a broadband coverage in the mid-infrared region and achieve complex tasks like multiband detection where the high device yield is essential.

Multiband detectors are crucial tools to accomplish absolute temperature detection with lower false alarm ratings, yet they have complicated designs and require wide coverage in the mid-infrared range. The wide range tunability of the II-VI material system’s bandgap and the lattice matched growth opportunity on a well-known substrate makes the II-VI the right candidate for the multiband detectors. In this thesis, we demonstrate two-band quantum well infrared photodetectors (QWIPs) centered at the mid-wavelength, 5.0 μm, and the long-wavelength, 8.0 μm. The absolute temperature detection of an unknown object is also demonstrated by using this detector. The two-band QWIPs are also used in the broadband mode where the wide coverage (3.6 μm- 8.7 μm) in the mid-infrared is obtained. Also, the hybrid, II-VI and III-V, quantum cascade detectors are developed to further realize the potential of this new material system. With the hybrid detector technology, the short wavelengths can be spanned by the II-VI material system and the long-wavelengths can be covered by the III-V material system to maximize the performance and spectral coverage by taking advantage of material parameters of both systems. Finally, we also investigate alternative ways to develop high-refractive index contrast cavities in this thesis.

This thesis contributes to the advancement of mid-infrared technology by improving the II-VI material system, and lays out a way to take advantage of the hybrid and complex material systems to achieve high performance devices in the future.