Center for Quantum Devices - Most Downloaded Journal Articles

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18.	High Power 3-12 μm Infrared Lasers: Recent Improvements and Future Trends M. Razeghi, S. Slivken, A. Tahraoui, A. Matlis, and Y.S. Park Advanced Research Workshop on Semiconductor Nanostructures, Queenstown, New Zealand; Proceedings -- February 5, 2003 ...[Visit Journal] In this paper, we discuss the progress of quantum cascade lasers (QCLs) grown by gas-source molecular beam epitaxy. Room temperature QCL operation has been reported for lasers emitting between 5-11 μm, with 9-11 μm lasers operating up to 425 K. Laser technology for the 3-5 μm range takes advantage of a strain-balanced active layer design. We also demonstrate record room temperature peak output powers at 9 and 11 μm (2.5 and 1 W, respectively) as well as record low 80K threshold current densities (250 A/cm²) for some laser designs. Preliminary distributed feedback (DFB) results are also presented and exhibit single mode operation for 9 μm lasers at room temperature. [reprint (PDF)]
18.	Passivation of type-II InAs/GaSb double heterostructure P.Y. Delaunay, A. Hood, B.M. Nguyen, D. Hoffman, Y. Wei, and M. Razeghi Applied Physics Letters, Vol. 91, No. 9, p. 091112-1-- August 27, 2007 ...[Visit Journal] Focal plane array fabrication requires a well passivated material that is resistant to aggressive processes. The authors report on the ability of type-II InAs/GaSb superlattice heterodiodes to be more resilient than homojunctions diodes in improving sidewall resistivity through the use of various passivation techniques. The heterostructure consisting of two wide band gap (5 µm) superlattice contacts and a low band gap active region (11 µm) exhibits an R₀A averaging of 13·Ω cm². The devices passivated with SiO₂, Na₂S and SiO₂ or polyimide did not degrade compared to the unpassivated sample and the resistivity of the sidewalls increased to 47 kΩ·cm. [reprint (PDF)]
18.	Reliability in room-temperature negative differential resistance characteristics of low-aluminum contact AlGaN/GaN double-barrier resonant tunneling diodes C. Bayram, Z. Vashaei, and M. Razeghi Applied Physics Letters, Vol. 97, No. 18, p. 181109-1-- November 1, 2010 ...[Visit Journal] AlGaN/GaN resonant tunneling diodes (RTDs), consisting of 20% (10%) aluminum-content in double-barrier (DB) active layer, were grown by metal-organic chemical vapor deposition on freestanding polar (c-plane) and nonpolar (m-plane) GaN substrates. RTDs were fabricated into 35-μm-diameter devices for electrical characterization. Lower aluminum content in the DB active layer and minimization of dislocations and polarization fields increased the reliability and reproducibility of room-temperature negative differential resistance (NDR). Polar RTDs showed decaying NDR behavior, whereas nonpolar ones did not significantly. Averaging over 50 measurements, nonpolar RTDs demonstrated a NDR of 67 Ω, a current-peak-to-valley ratio of 1.08, and an average oscillator output power of 0.52 mW. [reprint (PDF)]
18.	High Power 3-12 μm Infrared Lasers: Recent Improvements and Future Trends M. Razeghi, S. Slivken, A. Tahraoui, A. Matlis, and Y.S. Park Physica E: Low-Dimensional Systems and Nanostructures 11 (2-3)-- October 1, 2001 ...[Visit Journal] In this paper, we discuss the progress of quantum cascade lasers (QCLs) grown by gas-source molecular beam epitaxy. Room temperature QCL operation has been reported for lasers emitting between 5-11 μm, with 9-11 μm lasers operating up to 425 K. Laser technology for the 3-5 μm range takes advantage of a strain-balanced active layer design. We also demonstrate record room temperature peak output powers at 9 and 11 μm (2.5 and 1 W, respectively) as well as record low 80K threshold current densities (250 A/cm²) for some laser designs. Preliminary distributed feedback (DFB) results are also presented and exhibit single mode operation for 9 μm lasers at room temperature. [reprint (PDF)]
