Cleaved-facet violet laser diodes with lattice-matched Al0.82In0.18N/GaN multilayers as n-cladding

Electrically injected, edge-emitting cleaved-facet violet laser diodes were realized using a 480 nm thick lattice matched Si doped Al0.82In0.18N/GaN multilayer as the cladding on the n-side of the waveguide. Far-field measurements verify strong mode confinement to the waveguide. An extra voltage is measured and investigated using separate mesa structures with a single AlInN insertion. This showed that the electron current has a small thermally activated shunt resistance with a barrier of 0.135 eV and a current which scales according to V-n, where n similar to 3 at current densities appropriate to laser operation. (C) 2011 American Institute of Physics. (doi:10.1063/1.3589974

Red-Emitting III-Nitride Self-Assembled Quantum Dot Lasers.

Visible and ultra-violet light sources have numerous applications in the fields of solid state lighting, optical data storage, plastic fiber communications, heads-up displays in automobiles, and in quantum cryptography and communications. Most research and development into such sources is being done using III-nitride materials where the emission can be tuned from the deep UV in AlN to the near infrared in InN. However due to material limitations including large strain, piezoelectric polarization, and the unavailability of cheap native substrates, most visible devices are restricted to emission near GaN at 365nm up to around 530nm. These dots are formed by the relaxation of strain, and it has been shown both theoretically and experimentally that the piezoelectric field and the resultant quantum confined stark effect are significantly lower than those values reported in comparable QWs. As a result, the radiative carrier lifetimes in such dots are typically around 10-100 times smaller than those in equivalent QWs. Furthermore, the quasi-three dimensional confinement of carriers in the InGaN islands that form the dots can reduce carrier migration to (and therefore recombination at) dislocations and other defects. In the present study, molecular beam epitaxial growth and the properties of InGaN/GaN self-assembled quantum dots have been investigated in detail. The quantum dots, emitting at 630nm, have been studied optically through temperature-dependent, excitation-dependent, and time-resolved photoluminescence. A radiative lifetime of ~2ns has been measured in these samples. Samples with varying number of dot layers were grown and characterized structurally by atomic force microscopy. The growth conditions of the dots have been optimized including the InGaN and GaN thickness and the nitrogen interruption time. The optimized dots have been incorporated into edge-emitting laser heterostructures. Other optimizations including the novel use of an all In0.18Al0.82N cladding are incorporated into the laser heterostructure to optimize the output power and reduce loss.The first red emitting quantum dot lasers, emitting at up to 630nm have been realized in the present study. These lasers show good performance compared with other material systems, including InGaAlP/GaAs and AlGaAs based red lasers.The maximum measured output power is 30mW, making them suitable for the applications discussed above.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120878/1/tfrost_1.pd

III-Nitride Self-assembled Nanowire Light Emitting Diodes and Lasers on (001) Silicon.

Substantial research is being devoted to the development of III-nitride light emitting diodes (LEDs) and lasers, which have numerous applications in solid state lighting. In particular, white LEDs play an increasingly important role in our daily lives. Current commercially available white LEDs are nearly all phosphor-converted, but these have some serious disadvantages. Planar quantum well (QW) devices on foreign substrates exhibit large threading dislocation densities, strong strain induced polarization field, and In-rich nanoclusters resulting in poor electron-hole wavefunction overlap, large emission peak shift with injection, and large efficiency drop at high injection currents in LEDs and large threshold current densities in lasers. The objective of this doctoral research is to investigate the prospects of self-assembled InGaN/GaN disks-in-nanowire (DNW) LEDs and lasers for solid state lighting. The research described here embodies a detailed study of the optical and structural characteristics of the nanowire heterostructures by varying the growth conditions and by surface passivation, and using the disks as the active region in high performance nanowire LEDs and gain medium in nanowire lasers on (001) silicon. Self-assembled InGaN/GaN DNWs are grown in a plasma-assisted molecular beam epitaxy (PA-MBE) system. Due to their large surface to volume ratio, the growth optimized and surface passivated DNWs on (001) silicon are relatively free of extended defects and have smaller polarization field resulting in higher radiative efficiencies. Blue-, green- and red-emitting DNW LEDs, with optimized nanowire densities, are demonstrated with reduced efficiency droop and smaller peak shift with injection. Phosphor-free white nanowire LEDs are realized by incorporating InGaN/GaN disks with different color emissions in the active region. The first ever monolithic edge-emitting electrically pumped green and red nanowire lasers on (001) silicon are demonstrated using DNWs as the gain media and are characterized by low threshold current densities of 1.76-2.88 kA/cm2, small peak shifts of 11-14.8 nm, large T0 of 234 K and large differential gain of 3x10-17 cm-2. Dynamic measurements performed on these lasers yield a maximum small signal modulation bandwidth of 5.8 GHz, extremely low value of chirp (0.8 Å) and a near-zero linewidth enhancement factor at the peak emission wavelength.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111490/1/shafat_1.pd

Design And Performance Of Laser Structures Based On Group III-Nitrides [QC689.55.S45 T363 2008 f rb].

