J.A. Lott

Efficient room-temperature continuous-wave AlGaInP/AlGaAs visible (670 nm) vertical-cavity surface-emitting laser diodes

Significant improvement in the performance of AlGaInP/AlGaAs visible vertical-cavity surface-emitting laser diodes has been achieved in gain-guided planar-geometry devices utilizing proton implants to define the current injection path. Threshold currents as low as 1.25 mA were measured on 10 /spl mu/m-diameter devices, with maximum power output of 0.33 mW from larger devices. Continuous-wave (cw) lasing was achieved at temperatures as high as 45/spl deg/C. The improved diode performance is attributed to better lateral heat-sinking and reduced parasitic heat generation afforded by the planar device structure, relative to previously-reported air-post structures. This work represents the first realization of efficient room-temperature operation of AlGaInP-based visible VCSEL diodes.<<ETX>>

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.<<ETX>>

MOVPE growth of InAlGaP-based visible vertical-cavity surface-emitting lasers

Abstract Materials growth issues for visible vertical-cavity surface-emitting lasers have been addressed in detail. For high optical efficiency in the laser cavity, the optical properties of In 0.48 (Al y Ga 1- y ) 0.52 P quarternary alloys lattice-matched to GaAs were optimized as a function of MOVPE growth parameters including substrate temperature and misorientation. The narrowest photoluminescent linewidths yet reported for all of the direct bandgap In(Al y Ga 1- y )P alloys (0⩽ y ⩽0.5) were observed, including 4.2 meV for InGaP. The growth and optical properties of strained quantum well structures were then investigated for use in the laser active region. Structures with a broad range of well and barrier compositions and thicknesses were prepared, and characterized using low-temperature photoluminescence. Based upon this work, high-optical quality strained and unstrained multiple-quantum-well heterostructures were grown for use in the 640–670 nm wavelength range. Epitaxial multilayer dielectric mirror stacks reflecting at visible (620–700 nm) wavelengths were fabricated from the Al 0.5 Ga 0.5 As/AlAs and InGaP/InAlP systems, and for both types of mirrors excellent reflectivity characteristics were observed. Visible VCSEL structures were grown for photopumping experiments, and the structures exhibited low threshold powers. Wavelength of operation of these structures was in the range 632–661nm.

InAIP/InAlGaP distributed Bragg reflectors for visible vertical cavity surface‐emitting lasers

Distributed Bragg reflectors (DBRs) composed of In0.5Al0.5P/In0.5(AlyGa1−y)0.5P quarter‐wave layers have been prepared using metalorganic vapor phase epitaxy. The structures were grown over a wide range of high‐index layer composition (0≤y≤0.6) and peak reflectivity wavelength (720 nm≤λ≤565 nm, covering the spectrum from deep red to green). In all cases observed and calculated reflectance spectra were in excellent agreement. Using these DBRs, an undoped all‐phosphide visible vertical cavity surface‐emitting laser structure was grown. Under pulsed optical excitation at room temperature, lasing was obtained at a wavelength of λ∼670 nm, with a threshold power density comparable to that observed from similar structures prepared using AlAs/AlGaAs DBRs.

Cavity design for improved electrical injection in InAlGaP/AlGaAs visible (639–661 nm) vertical‐cavity surface‐emitting laser diodes