18.	AlGaN-based deep UV light emitting diodes with peak emission below 255 nm A. Yasan, R. McClintock, K. Mayes, P. Kung, and M. Razeghi SPIE Conference, Jose, CA, Vol. 5732, pp. 197-- January 22, 2005 ...[Visit Journal] We report on the growth and fabrication of AlGaN-based deep ultraviolet light-emitting diodes (LEDs) with peak emission of below 255 nm. In order to achieve such short wavelength UV LEDs, the Al mole fractions in the device layers should be greater than ~60%. This introdues serious challenges on the growth and doping of Al_xGa_1-xN epilayers. However, with the aid of a high-quality AlN template layer and refinement of the growth conditions we have been able to demonstrate UV LEDs emitting below 255 nm. [reprint (PDF)]
18.	UV photodetectors based on Al_xGa_1-xN grown by MOCVD A. Saxler, D. Walker, X. Zhang, P. Kung, J. Xu, and M. Razeghi SPIE Photonics West '96 Photodetectors: Materials and Devices; Proceedings 2685-- January 27, 1996 ...[Visit Journal] Metalorganic chemical vapor deposition was used to deposit Al_xGa_1-xN active layers with varying aluminum compositions on basal plane sapphire substrate. Al_xGa_1-xN (x < 0.5) ultraviolet photodetectors have been fabricated and characterized with cut-off wavelengths as short as 260 nm. Carrier lifetimes on the order of 10 milliseconds were estimated from frequency dependent measurements of the responsivity. [reprint (PDF)]
18.	GaInN/GaN Multi-Quantum Well Laser Diodes Grown by Low-Pressure Metalorganic Chemical Vapor Deposition P. Kung, A. Saxler, D. Walker, A. Rybaltowski, X. Zhang, J. Diaz, and M. Razeghi MRS Internet Journal of Nitride Semiconductor Research 3 (1)-- January 1, 1998 ...[Visit Journal] We report the growth, fabrication and characterization of GaInN/GaN multi-quantum well lasers grown on (00·1) sapphire substrates by low pressure metalorganic chemical vapor deposition. The threshold current density of a 1800 µm long cavity length laser was 1.4 kA/cm² with a threshold voltage of 25 V. These lasers exhibited series resistances of 13 and 14 Ω at 300 and 79 K, respectively. [reprint (PDF)]
18.	Low pressure metalorganic chemical vapor deposition of high quality AlN and GaN thin films on sapphire and silicon substrates P. Kung, X. Zhang, E. Bigan, and M. Razeghi Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995 ...[Visit Journal] High quality AlN and GaN epilayers have been grown on basal plane sapphire by low pressure metalorganic chemical vapor deposition. The X-ray rocking curve linewidth of the AlN and GaN films were about 100 and 30 arcsecs respectively. Sharp absorption edges were determined at 6.1 and 3.4 eV respectively. Successful donor-bound excitonic luminescence emissions were detected for GaN films grown on sapphire and silicon. Two additional lines at 3.37 and 3.31 eV were observed on GaN on sapphire and assumed to be impurity-related. Doping of GaN layers was achieved with magnesium. Mg-related photoluminescence emissions were successfully detected on as-grown samples, without any post-growth treatment. [reprint (PDF)]
18.	Band gap tunability of Type-II Antimonide-based superlattices M. Razeghi and B.M. Nguyen Physics Procedia, Vol. 3, Issue 2, p. 1207-1212 (14th International Conference on Narrow Gap Semiconductors and Systems NGSS-14, Sendai, Japan, July 13-17, 2009)-- January 31, 2010 ...[Visit Journal] Current state-of-the art infrared photon detectors based on bulk semiconductors such as InSb or HgCdTe are now relatively mature and have almost attained the theoretical limit of performance. It means, however, that the technology can not be expected to demonstrate revolutionary improvements, in terms of device performances. In contrasts, low dimensional quantum systems such as superlattices, quantum wells, quantum dots, are still the development stage, yet have shown comparable performance to the bulk detector family. Especially for the Type-II Antimony-based superlattices, recent years have seen significant improvements in material quality, structural design as well as fabrication techniques which lift the performance of Type-II superlattice photodetectors to a new level. In this talk, we will discuss the advantages of Type-II-superlattices, from the physical nature of the material to the practical realisms. We will demonstrate the flexibility in controlling the energy gap and their overall band alignment for the suppression of Auger recombination, as well as to create sophisticated hetero-designs. [reprint (PDF)]
