SBIR-STTR Award

The proposal overall objective is to develop a rigorous understanding of the electronic structure and semiconductor-laser application related physics properties of the novel III-V-Bi material system. The sophisticated, graphical user interface driven software tools already established for standard III-V semiconductor heterostructures will be extended and generalized to become applicable for the bismide system. Detailed theory-experiment comparisons will be performed to establish a reliable materials data base. Using this as input for the systematic, fully microscopic calculations of the gain and intrinsic losses will allow for rigorous physics-based modeling of III-V-Bi based optoelectronic devices. This approach will make it possible to design, guide and provide feedback on growth, fabrication and evaluation of semiconductor quantum-confined structures with type-I or type-II band alignment that provide optical gain in the 3-5 ìm (0.41 to 0.25 eV) window. The key technical objective of Phase I is a proof of concept study to establish the potential of III-V-Bi based material systems as lasers operating in 3-5 µm window at watt-level powers. This will be pursued via a comprehensive literature search and evaluation of atomistic level bandstructure calculation methods, validation of these and of NLCSTRs microscopic modeling tools against experimental data provided by subcontractor Arizona State University

Benefits:
The strong demand for high quality semiconductor laser systems for dual-use technologies that must satisfy stringent military specifications as well as future state-of-the-art commercial applications, creates a critical need for a commercial software package that can leverage a cost effective, fast track to the final laser product. Future improvements in semiconductor wafer growth quality will require the implementation of improved wafer processing diagnostics during in-situ growth within MBE and MOCVD systems. For example, state-of-the-art MBE growth systems contain multiple chambers designed to carry out wafer diagnostics during material growth. Future markets for such a software suite will include individual VCSELs, VCSEL arrays, high-power/brightness VECSELs, better performing semiconductor optical amplifiers (SOAs), higher slope efficiency edge emitters (both single mode, broad area and diode bars) etc. Existing semiconductor material technologies for the 3-5 µm mid infrared range are severely limited by low gain, high losses, poor beam quality, low wall-plug efficiencies and, often, the need to operate at cryogenic temperatures. An approach to avoid many of these problems may be found by adding small amounts of bismuth to the conventional 3-5 micron materials. The mid-IR laser software design development has several potential applications to IRCM, ISR (Intelligence, Surveillance, Reconnaissance): LADAR, 3-D imaging, active illumination imaging in the mid-wave IR requiring sources that operate as efficiently as possible and at Watt power levels.

Keywords:
semiconductor epitaxy, gain, intrinsic losses, software tools

The objective of this STTR is to determine the potential of the novel III-V-Bi material system for laser applications for the 3-5µm window with the potential of watt-level powers for Air Force applications. This wavelength range is currently inadequately served for CW operation at room temperature by three challenging technologies: i) quantum cascade lasers (QCL), interband cascade lasers (ICL) and AlInGaAsSb based type-I quantum well lasers. The III-V-Bi material can potentially achieve better performance in the full 3-5µm regime. Incorporating dilute amounts of Bi atoms in the host material strongly reduces the bandgap extending the accessible wavelength range over existing systems. Also, interaction between Bi-atoms and the host matrix modifies the bandstructure and the density of states of the host material. It changes the hole effective mass, modifies the internal strain, changes the spin-off splitting, perturbs the Bloch character of states and can introduce gaps in the valence-band structure. This could potentially allow for drastic reductions of the Auger and intraband absorption losses that limit the performance of existing lasers. Large scale density functional (DFT) simulations will be employed to extract critical bandstructure parameters and an interface built to input these into Nonlinear Control Strategies SimuLaseTM semiconductor epitaxial design software.

Benefits:
The strong demand for high quality semiconductor laser systems for dual-use technologies that must satisfy stringent military specifications as well as future state-of-the-art commercial applications, creates a critical need for a commercial software package that can leverage a cost effective, fast track to the final laser product. Future improvements in semiconductor wafer growth quality will require the implementation of improved wafer processing diagnostics during in-situ growth within MBE and MOCVD systems. For example, state-of-the-art MBE growth systems contain multiple chambers designed to carry out wafer diagnostics during material growth. Future markets for such a software suite will include individual VCSELs, VCSEL arrays, high-power/brightness VECSELs, better performing semiconductor optical amplifiers (SOAs), higher slope efficiency edge emitters (both single mode, broad area and diode bars) etc. Existing semiconductor material technologies for the 3-5 µm mid infrared range are severely limited by low gain, high losses, poor beam quality, low wall-plug efficiencies and, often, the need to operate at cryogenic temperatures. An approach to avoid many of these problems may be found by adding small amounts of bismuth to the conventional 3-5 micron materials. The mid-IR laser software design development has several potential applications to IRCM, ISR (Intelligence, Surveillance, Reconnaissance): LADAR, 3-D imaging, active illumination imaging in the mid-wave IR requiring sources that operate as efficiently as possible and at Watt power levels.

Keywords:
density functional theory, quantum cascade laser, band anti-crossing, photo luminescence, Vienna Ab initio Simulation Package, molecular beam epitaxy, Epitaxial design software, Bismide