High reflectivity and broad bandwidth AlN/GaN distributed Bragg reflectors grown by molecular-beam epitaxy (original) (raw)
Related papers
High reflectance III-nitride Bragg reflectors grown by molecular beam epitaxy
2000
A 20.5 period distributed Bragg reflector stack based on AlN/GaN has been grown on ͑0001͒ sapphire by electron cyclotron resonance plasma-assisted molecular-beam epitaxy. Peak reflectance up to 95% was observed at a wavelength of 392.5 nm. Cross-section transmission electron microscopy studies indicate that the interface of GaN-on-AlN is always sharper and more distinct than the interface of AlN-on-GaN. This is attributed to the different growth modes of AlN and GaN. When AlN grows on GaN, it tends to grow in a two-dimensional mode ͑Frank-van der Merwe mode͒ whereas GaN grows on AlN in a three-dimensional mode ͑Stranski-Krastanov mode͒. Based on these findings, the experimental reflectance data were simulated using the transmission matrix method.
Journal of Crystal Growth, 2009
A high-quality AlN/GaN distributed Bragg-reflectors (DBR) was successfully grown on sapphire substrate by low-pressure metal-organic chemical vapor deposition using ultra-thin AlN/GaN superlattice insertion layers (SLILs). The reflectivity of AlN/GaN DBR with ultra-thin AlN/GaN SLIL was measured and achieved blue peak reflectivity of 99.4% at 462 nm. The effect of ultra-thin AlN/GaN superlattice insertion layer was examined in detail by transmission electron microscopy, and indicated that the crack of AlN/GaN DBR can be suppress by inserting AlN/GaN SLIL. For electronic properties, the turn on voltage is about 4.1 V and CW laser action of vertical-cavity surface-emitting laser (VCSEL) was achieved at a threshold injection current of 1.4 mA at 77 K, with an emission wavelength of 462 nm.
GaN-based vertical cavities on highly reflective and crack-free nitride distributed Bragg reflectors
Gallium Nitride Materials and Devices IV, 2009
We report on GaN-based vertical cavities on highly reflective and crack-free 40.5 pair of AlGaN/GaN distributed Bragg reflectors (DBRs) by using a selective growth method to avoid wafer cracking that is commonly observed in conventional planar Al(Ga)N/GaN DBRs. An Al 0.46 Ga 0.54 N/GaN DBR with ~ 98% reflectivity was selectively grown with square patterns of up to 150 × 150 μm 2 in size, which were separated from each other by 10 μm wide SiO 2 mask stripes. Vertical cavity structures employing InGaN/InGaN multiple quantum wells (MQWs) were grown on these crackfree patterned DBRs and capped with 13 pair SiO 2 /SiN x DBRs to complete the full cavity structure. A cavity mode at ~ 442 nm in 150 × 150 μm 2 area was observed, having a quality factor of ~300. The selective growth technique to eliminate crack formation is very promising for the fabrication of nitride-based vertical-cavity surface emitting laser devices.
Distributed Bragg reflectors based on AlN/GaN multilayers
Applied Physics Letters, 1999
A 20.5 period distributed Bragg reflector stack based on AlN/GaN has been grown on ͑0001͒ sapphire by electron cyclotron resonance plasma-assisted molecular-beam epitaxy. Peak reflectance up to 95% was observed at a wavelength of 392.5 nm. Cross-section transmission electron microscopy studies indicate that the interface of GaN-on-AlN is always sharper and more distinct than the interface of AlN-on-GaN. This is attributed to the different growth modes of AlN and GaN. When AlN grows on GaN, it tends to grow in a two-dimensional mode ͑Frank-van der Merwe mode͒ whereas GaN grows on AlN in a three-dimensional mode ͑Stranski-Krastanov mode͒. Based on these findings, the experimental reflectance data were simulated using the transmission matrix method.
Group-III nitride VCSEL structures grown by molecular beam epitaxy
2000
III-nitride VCSEL structures designed for electron-beam pumping have been grown by molecular beam epitaxy (MBE). The structures consist of a sapphire substrate on which an AlN/GaN distributed Bragg reflector (DBR) with peak reflectance >99% at 402 nm is deposited. The active region consists of a 2-(lambda) cavity with 25 In0.1Ga0.9N/GaN multiquantum wells (MQWs) whose emission coincides with the high reflectance region of the DBR. The thicknesses of the InGaN wells and the GaN barriers are 35 angstrom and 75 angstrom respectively. The top reflector consists of a silver metallic mirror which prevents charging effects during electron-beam pumping. The structure was pumped from the top- side with a cw electron-beam using a modified cathodoluminescence (CL) system mounted on a scanning electron microscope chamber. Light output was collected from the polished sapphire substrate side. Measurements performed at 100 K showed intense emission at 407 nm with narrowing of the linewidth with increasing beam current. A narrow emission linewidth of 0.7 nm was observed indicating the onset of stimulated emission.