A novel optical cavity design for improved electrical injection in visible vertical‐cavity surface‐emitting laser (VCSEL) diodes employing an InGaP/InAlGaP strained quantum‐well active optical cavity and AlAs/Al0.5Ga0.5As distributed Bragg reflectors (DBRs) is described. The cavity design was determined by measuring the lasing threshold current density of visible edge‐emitting laser diodes with AlAs/Al0.5Ga0.5As DBR cladding layers. By inserting InAlP spacer layers between the active region and the DBR cladding, significant improvement in the performance of the edge‐emitting lasers was achieved. This approach was then applied to the design of visible VCSEL diodes, and resulted in the first demonstration of room‐temperature electrically injected lasing, over the wavelength range 639–661 nm. The visible VCSELs, with a diameter of 20 μm, exhibit pulsed output power of 3.4 mW at 650 nm, and continue to lase at a duty cycle of 40%. The threshold current was 30 mA, with a low threshold voltage (2.7 V) and low series resistance (<15 Ω).A novel optical cavity design for improved electrical injection in visible vertical‐cavity surface‐emitting laser (VCSEL) diodes employing an InGaP/InAlGaP strained quantum‐well active optical cavity and AlAs/Al0.5Ga0.5As distributed Bragg reflectors (DBRs) is described. The cavity design was determined by measuring the lasing threshold current density of visible edge‐emitting laser diodes with AlAs/Al0.5Ga0.5As DBR cladding layers. By inserting InAlP spacer layers between the active region and the DBR cladding, significant improvement in the performance of the edge‐emitting lasers was achieved. This approach was then applied to the design of visible VCSEL diodes, and resulted in the first demonstration of room‐temperature electrically injected lasing, over the wavelength range 639–661 nm. The visible VCSELs, with a diameter of 20 μm, exhibit pulsed output power of 3.4 mW at 650 nm, and continue to lase at a duty cycle of 40%. The threshold current was 30 mA, with a low threshold voltage (2.7 V) and low s...

Metalorganic vapor phase epitaxial growth of red and infrared vertical-cavity surface-emitting laser diodes

Abstract Metalorganic vapor phase epitaxy (MOVPE) is used for the growth of vertical-cavity surface-emitting laser (VCSEL) diodes. MOVPE exhibits a number of important advantages over the more commonly-used molecular-beam epitaxial (MBE) techniques, including ease of continuous compositional grading and carbon doping for low-resistance p-type distributed Bragg reflectors (DBRs), higher growth rates for rapid throughput and greater versatility in choice of materials and dopants. Planar gain-guided red VCSELs based on AlGaInP/AlGaAs heterostructures lase continuous-wave at room temperature, with voltage thresholds between 2.5 and 3 V and maximum power outputs of over 0.3 mW. Top-emitting infra-red (IR) VCSELs exhibit the highest power-conversion (wall-plug) efficiencies (21%), lowest threshold voltage (1.47 V), and highest single mode power (4.4 mW from an 8 μm device) yet reported. These results establish MOVPE as a preferred growth technique for this important new family of photonic devices.

Excitonic transitions in InGaP/InAlGaP strained quantum wells

Excitonic transitions in metalorganic vapor phase epitaxially grown InxGa1−xP/In0.48(Al0.7Ga0.3)0.52P strained single quantum‐well structures are characterized using low‐temperature photoluminescence and photoluminescence excitation (PLE) spectroscopies. The structures consist of several uncoupled quantum wells with thicknesses between 1.2 and 11.3 nm, and compositions x of 0.48 (nominally lattice matched) and 0.56 (∼0.6% biaxial compressive strain). The photoluminescence spectra exhibit intense peaks over the wavelength range 550–650 nm, with linewidths between 7 and 23 meV depending on the well thickness. The PLE spectra reveal strong heavy‐hole and light‐hole transitions, as well as higher‐order (n=2) transitions in the thicker wells. The heavy‐hole/light‐hole splitting shows little dependence on well thickness in the strained structures, indicating a relatively large conduction band offset of ΔEC∼0.75ΔEG.

Wavelength dependence of the threshold in an InGaP‐InAlGaP vertical cavity surface emitting laser

The wavelength dependence of the threshold in an InGaP‐InAlGaP vertical cavity surface emitting laser is investigated using a microscopic theory of the semiconductor gain medium. Good agreement is found between experiment and theory for the minimum threshold lasing wavelength for a range of laser structures.

Formation of high resistivity regions in p-type Al0.5In0.5P by ion implantation

Ion implantation has been applied to magnesium‐doped Al0.5In0.5P to produce high resistivity regions for the first time. Hydrogen, oxygen, and argon ions were implanted at a base dose ranging from 5×1012 to 5×1014 cm−2 and annealed from 400 to 900u2009°C. Hydrogen did not appreciably compensate the In0.5Al0.5P layer while oxygen and argon produced sheet resistances up to 1×109 Ω/⧠. After annealing at 800u2009°C, regions with high dose oxygen implants maintained a sheet resistance above 1×107 Ω/⧠, while regions with high dose argon implants recovered most of the unimplanted conductivity.