James M. DePuydt

Bio: James M. DePuydt is an academic researcher from 3M. The author has contributed to research in topics: Molecular beam epitaxy & Laser diode. The author has an hindex of 19, co-authored 33 publications receiving 2580 citations. Previous affiliations of James M. DePuydt include Philips & University of Florida.

Blue-green laser diode

Abstract: A II-VI compound semiconductor laser diode (10) is formed from overlaying layers of material including an n-type single crystal semiconductor substrate (12), adjacent n-type and p-type guiding lasers (14) and (16) of II-VI semiconductor forming a pn junction, a quantum well active layer (18) of II-VI semiconductor between the guiding layers (14) and (16), first electrode (32) opposite the substrate (12) from the n-type guiding layer (14), and a second electrode (30) opposite the p-type guiding layer (16) from the quantum well layer (18) Electrode layer (30) is characterized by a Fermi energy A p-type ohmic contact layer (26) is doped, with shallow acceptors having a shallow acceptor energy, to a net acceptor concentration of at least 1 x 1017 cm-3, and includes sufficient deep energy states between the shallow acceptor energy and the electrode layer Fermi energy to enable cascade tunneling by charge carriers

Degradation of II‐VI based blue‐green light emitters

Abstract: We have carried out the first detailed structural studies of degradation in II‐VI blue‐green light emitters Electroluminescence and transmission electron microscopy studies carried out on light emitting diodes fabricated from quantum well laser structures and electroluminescence studies on stripe laser structures show that degradation occurs by the formation and propagation of crystal defects The studies indicate that room temperature cw lasing in such structures is possibly prevented by the rapid formation of such defects at the high current densities required for lasing

Role of stacking faults as misfit dislocation sources and nonradiative recombination centers in II‐VI heterostructures and devices

Abstract: We have investigated the role of stacking faults in high quality ZnSxSe1−x heterostructures and a ZnSxSe1−x/CdxZn1−xSe based II‐VI blue‐green quantum well laser structure grown on GaAs substrates. We find that these stacking faults, which originate at the epilayer/substrate interface during the initial stages of the growth, act as sources for misfit dislocation formation in the quantum well region of ZnSxSe1−x/CdxZn1−xSe based devices. We have analyzed the formation mechanism of these dislocations. We also show through cathodoluminescence microscopy that these stacking faults act as nonradiative recombination centers which therefore reduce the luminescence of these devices.

Low-threshold buried-ridge II-VI laser diodes

Abstract: Blue‐green (λ=511 nm) separate confinement laser structures based on lattice‐matched MgZnSSe‐ZnSSe‐CdZnSe have been grown by molecular beam epitaxy. Wide stripe gain‐guided devices have been fabricated from several such wafers. These devices exhibit room‐temperature pulsed threshold current densities as low as 630 A/cm2 and threshold voltages less than 9 V. Using a novel self‐aligned process that results in a planar surface, buried‐ridge laser diodes have also been fabricated. These devices have demonstrated room‐temperature threshold currents as low as 2.5 mA, which is more than a factor of 50 lower than that of any previously reported II‐VI laser diode. Room‐temperature operation at duty factors up to 50% has been demonstrated. The far‐field patterns from these devices indicate single lateral mode operation, suitable for diffraction‐limited applications, such as optical data storage.

Growth of II VI laser diodes with quantum wells by atomic layer epitaxy and migration enhanced epitaxy

Abstract: A method for using atomic layer epitaxy (ALE) and/or migration enhanced epitaxy (MEE) to grow high efficiency quantum wells in II-VI laser diodes. The substrate and previously grown layers of the laser diode are heated to a temperature less than or equal to about 200° C. in an MBE chamber. Sources of Cd, Zn, and Se are injected alternately into the chamber to grow a short-period strained-layer superlattice (SPSLS) quantum well layer including overlaying monolayers of Cd, Zn and Se. The quantum well layer is described by the notation [(CdSe) m (ZnSe) n ] p where m, n and p are integers.