Japanese Journal of Applied Physics, 2006
In this paper, we report a GaN-based microcavity light-emitting diode (MCLED) which is composed of 25 pairs of highreflectivity GaN/AlN distributed Bragg reflector (DBR) and 6 pairs of ex-situ deposited SiO 2 /TiO 2 dielectric mirrors. The electroluminescence peak of this structure matched well with the high reflectance area of the top and bottom DBRs, and shows a narrow emission of approximately 6.7 nm. The fabricated device also shows a more excellent performance on the stability of the emission peak wavelength while varying injection current density and operating temperature than a regular LED.
Applied Physics Letters, 2016
We report the crack-free growth of a 45-pair Al 0.30 Ga 0.70 N/Al 0.04 Ga 0.96 N distributed Bragg reflector (DBR) on 2 in. diameter AlN/sapphire template by metalorganic chemical vapor deposition. To mitigate the cracking issue originating from the tensile strain of Al 0.30 Ga 0.70 N on GaN, an AlN template was employed in this work. On the other hand, strong compressive strain experienced by Al 0.04 Ga 0.96 N favors 3D island growth, which is undesired. We found that inserting an 11 nm thick GaN interlayer upon the completion of AlN template layer properly managed the strain such that the Al 0.30 Ga 0.70 N/Al 0.04 Ga 0.96 N DBR was able to be grown with an atomically smooth surface morphology. Smooth surfaces and sharp interfaces were observed throughout the structure using high-angle annular dark-field imaging in the STEM. The 45-pair AlGaN-based DBR provided a peak reflectivity of 95.4% at k ¼ 368 nm with a bandwidth of 15 nm.
physica status solidi (c), 2004
Series of ten-, twenty-, and thirty-period (Al,Ga)N-based distributed Bragg reflectors (DBR) have been grown by low-pressure metalorganic vapour phase epitaxy on bulk GaN substrates. Respective mirror target wavelength reflectances of 54, 72, and 86%, as well as stop band-widths lie in nearly exact agreement with the simulations. The DBR are found to be crack-free if pseudomorphically grown on partially relaxed (Ga,In)N compliance layers. In a second series GaN lambda-cavities are introduced into the mirror structures forming nominally symmetric Fabry-Perot resonators sandwiched either between the air/GaNinterface and an underlying Al x Ga 1-x N/GaN-Bragg mirror, or sandwiched between a top-and a bottom-DBR with various numbers of Al x Ga 1-x N/GaN quarter-wave layers. Measured reflectance spectra of samples without top-DBR agree well with the simulations, whereas reflectance spectra of samples with top-DBR remain significantly below the simulations. Upon introduction of Al x Ga 1-x N/GaN-based bottom-DBR with 90% target wavelength reflectance up to 15.5% light extraction are predicted for encapsulated light emitting diodes.
Group-III nitride VCSEL structures grown by molecular beam epitaxy
Physics and Simulation of Optoelectronic Devices VIII, 2000
111-nitride VCSEL structures designed for electron-beam pumping have been grown by molecular beam epitaxy (MBE). The structures consist of a sapphire substrate on which an A1N/GaN distributed Bragg reflector (DBR) with peak reflectance >99% at 402nm is deposited. The active region consists of a 2-2 cavity with 25 In01Ga9N/GaN multiquantum wells (MQWs) whose emission coincides with the high reflectance region of the DBR. The thicknesses of the InGaN wells and the GaN barriers are 35A and 75A respectively. The top reflector consists of a silver metallic mirror which prevents charging effects during electron-beam pumping. The structure was pumped from the top-side with a cw electron-beam using a modified cathodoluminescence (CL) system mounted on a scanning electron microscope chamber. Light output was collected from the polished sapphire substrate side. Measurements performed at lOOK showed intense emission at 407nm with narrowing of the linewidth with increasing beam current. A narrow emission linewidth of O.7nm was observed indicating the onset of stimulated emission.