18.	High-temperature high-power continuous-wave operation of buried heterostructure quantum-cascade lasers A. Evans, J.S. Yu, J. David, L. Doris, K. Mi, S. Slivken, and M. Razeghi Applied Physics Letters, 84 (3)-- January 19, 2004 ...[Visit Journal] We report cw operation of buried heterostructure quantum-cascade lasers (λ=6 µm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 333 K (60 °C). The high cw optical output powers of 446 mW at 293 K, 372 mW at 298 K, and 30 mW at 333 K are achieved with threshold current densities of 2.19, 2.35, and 4.29 kA/cm² respectively, for a high-reflectivity-coated, 9-µm-wide and 3-mm-long laser [reprint (PDF)]
18.	Aluminum nitride films on different orientations of sapphire and silicon K. Dovidenko, S. Oktyabrsky, J. Narayan, and M. Razeghi Journal of Applied Physics79 (5)-- March 1, 1996 ...[Visit Journal] The details of epitaxial growth and microstrictural characteristics of AlN films grown on sapphire (0001), (1012) and Si (100), (111) substrates were investigated using plan‐view and cross‐sectional high‐resolution transmission electron microscopy and x‐ray diffraction techniques. The films were grown by metalorganic chemical vapor deposition using TMA1+NH3+N2 gas mixtures. Different degrees of epitaxy were observed for the films grown on α‐Al₂O₃ and Si substrates in different orientations. The epitaxial relationship for (0001) sapphire was found to be (0001)AlN∥(0001)sap with in‐plane orientation relationship of [0110]AlN∥[1210]sap. This is equivalent to a 30° rotation in the basal (0001) plane. For (1012) sapphire substrates, the epitaxial relationship was determined to be (1120)AlN∥(1012)sap with the in‐plane alignment of [0001]AlN∥[1011]sap. The AlN films on (0001) α‐Al₂O₃ were found to contain inverted domain boundaries and a/3〈1120〉 threading dislocations with the estimated density of 10¹⁰ cm⁻². The density of planar defects (stacking faults) found in AlN films was considerably higher in the case of (1012) compared to (0001) substrates. Films on Si substrates were found to be highly textured c axis oriented when grown on (111) Si, and c axis textured with random in‐plane orientation on (100) Si. The role of thin‐film defects and interfaces on device fabrication is discussed. [reprint (PDF)]
18.	Harmonic injection locking of high-power mid-infrared quantum cascade lasers Feihu Wang, Steven Slivken, and Manijeh Razeghi OSA Photonics Research •https://doi.org/10.1364/PRJ.423573 ...[Visit Journal] High-power, high-speed quantum cascade lasers (QCLs) with stable emission in the mid-infrared regime are of great importance for applications in metrology, telecommunication, and fundamental tests of physics. Owing to the inter-sub-band transition, the unique ultrafast gain recovery time of the QCL with picosecond dynamics is expected to overcome the modulation limit of classical semiconductor lasers and bring a revolution for the next generation of ultrahigh-speed optical communication. Therefore, harmonic injection locking, offering the possibility to fast modulate and greatly stabilize the laser emission beyond the rate limited by cavity length, is inherently adapted to QCLs. In this work, we demonstrate for the first time the harmonic injection locking of a mid-infrared QCL with an output power over 1 watt in continuous-wave operation at 288 K. Compared with an unlocked laser, the inter-mode spacing fluctuation of an injection locked QCL can be considerably reduced by a factor above 1×10 E3, which permits the realization of an ultra-stable mid-infrared semiconductor laser with high phase coherence and frequency purity. Despite temperature change, this fluctuation can be still stabilized to hertz level by a microwave modulation up to ∼18 GHz. These results open up the prospect of the applications of mid-infrared QCL technology for frequency comb engineering, metrology and the next generation ultrahigh-speed telecommunication. It may also stimulate new schemes for exploring ultrafast mid-infrared pulse generation in QCLs. [reprint (PDF)]