Room-temperature ultraviolet nanowire nanolasers

Abstract: Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated The self-organized, oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process These wide band-gap semiconductor nanowires form natural laser cavities with diameters varying from 20 to 150 nanometers and lengths up to 10 micrometers Under optical excitation, surface-emitting lasing action was observed at 385 nanometers, with an emission linewidth less than 03 nanometer The chemical flexibility and the one-dimensionality of the nanowires make them ideal miniaturized laser light sources These short-wavelength nanolasers could have myriad applications, including optical computing, information storage, and microanalysis

Candela‐class high‐brightness InGaN/AlGaN double‐heterostructure blue‐light‐emitting diodes

Abstract: Candela‐class high‐brightness InGaN/AlGaN double‐heterostructure (DH) blue‐light‐emitting diodes(LEDs) with the luminous intensity over 1 cd were fabricated As an active layer, a Zn‐doped InGaN layer was used for the DH LEDs The typical output power was 1500 μW and the external quantum efficiency was as high as 27% at a forward current of 20 mA at room temperature The peak wavelength and the full width at half‐maximum of the electroluminescence were 450 and 70 nm, respectively This value of luminous intensity was the highest ever reported for blue LEDs

Large‐band‐gap SiC, III‐V nitride, and II‐VI ZnSe‐based semiconductor device technologies

Abstract: In the past several years, research in each of the wide‐band‐gap semiconductors, SiC, GaN, and ZnSe, has led to major advances which now make them viable for device applications. The merits of each contender for high‐temperature electronics and short‐wavelength optical applications are compared. The outstanding thermal and chemical stability of SiC and GaN should enable them to operate at high temperatures and in hostile environments, and also make them attractive for high‐power operation. The present advanced stage of development of SiC substrates and metal‐oxide‐semiconductor technology makes SiC the leading contender for high‐temperature and high‐power applications if ohmic contacts and interface‐state densities can be further improved. GaN, despite fundamentally superior electronic properties and better ohmic contact resistances, must overcome the lack of an ideal substrate material and a relatively advanced SiC infrastructure in order to compete in electronics applications. Prototype transistors have been fabricated from both SiC and GaN, and the microwave characteristics and high‐temperature performance of SiC transistors have been studied. For optical emitters and detectors, ZnSe, SiC, and GaN all have demonstrated operation in the green, blue, or ultraviolet (UV) spectra. Blue SiC light‐emitting diodes (LEDs) have been on the market for several years, joined recently by UV and blue GaN‐based LEDs. These products should find wide use in full color display and other technologies. Promising prototype UV photodetectors have been fabricated from both SiC and GaN. In laser development, ZnSe leads the way with more sophisticated designs having further improved performance being rapidly demonstrated. If the low damage threshold of ZnSe continues to limit practical laser applications, GaN appears poised to become the semiconductor of choice for short‐wavelength lasers in optical memory and other applications. For further development of these materials to be realized, doping densities (especially p type) and ohmic contact technologies have to be improved. Economies of scale need to be realized through the development of larger SiC substrates. Improved substrate materials, ideally GaN itself, need to be aggressively pursued to further develop the GaN‐based material system and enable the fabrication of lasers. ZnSe material quality is already outstanding and now researchers must focus their attention on addressing the short lifetimes of ZnSe‐based lasers to determine whether the material is sufficiently durable for practical laser applications. The problems related to these three wide‐band‐gap semiconductor systems have moved away from materials science toward the device arena, where their technological development can rapidly be brought to maturity.

InGaN-Based Multi-Quantum-Well-Structure Laser Diodes.

Abstract: InGaN multi-quantum-well (MQW) structure laser diodes (LDs) fabricated from III-V nitride materials were grown by metalorganic chemical vapor deposition on sapphire substrates. The mirror facet for a laser cavity was formed by etching of III-V nitride films without cleaving. As an active layer, the InGaN MQW structure was used. The InGaN MQW LDs produced 215 mW at a forward current of 2.3 A, with a sharp peak of light output at 417 nm that had a full width at half-maximum of 1.6 nm under the pulsed current injection at room temperature. The laser threshold current density was 4 kA/cm2. The emission wavelength is the shortest one ever generated by a semiconductor laser diode.

Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO

Abstract: Since the successful demonstration of a blue light-emitting diode (LED)1, potential materials for making short-wavelength LEDs and diode lasers have been attracting increasing interest as the demands for display, illumination and information storage grow2,3,4. Zinc oxide has substantial advantages including large exciton binding energy, as demonstrated by efficient excitonic lasing on optical excitation5,6. Several groups have postulated the use of p-type ZnO doped with nitrogen, arsenic or phosphorus7,8,9,10, and even p–n junctions11,12,13. However, the choice of dopant and growth technique remains controversial and the reliability of p-type ZnO is still under debate14. If ZnO is ever to produce long-lasting and robust devices, the quality of epitaxial layers has to be improved as has been the protocol in other compound semiconductors15. Here we report high-quality undoped films with electron mobility exceeding that in the bulk. We have used a new technique to fabricate p-type ZnO reproducibly. Violet electroluminescence from homostructural p–i–n junctions is demonstrated at room-temperature.