New approaches to direct bandgap III-V materials for LWIR detector applications

Infrared (IR) detector materials based on III-V semiconductors are an affordable alternative to HgCdTe, which is the current material of choice for most high performance IR focal plane array systems fielded in the Army. Based on the assumption that III-V compounds do not have an inherently small bandgap enabling operation out to 10 μm, the long wave infrared (LWIR) range, there has been substantial research investment in superlattice (SL) approaches. For this reason, quantum structures such as quantum well IR photodetectors (QWIPs) and type-II strained-layer superlattices (SLS) are grown to take advantage of confinement effects and to induce an effective bandgap in the desired range. The drawbacks of these approaches include inherently low quantum efficiencies and operating temperature for QWIPs, and very short minority carrier lifetimes for SLS detectors. In this presentation, we will discuss approaches for developing III-V, direct bandgap, dilute N and Bi alloys grown by molecular beam epitaxy (MBE) for LWIR applications.