Optical switching in midinfrared light-emitting diodes

Many types of optical switching devices have been studied and demonstrated using nonlinear effects in a variety of semiconductor materials and more recently in optical fibers. Light-controlled switches have a wide variety of potential applications in optical communications and high-speed optoelectronic systems. Optically controlled, fiber-based switches such as loop mirrors or soliton gates can be very fast with good contrast ratios, low-power, and cascadable Boolean logic, but they are difficult to arrange in arrays and integrate with electronics. Although such components are commonplace in the visible and near infrared (,1.55 mm), there have to date been inadequate reports of optical switching in the midinfrared spectral region ~2–5 mm!. In this letter, we report on the optical quenching of midinfrared electroluminescence at 3.0 mm, which could form the basis of a midinfrared optical switch The light-emitting diode ~LEDs! were fabricated from III-V double heterostructures ~DHs! grown by liquid phase epitaxy ~LPE!. A conventional horizontal, graphite sliding boat was used for the LPE growth of the LED structures onto p-type InAs ~100! substrates. These were 14 mm314 mm square with a carrier concentration of ;1310 cm and were obtained from Wafer Technology Ltd. Epitaxy was carried out with the graphite boat inside a high purity quartz reactor tube under flowing ultrapure hydrogen gas provided from a Pd-diffusion unit. The apparatus was fully automated and controlled with LABVIEW operating software from a personal computer. The resulting epitaxial structure, which has been described in detail previously elsewhere, was a DH in which the unintentionally doped n-InAs active layer is enclosed between pand n-InAs0.42Sb0.18P0.40 confinement layers. The P content in the confinement layers was 0.40 ~Eg 5640 meV and T54 K! to provide large interface band offsets DEc5151 meV and DEv521 meV for good carrier confinement. The InAs active region ~Eg5415 meV and T 54 K! was 0.7 mm thick, and the InAs0.42Sb0.18P0.40 layers were isoperiodic with InAs, each being 3.0 mm in thickness. By using Yb rare-earth gettering, the residual carrier concen-