Cavity Light-emitting Diodes Research Articles

Temperature characteristics of near-infrared (1.7 micron), resonant cavity light-emitting diodes

The design and operation of a near infra-red resonant cavity light-emitting diode operating at 1.7 microns with a 16 nm linewidth is described. The structure is based on a wafer-bonded combination of InGaAs/InAlAs/InP quantum well emitter and an AlAs/GaAs distributed Bragg reflector. Detailed temperature characteristics over a range from 80 to 373 K are presented. The temperature dependence of the main cavity mode emission wavelength is shown to be 0.15 nm/K. The intensity is found to increase with temperature from 80 to 325 K and thereafter decrease. There is a 20 degree range in which the intensity is constant within approximately 5%. A model is suggested for this behaviour.

Angular spectrum of visible resonant cavity light-emitting diodes

We present spectrally resolved angular radiation patterns from visible resonant cavity light-emitting diodes. Recording the pattern for a fixed wavelength clearly demonstrates how the overall angular emission is strongly influenced by the relative spectral alignment of the cavity resonance and the underlying quantum well emission, i.e., the detuning. Combined with measurements of total optical power, taken over a range of solid angles, the results highlight the importance of accounting for the collection optics of a proposed application when an optimum design is considered.

Solid source molecular beam epitaxy growth and characterization of resonant cavity light-emitting diodes

We report on the solid source molecular beam epitaxy growth (SSMBE) of resonant cavity light-emitting diodes (RCLED) operating at 660 and 1300 nm wavelengths using valved cracking cells. The 1300 nm RCLED reported here is according to the best of the author's knowledge the first monolithic RCLED made on that wavelength. The performance characteristics of the grown devices show that SSMBE is a viable growth method for complex vertical cavity structures.

Light-emitting diodes with 31% external quantum efficiency by outcoupling of lateral waveguide modes

The external quantum efficiency of light-emitting diodes (LEDs) is usually limited by total internal reflection at the semiconductor–air interface. This problem can be overcome by a combination of light scattering at a textured top surface and reflection on a backside mirror. With this design, we achieve 22% external quantum efficiency. One of the main loss mechanisms in such nonresonant cavity (NRC) light-emitting diodes is coupling into an internal waveguide. Texturing the surface of this waveguide allows the partial extraction of the confined light. In this way, we demonstrate an increase in the external quantum efficiency of NRC-LEDs to 31%.

InP-based 1.55 µm resonant cavity light-emitting diode with two epitaxial mirrors

We report on the fabrication and characterisation of a resonant cavity light-emitting diode (RCLED) operating at 1.55 µm. As compared to conventional LEDs such devices merit from a higher emission intensity with a more narrow linewidth and are therefore promising as light sources in fibre optical communication systems. The present design is based on an InGaAsP multi-quantum well structure and utilises two InGaAsP/InP epitaxial distributed Bragg reflectors (DBRs), one 50 periods high reflectivity bottom mirror and a top out-coupling mirror with lower reflectivity. This gives the advantage of top-emission combined with the possibility of achieving very narrow linewidth. The process is fully monolithic and full wafer scale compatible.

Light-emitting diodes with 17% external quantum efficiency at 622 Mb/s for high-bandwidth parallel short-distance optical interconnects

We report on nonresonant cavity light-emitting diodes (NRC-LED) with large quantum efficiencies and high speed. A maximum quantum efficiency of 31% is measured for a device with an active layer thickness of 120 nm, and 18.7% for a device having an active layer of 30 nm. Further, we report on optical rise and fall times of NRC-LEDs. Even when switched to current levels below 4 mA, at which the external quantum efficiency exceeds 17%, our NRC-LEDs have 10%-90% rise and fall times of less than 2 ns. As a result, eye diagrams taken at this current level at 622 Mb/s are wide open. This demonstrates the suitability of high-efficiency NRC-LEDs for optical interconnects. Finally, from a system's viewpoint it is important to note that the optical output power of NRC-LEDs decreases by only 0.36%//spl deg/C.

Monolithic super-bright red resonant cavity light-emitting diode grown by solid source molecular beam epitaxy

Monolithic super-bright resonant-cavity light-emitting diode operating at /spl lambda/=663 nm has been developed. The diode consisted of a 1/spl lambda/-thick AlGaInP active region sandwiched between AlAs-AlGaAs distributed Bragg reflectors. The device structure was grown by solid source molecular beam epitaxy. The current aperture of the emitter was created by lateral selective wet thermal oxidation. A record-high peak wall-plug efficiency of 2.2% and a continuous-wave output power of 1.4 mW were attained without heatsinking at room temperature from a diode having a diameter of 80 μm. The emission linewidth was as narrow as 4.5 nm.

AlGaInP visible resonant cavity light-emitting diodes

Visible (670-nm) resonant cavity light-emitting diodes (RCLEDs) composed entirely of AlGaInP alloys are discussed. The devices consist of a strained quantum well optical cavity active region surrounded by AlInP/(AlGa)InP distributed Bragg reflectors (DBRs). The bottom DBR is a 60.5 period high reflector while the top partial reflector, which determines the emission linewidth, is a five-period output coupling DBR with a reflectance of about 57%. The devices exhibit linewidths of 4.8 nm (13.3 meV) at 300 K and are promising for plastic fiber communication systems and monochromatic displays. >

Visible (660 nm) resonant cavity light-emitting diodes

The demonstration of the first visible resonant cavity light-emitting diodes (RCLEDs) is reported. The devices consist of an InAlGaP strained quantum well active region surrounded by AlAs/AlGaAs distributed Bragg reflectors. Linewidths from 0.9 nm (2.6 meV) to 45 nm (12.8 meV) were obtained by varying the cavity quality factor (Q).

Resonant cavity light-emitting diode

A novel concept of a light-emitting diode (LED) is proposed and demonstrated in which the active region of the device is placed in a resonant optical cavity. As a consequence, the optical emission from the active region is restricted to the modes of the cavity. Resonant cavity light-emitting diodes (RCLED) have higher spectral purity and higher emission intensity as compared to conventional light emitting diodes. Results on a top-emitting RCLED structure with AlAs/AlxGa1−xAs quarter wave mirrors grown by molecular beam epitaxy are presented. The experimental emission linewidth is 17 meV (0.65 kT) at room temperature. The top-emission intensity is a factor of 1.7 higher as compared to conventional LEDs.