18.	Current status of high performance quantum cascade lasers at the center for quantum devices M. Razeghi; A. Evans; Y. Bai; J. Nguyen; S. Slivken; S.R. Darvish; K. Mi Conference Proceedings - International Conference on Indium Phosphide and Related Materials. 588-593:[4266015] (2007)-- May 14, 2007 ...[Visit Journal] Mid-infrared laser sources are highly desired for laser-based trace chemical sensors, military countermeasures, free-space communications, as well as developing medical applications. While application development has been limited by the availability of adequate mid-infrared sources, InP-based quantum cascade lasers (QCLs) hold promise as inexpensive, miniature, portable solutions capable of producing high powers and operating at high temperatures with excellent beam quality and superior reliability. This paper discusses the most recent developments of application-ready high power (> 100 mW), continuous-wave (CW), mid-infrared QCLs operating above room temperature with lifetimes exceeding 13,000 hours. [reprint (PDF)]
18.	High Thermal Stability of κ-Ga2O3 Grown by MOCVD Junhee Lee, Honghyuk Kim, Lakshay Gautam and Manijeh Razeghi Lee, J.; Kim, H.; Gautam, L.; Razeghi, M. High Thermal Stability of κ-Ga2O3 Grown by MOCVD. Crystals 2021, 11, 446. https://doi.org/ 10.3390/cryst11040446 ...[Visit Journal] We report a high thermal stability of kappa gallium oxide grown on c-plane sapphire substrate by metal organic chemical vapor deposition. Kappa gallium oxide is widely known as a metastable polymorph transitioning its phase when subjected to a high temperature. Here, we show the kappa gallium oxide whose phase is stable in a high temperature annealing process at 1000 °C. These oxide films were grown at 690 °C under nitrogen carrier gas. The materials showed high electrical resistivity when doped with silicon, whereas the film conductivity was significantly improved when doped with both indium and silicon. This work provides a pathway to overcoming limitations for the advance in utilizing kappa gallium oxide possessing superior electrical characteristics. [reprint (PDF)]
18.	Sampled grating, distributed feedback quantum cascade lasers with broad tunability and continuous operation at room temperature S. Slivken, N. Bandyopadhyay, S. Tsao, S. Nida, Y. Bai, Q.Y. Lu and M. Razeghi Applied Physics Letters, Vol. 100, No. 26, p. 261112-1-- June 25, 2012 ...[Visit Journal] A dual-section, single-mode quantum cascade laser is demonstrated in continuous wave at room temperature with up to 114 nm (50 cm⁻¹) of tuning near a wavelength of 4.8 μm. Power above 100 mW is demonstrated, with a mean side mode suppression ratio of 24 dB. By changing the grating period, 270 nm (120 cm⁻¹) of gap-free electrical tuning for a single gain medium has been realized. [reprint (PDF)]
18.	Combined resonant tunneling and rate equation modeling of terahertz quantum cascade lasers Zhichao Chen , Andong Liu, Dong Chang , Sukhdeep Dhillon , Manijeh Razeghi , Feihu Wang Journal of Applied Physics, 135, 115703 ...[Visit Journal] Terahertz (THz) quantum cascade lasers (QCLs) are technologically important laser sources for the THz range but are complex to model. An efficient extended rate equation model is developed here by incorporating the resonant tunneling mechanism from the density matrix formalism, which permits to simulate THz QCLs with thick carrier injection barriers within the semi-classical formalism. A self-consistent solution is obtained by iteratively solving the Schrödinger-Poisson equation with this transport model. Carrier-light coupling is also included to simulate the current behavior arising from stimulated emission. As a quasi-ab initio model, intermediate parameters such as pure dephasing time and optical linewidth are dynamically calculated in the convergence process, and the only fitting parameters are the interface roughness correlation length and height. Good agreement has been achieved by comparing the simulation results of various designs with experiments, and other models such as density matrix Monte Carlo and non-equilibrium Green’s function method that, unlike here, require important computational resources. The accuracy, compatibility, and computational efficiency of our model enables many application scenarios, such as design optimization and quantitative insights into THz QCLs. Finally, the source code of the model is also provided in the supplementary material of this article for readers to repeat the results presented here, investigate and optimize new designs. [reprint (PDF)]
