Charge-separation photodetectors with long carrier lifetime b.ii.(3)
Abstract
Midwave infrared (MWIR) and longwave infrared (LWIR) photodetectors, both their materials and device structures, have been studied for over a century. However, some fundamental issues are still not fully understood. The state-of-the-art strained-layer short-period superlattices and HgCdTe photodetectors either are quite far from their theoretical limit for performance or have high manufacturing costs due to complicated structure designs and fabrication processes. These issues have prevented these MWIR and LWIR photodetectors from being widely used in many commercial and defense applications, such as night vision for commercial automobiles, environmental monitoring, and chemical sensing. Traditionally, IR photodetectors are designed based on the available materials (such as Si, InGaAs, HgCdTe, PbSe, etc.) with limited flexibility of band structures and other materials properties. For instance, Si has an indirect bandgap which gives long carrier lifetimes but a small absorption coefficient. Therefore, the absorber must be very thick to have sufficient light absorption, which in return results in larger total number of SRH recombination centers because they are volume dependent. On the other hand, the direct bandgap semiconductors, such as InGaAs and HgCdTe, have much larger absorption coefficients. Therefore, they require much thinner absorber layers, which thus have fewer SRH centers. However, the carrier lifetime in direct bandgap semiconductors is very sensitive to SRH and Auger recombination and is ultimately limited by the radiative recombination lifetime, which is much shorter than that in indirect bandgap semiconductors. Clearly, it would be ideal to find a material for photodetectors, which has both a large absorption coefficient and a long carrier lifetime. This proposal focuses on i) careful examination of several conventional photodetector theoretical models, as many of them are based on the equilibrium conditions. The removal of some of these conditions may result in novel material design and device concepts to overcome some fundamental challenges for IR photodetectors; and ii) the design of new materials with ideal properties, such as a large absorption coefficient and long carrier lifetime, and the device layer structure designed to operate under nonequilibrium conditions to further improve the performance of photodetectors in the wavelength range of interest.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 29, 2019
- Source ID
- W911NF1910277
Entities
People
- Yong-hang Zhang
Organizations
- Arizona State University
- Army Contracting Command
- United States Army