Amethyst Research (United Kingdom)

The high-quality growth of midwave infrared light emitters on silicon substrates will advance their incorporation into photonic integrated circuits, and also introduce manufacturing advantages over conventional devices grown on lattice-matched GaSb. Here we report interband cascade light emitting devices (ICLEDs) grown on 4 degree offcut silicon with 12% lattice mismatch. Four wafers produced functioning devices, with variations from wafer to wafer but uniform performance of devices from a given wafer. The full width at half maxima for the (004) GaSb rocking curves were as narrow as ∼ 163 arc seconds, and the root mean square surface roughness as small as 3.2 nm. Devices from the four wafers, as well as from a control structure grown to the same design on GaSb, were mounted epitaxial-side-up (epi-up). While core heating severely limited continuous wave (cw) emission from the control devices at relatively modest currents, efficient heat dissipation via the substrate allowed output from the devices on silicon to increase up to much higher currents. Although the devices on silicon had higher leakage currents, probably occurring primarily at dislocations resulting from the lattice-mismatched growth, accounting for differences in architecture the efficiency at high cw current was approximately 75% of that of our previous best-performing standard epi-down ICLEDs grown on GaSb. At 100 mA injection current, 200-µm-diameter mesas produced 184 µW of cw output power when operated at T = 25 °C, and 140 µW at 85°C. Epi-up mid-IR light emitters grown on silicon will be far simpler to process and much less expensive to manufacture than conventional devices grown on GaSb and mounted epi-down.

A study of certain defects in GaInNAs, and their passivation. The passivation process could lead to more efficient photovoltaic devices.

Although formal planning procedures are key parts of military doctrine, they may not be well suited to highly dynamic, time-pressured environments. The authors describe an intuitive planning process developed as an alternative to the procedure used by the Canadian Forces (CF). The Intuitive Operational Planning Process (IOPP) treats planning as a highly iterative process of incremental refinement in which a single course of action is elaborated and continually evaluated for its suitability. To examine the effectiveness of the IOPP, 12 members of a reserve CF Civil Military Cooperation unit of Land Force Central Area acted as planning staffs and created plans for two simulated planning exercises. Participants employed the IOPP for one scenario and the existing CF Operational Planning Process (OPP) for another. The teams were able to successfully employ the IOPP to develop acceptable plans; however, it was not possible to determine statistically that the quality of these plans surpassed that of plans generated with the OPP because of limitations of the data set. The IOPP was judged to be very easy to use, but teams expressed less trust in it than the existing OPP. The IOPP may foster greater collaboration and commander involvement in planning than the OPP.

Reverse current in diodes can be dominated by generation processes, depending exponentially on temperature according to the rate-limiting step in the generation process. In this report, the current-voltage-temperature (IVT) relationship is analyzed for several midwave infrared and long-wave infrared (MWIR x = 0.295, LWIR x = 0.233) Hg 1-x cd x Te (MCT) diodes. The energy varied from diode to diode. At high reverse biases, the energy tends toward the band gap energy. Close to zero bias, the energy ranged from 0.06 to 0.1 eV. Deep level transient spectroscopy (DLTS) showed a broad peak centered at 55-80 K for the MWIR MCT. Comparison of the DLTS spectrum to a simulation based on the energy and capture cross section from a rate window analysis shows that the peak is a band of traps. The capacitance transient amplitude increased as the filling pulse increased from 1 μs to 0.1 s, consistent with capture at a dislocation. A shift to lower temperatures for the peak was also observed when the diodes are cooled under forward bias. The shift is reversible, indicating that the traps consist at least partially of a bistable defect.