18.	Growth of “moth-eye” ZnO nanostructures on Si(111), c-Al2O3, ZnO and steel substrates by pulsed laser deposition Vinod E. Sandana, David J. Rogers, Ferechteh Hosseini Teherani, Philippe Bove, Michael Molinari, Michel Troyon, Alain Largeteau, Gérard Demazeau, Colin Scott, Gaelle Orsal, Henri-Jean Drouhin, Abdallah Ougazzaden, Manijeh Razeghi Phys. Status Solidi C., 1-5 (2013)-- August 6, 2013 ...[Visit Journal] Self-forming, vertically-aligned, arrays of black-body-like ZnO moth-eye nanostructures were grown on Si(111), c-Al₂O₃, ZnO and high manganese austenitic steel substrates using Pulsed Laser Deposition. X-ray diffraction (XRD) revealed the nanostructures to be well-crystallised wurtzite ZnO with strong preferential c-axis crystallographic orientation along the growth direction for all the substrates. Cathodoluminescence (CL) studies revealed emission characteristic of the ZnO near band edge for all substrates. Such moth-eye nanostructures have a graded effective refractive index and exhibit black-body characteristics. Coatings with these features may offer improvements in photovoltaic and LED performance. Moreover, since ZnO nanostructures can be grown readily on a wide range of substrates it is suggested that such an approach could facilitate growth of GaN-based devices on mismatched and/or technologically important substrates, which may have been inaccessible till present. [reprint (PDF)]
18.	Ultraviolet Detectors for AstroPhysics Present and Future M. Ulmer, M. Razeghi, and E. Bigan Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 239-- February 6, 1995 ...[Visit Journal] Astronomical instruments for the study of UV astronomy have been developed for NASA missions such as the Hubble Space Telescope. The systems that are `blind to the visible' (`solar-blind') yet sensitive to the UV that have been flown in satellites have detective efficiencies of about 10 to 20%, although typically electron bombardment charge coupled devices are higher at 30 - 40% and ordinary CCDs achieve 1 - 5%. Therefore, there is a large payoff still to be gained by further improvements in the performance of solar blind UV detectors. We provide a brief review of some aspects of UV astronomy, UV detector development, and possible technologies for the future. We suggest that a particularly promising future technology is one based on the ability of investigators to produce high quality films made of wide bandgap III-V semiconductors. [reprint (PDF)]
18.	Electrically pumped photonic crystal distributed feedback quantum cascade lasers Y. Bai, S.R. Darvish, S. Slivken, P. Sung, J. Nguyen, A. Evans, W. Zhang, and M. Razeghi Applied Physics Letters, Vol. 91, No. 14, p. 141123-1-- October 1, 2007 ...[Visit Journal] We demonstrate electrically pumped, room temperature, single mode operation of photonic crystal distributed feedback (PCDFB) quantum cascade lasers emitting at ~4.75 µm. Ridge waveguides of 100 µm width were fabricated with both PCDFB and Fabry-Pérot feedback mechanisms. The Fabry-Pérot device has a broad emitting spectrum and a double lobed far-field character. The PCDFB device, as expected, has primarily a single spectral mode and a diffraction limited far field characteristic with a full angular width at half maximum of 2.4°. This accomplishment represents the first step in power scaling of single mode, midinfrared laser diodes operating at room temperature. [reprint (PDF)]
18.	Intersubband hole absorption in GaAs-GaInP Quantum Wells grown by Gas Source Molecular Beam Epitaxy J. Hoff, C. Jelen, S. Slivken, E. Michel, O. Duchemin, E. Bigan, and M. Razeghi with G. Brown and S.M. Hegde (Wright Laboratory) Applied Physics Letters 65 (9)-- August 29, 1994 ...[Visit Journal] P-doped GaAs‐GaInP quantum wells have been grown on GaAs substrate by gas source molecular beam epitaxy. Structural quality has been evidenced by x-ray diffraction. A narrow low-temperature photoluminescence full width at half‐maximum has been measured. Strong hole intersubband absorption has been observed at 9 μm, and its dependence on light polarization has been investigated. [reprint (PDF)]
18.	Photoconductance measurements on InTlSb/InSb/GaAs grown by low-pressure metalorganic chemical vapor deposition P.T. Staveteig, Y.H. Choi, G. Labeyrie, E. Bigan, and M. Razeghi Applied Physics Letters 64 (4)-- January 24, 1994 ...[Visit Journal] We report infrared photoconductors based on InTlSb/InSb grown by low‐pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The photoresponse spectrum extends up to 8 μm at 77 K. The absolute magnitude of the photoresponse is measured as a function of bias. The specific detectivity is estimated to be 3×10⁸ Hz^½·cm·W^-1 at 7 μm wavelength. [reprint (PDF)]
