Dilute nitride resonant-cavity light emitting diode

Resonant cavity LEDs (RCLEDs) are a viable and low-cost alternative light source to lasers for optical communication systems in the 1.3 µm O-band. Most work in this area has been conducted on InP-based material, which is inherently costly, devices often require cooling and the refractive index contrast for constructing mirrors is low. Here, we demonstrate a high-performance GaAs-based RCLED using a dilute nitride GaInNAs active layer emitting in the 1.3 μm wavelength window. While previous 1.3 µm RCLEDs have used metallic mirrors on the back of the device, we exploit the high refractive index contrast of the GaAs/AlAs system to place Distributed Bragg mirrors on both sides of the active layer and achieve superior performance. The external quantum efficiency of the devices is 20% and the full width at half maximum of the emission spectrum is 5.2 nm at room temperature, into a narrow angular cone. The emission power from an 88 μm diameter aperture is 0.5 mW, which, together with the narrow spectral linewidth, makes the device suitable for deployment in a coarse Wavelength Division Multiplexing (WDM) communications system

Effects of Thermal Annealing and Selective Chemical Etching on Structural and Optical Properties of GaAsBi Epilayer with Droplet Systems

A GaAs1-xBix layer was grown by molecular beam epitaxy (MBE) with a low Bi content (2.3%) on GaAs maintaining the substrate at a non-rotating state and was then annealed at 750 degrees C, 800 degrees C and 850 degrees C. Each sample that was covered with droplets was investigated by using the Atomic Force Microscopy (AFM), Electrostatic Force Microscopy (EFM) and Photoluminescence (PL) techniques. The surface properties of the GaAs1-xBix layer were investigated by AFM and observed to have a droplet system, which was composed of a donut and a tail. The optical quality of the samples was enhanced after thermal annealing up to 800 degrees C, and the maximum PL intensity was obtained at 750 degrees C. AFM images revealed that the shape of the droplet and tail changed with increasing annealing temperature. EFM images revealed a phase separation on the surface droplet system. To explore the nature of the droplets, previously claimed to be made of Ga and/or Bi, and their effect on PL spectrum, a chemical etch procedure was carried out by using diluted solutions of H2SO4 and/or HCl. We showed that droplets may be efficiently removed from the surface, and PL intensity could be improved by using a proper sequence of chemical etching procedures. Furthermore, the presence of two different phases for the droplet-system observed by EFM was also confirmed by the selective etching procedure