M. Diagne

Resonant-cavity InGaN quantum-well blue light-emitting diodes

We describe progress in blue resonant-cavity light-emitting diodes, based on InGaN/GaN quantum-well heterostructures. We have fabricated vertical-microcavity devices in which either one or both mirrors forming the cavity are patterned, high-reflectivity dielectrics Bragg reflectors. The results suggest that a blue vertical-cavity diode laser may be feasible by this approach.

A quasicontinuous wave, optically pumped violet vertical cavity surface emitting laser

We have fabricated and studied a violet (λ=403 nm) vertical cavity surface emitting laser structure, composed of an InGaN multiple quantum well active medium and a pair of high reflectivity dielectric mirrors. Lasing under high repetition rate (76 MHz) pulsed optical pumping has been achieved at temperatures up to T=258 K at average pump power of approximately 30 mW.

Vertical cavity violet light emitting diode incorporating an aluminum gallium nitride distributed Bragg mirror and a tunnel junction

We have designed and implemented a vertical cavity violet light emitting diode which features an optical resonator composed of an in situ grown GaN/AlGaN DBR and a high reflectivity dielectric mirror. The active InGaN MQW medium is grown directly atop the AlGaN DBR and the structure includes an intracavity lateral current spreading layer based on a p++/n++ InGaN/GaN tunnel junction. Electroluminescence shows directional emission, with modal linewidths as narrow as 0.6 nm.

A vertical cavity light emitting InGaN quantum well heterostructure

A method is described for fabricating a vertical cavity light emitting structure for nitride semiconductors. The process involves the separation of a InGaN/GaN/AlGaN quantum well heterostructure from its sapphire substrate an its enclosure by a pair of high reflectivity, low loss dielectric mirrors to define the optical resonator. We have demonstrated a cavity Q factor exceeding 600 in initial experiments, suggesting that the approach can be useful for blue and near ultraviolet resonant cavity light emitting diodes and vertical cavity lasers.

A vertical injection blue light emitting diode in substrate separated InGaN heterostructures

A vertical injection, light emitting InGaN quantum well diode has been demonstrated by separating the nitride heterostructure from its sapphire substrate by ultraviolet laser photoablation within a process scheme that allows transferring the devices to a host substrate. The incorporation of a dielectric multilayer stack to the device is shown to be a first practical step towards a resonant cavity light emitting diode.

A Matrix Addressable 1024 Element Blue Light Emitting InGaN QW Diode Array

We have fabricated a 32 x 32 two-dimensional proof-of-concept array of individually matrix addressable blue InGaN MQW LEDs. Each 30 μm diameter element is equipped with its own integrated microlens, making these types programmable arrays potentially useful as sources for proximity microscopy with high parallel throughput such as in spatially resolved fluorescence spectroscopic imaging applications.

A high injection resonant cavity violet light emitting diode incorporating (Al, Ga)N distributed bragg reflector

A vertical cavity violet LED has been designed and implemented which includes an optical resonator composed of an in-situ grown GaN/AlGaN DBR and a high reflectivity dielectric mirror. The structure incorporates an intracavity lateral current spreading layer based on a p ++ /n ++ InGaN/GaN tunnel junction. Electroluminescence shows directional emission, with modal line-widths as narrow as 0.6 nm.

GaN-based tunnel junction in optical devices

We have demonstrated hole injection through a tunnel junction embedded in the GaN-based light emitting diode structure. The tunnel junction consists of 30 nm GaN:Si++ and 15 nm InGaN:Mg++ grown on a GaN-InGaN quantum well heterostructure. The forward voltage of the light emitting diode, included the voltage drop across the reverse-biased tunnel junction, is 4.1 V at 50 Z/cm

Near ultraviolet optically pumped vertical cavity laser

_2), while that of a standard light emitting diode with a conventional contact structure is 3.5 V. The light output of the diode with the tunnel junction is comparable to that of the standard device. We then employed the tunnel junction in vertical cavity surface emitting laser structures and dual-wavelength light emitters. In the vertical cavity structure, a good lateral current spreading was accomplished, resulting in uniform emission pattern. The dual-wavelength light emitter has been operated as a three- terminal device with independent electrical control of each LEDs to a nsec time scale.