Simulasi peranti bagi ciri elektrik, optik dan terma diod-diod laser (LDs) berasaskan GaN telah dikaji. Bagi laser-laser sedemikian adalah susah memperolehi lapisan penutup-p yang mempunyai ketebalan yang mencukupi, Device simulations for the electrical, optical and thermal characteristics of GaN-based laser diodes (LDs) have been investigated. It is difficult to obtain pcladding layers with sufficient thickness of high Al composition and high acceptor concentration

III-V Optoelectronic Devices: Room temperature CW operation of interband cascade laser & High efficiency p-side down InGaN/GaN solar cell

During the past two decades, the field of III-V optoelectronic devices has gained widespread interest as a result of advances in the performance and reliability of epitaxial structures. In principle, III-V materials can provide sources, detectors and optoelectronic components over wavelengths from UV to IR. During my Ph.D study, I have focused on two III-V optoelectronic devices: Mid-IR interband cascade lasers and group III-Nitride solar cells. In the first part of this dissertation, we will discuss development of a room temperature CW operation interband cascade laser and in the second part, we will discuss the concept of high efficiency III-N solar cells. Part I Lasers that emit in the mid-IR (3~5um) spectral region can be used in many civilian and military applications such as chemical sensing, free space optical communication and IR countermeasures. There are three types of lasers that can cover the Mid-IR region. First, conventional type-I quantum well (QW) lasers on GaSb substrates, second, inter-subband quantum cascade lasers (QCLs) on InP substrates and finally interband cascade laser with type-II alignment of the conduction and valence bands on GaSb substrates. Gallium Antimonide based type II interband cascade lasers (ICLs) cover the 3~4 um wavelength range, and it is the most natural match to the mid-IR. For most applications, it is required that the laser operates in continuous wave (CW) mode either at room temperature or at temperatures accessible to thermoelectric coolers. Recently, we have been able to operate interband cascade lasers in CW mode at room temperature with 62mW of output power, internal loss of 4.8cm-1, 170mW/A slope efficiency, and a threshold current density as low as 300 A/cm2 which are a significant milestone toward many applications. In the first part of this thesis, we are going to talk about the fundamental principles of operation of the ICLs and their applications. Secondly, we will present the development of a fabrication process. Third, we will discuss the performance characteristics of ICLs. Lasers were characterized by doing series of length dependent pulsed/CW measurements to obtain critical parameters at low temperature and at room temperature; such as wall plug efficiency, threshold current density, internal loss, and thermal impedance. For low temperature CW measurement, a specially designed vacuum chamber was used to prevent water condensation. Finally, we will present ICL optimization processes. For laser optimization, we re-designed the device structure, in particular the lower cladding region, the injection region, and the active region thickness, to achieve a higher confinement factor and lower loss, thus increasing the operating temperature and the output power. Part II Since the 1950s, silicon solar cells have been intensively studied and developed. Solar cell technology has greatly benefited from the maturity of silicon technology developed originally for the IC industry. This has led to the development of high quality single crystal silicon wafers with low dislocation densities. However, because of the poor spectral overlap between the absorption of silicon cells and the spectrum of solar light, silicon solar cells cannot fundamentally produce high efficiency solar cells. In order to achieve high efficiency solar cells, researchers have investigated many alternatives including tandem cells, GaAs, and III-Nitride materials. In the second part of this thesis, we will talk about the development of high efficiency III-Nitride solar cells using novel p-side InGaN/GaN materials, including device background, new solar cell design, fabrication process development, and preliminary device characterizations

Photonic platform and the impact of optical nonlinearity on communication devices

It is important to understand properties of different materials and the impact they have on devices used in communication networks. This paper is an overview of optical nonlinearities in Silicon and Gallium Nitride and how these nonlinearities can be used in the realization of optical ultra-fast devices targeting the next generation integrated optics. Research results related to optical lasing, optical switching, data modulation, optical signal amplification and photo-detection using Gallium Nitride devices based on waveguides are examined. Attention is also paid to hybrid and monolithic integration approaches towards the development of advanced photonic chips

Wide Bandgap Based Devices

Emerging wide bandgap (WBG) semiconductors hold the potential to advance the global industry in the same way that, more than 50 years ago, the invention of the silicon (Si) chip enabled the modern computer era. SiC- and GaN-based devices are starting to become more commercially available. Smaller, faster, and more efficient than their counterpart Si-based components, these WBG devices also offer greater expected reliability in tougher operating conditions. Furthermore, in this frame, a new class of microelectronic-grade semiconducting materials that have an even larger bandgap than the previously established wide bandgap semiconductors, such as GaN and SiC, have been created, and are thus referred to as “ultra-wide bandgap” materials. These materials, which include AlGaN, AlN, diamond, Ga2O3, and BN, offer theoretically superior properties, including a higher critical breakdown field, higher temperature operation, and potentially higher radiation tolerance. These attributes, in turn, make it possible to use revolutionary new devices for extreme environments, such as high-efficiency power transistors, because of the improved Baliga figure of merit, ultra-high voltage pulsed power switches, high-efficiency UV-LEDs, and electronics. This Special Issue aims to collect high quality research papers, short communications, and review articles that focus on wide bandgap device design, fabrication, and advanced characterization. The Special Issue will also publish selected papers from the 43rd Workshop on Compound Semiconductor Devices and Integrated Circuits, held in France (WOCSDICE 2019), which brings together scientists and engineers working in the area of III–V, and other compound semiconductor devices and integrated circuits