18.	Evaluating the size-dependent quantum efficiency loss in a SiO₂-Y₂O₃hybrid gated type-II InAs/GaSb long-infrared photodetector array G. Chen , A. M. Hoang , and M. Razeghi Applied Physics Letters 104 , 103509 (2014)-- March 14, 2014 ...[Visit Journal] Growing Y₂O₃ on 20 nm SiO₂ to passivate a 11 μm 50% cut-off wavelength long-wavelength infrared type-II superlattice gated photodetector array reduces its saturated gate bias (VG_sat ) to −7 V. Size-dependent quantum efficiency (QE) losses are evaluated from 400 μm to 57 μm size gated photodiode. Evolution of QE of the 57 μm gated photodiode with gate bias and diode operation bias reveals different surface recombination mechanisms. At 77 K and VG,sat , the 57 μm gated photodiode exhibits QE enhancement from 53% to 63%, and it has 1.2 × 10⁻⁵ A/cm² dark current density at −200 mV, and a specific detectivity of 2.3 × 10¹² Jones. [reprint (PDF)]
18.	High-power laser diodes based on InGaAsP alloys M. Razeghi Nature, Vol.369, p.631-633-- June 23, 1994 ...[Visit Journal] HIGH-POWER, high-coherence solid-state lasers, based on dielectric materials such as ruby or Nd:YAG (yttrium aluminium garnet), have many civilian and military applications. The active media in these lasers are insulating, and must therefore be excited (or ‘pumped’) by optical, rather than electrical, means. Conventional gas-discharge lamps can be used as the pumping source, but semiconductor diode lasers are more efficient, as their wavelength can be tailored to match the absorption properties of the lasing material. Semiconducting AlGaAs alloys are widely used for this purpose, but oxidation of the aluminium and the spreading of defects during device operation limit the lifetime of the diodes3, and hence the reliability of the system as a whole. Aluminium-free InGaAsP compounds, on the other hand, do not have these lifetime-limiting properties. We report here the fabrication of high-power lasers based on InGaAsP (lattice-matched to GaAs substrates), which operate over the same wavelength range as conventional AlGaAs laser diodes and show significantly improved reliability. The other optical and electrical properties of these diodes are either comparable or superior to those of the AlGaAs system. [reprint (PDF)]
18.	Growth of GaInAs‐InP multiquantum wells on garnet (GGG=Gd3Ga5O12) substrate by metalorganic chemical vapor deposition M. Razeghi; P‐L. Meunier; P. Maurel M. Razeghi, P‐L. Meunier, P. Maurel; Growth of GaInAs‐InP multiquantum wells on garnet (GGG=Gd3Ga5O12) substrate by metalorganic chemical vapor deposition. J. Appl. Phys. 15 March 1986; 59 (6): 2261–2263-- March 15, 1986 ...[Visit Journal] Ga0.47In0.53As‐InP multiquantum wells grown by low‐pressure metalorganic chemical vapor deposition on garnet (GGG=Gd3Ga5O12 with a=12.383 Å) substrates are presented for the first time. The x‐ray diffraction pattern shows that the orientation of the epitaxial layer is (111) while the underlying substrate orientation is (100). The photoluminescence at 77 K is due to the GaInAs layers. [reprint (PDF)]
18.	AlGaN/AlN MOVPE heteroepitaxy: pulsed co-doping SiH4 and TMIn Ilkay Demir, Yusuf Koçak, A. Emre Kasapoğlu, Manijeh Razeghi, Emre Gür and Sezai Elagoz Semicond. Sci. Technol. 34 075028-- June 24, 2019 ...[Visit Journal] We report a new growth approach pulsed co-doping growth of Al_xGa_1−xN (x > 0.5) epilayers on AlN/Al₂O₃ templates by metal organic vapor phase epitaxy (MOVPE). Using this approach SiH₄ (silane) and TMIn (trimethylindium) supplied to the growth chamber alternately and pulsed during the growth of AlGaN epilayers. Structural and morphological quality of AlGaN epilayers were investigated by high resolution x-ray diffraction (HR-XRD), atomic force microscopy (AFM), Raman spectroscopy, and scanning electron microscopy (SEM) techniques. It has shown that higher crystalline quality with low full width at half maximum (FWHM) and smoother surface morphology with reduced hexagonal hillock density has been obtained by the pulsed co-doping growth approach. Volcano like hillock structures has been confirmed by Raman mapping. [reprint (PDF)]

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