Spatially resolved optical emission of cubic GaN/AlN multi-quantum well structures

2014 ◽  
Vol 1736 ◽  
Author(s):  
D.J. As ◽  
R. Kemper ◽  
C. Mietze ◽  
T. Wecker ◽  
J.K.N. Lindner ◽  
...  
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Film Thickness ◽  
Quantum Wells ◽  
Emission Intensity ◽  
Optical Emission ◽  
Quantum Well Structures ◽  
Spatially Resolved ◽  
Scanning Transmission ◽  
Cubic Gan

ABSTRACTIn this contribution we report on the optical properties of cubic AlN/GaN asymmetric multi quantum wells (MQW) structures on 3C-SiC/Si (001) substrates grown by radio-frequency plasma-assisted molecular beam epitaxy (MBE). Scanning transmission electron microscopy (STEM) and spatially resolved cathodoluminescence (CL) at room temperature and at low temperature are used to characterize the optical properties of the cubic AlN/GaN MQW structures. An increasing CL emission intensity with increasing film thickness due to the improved crystal quality was observed. This correlation can be directly connected to the reduction of the linewidth of x-ray rocking curves with increasing film thickness of the c-GaN films. Defects like stacking faults (SFs) on the {111} planes, which also can be considered as hexagonal inclusions in the cubic crystal matrix, lead to a decrease of the CL emission intensity. With low temperature CL line scans also monolayer fluctuations of the QWs have been detected and the observed transition energies agree well with solutions calculated using a one-dimensional (1D) Schrödinger-Poisson simulator.

Structural and Optical Properties of InGaN/GaN Multi-Quantum Well Structures with Different Well Widths

2002 ◽  
Vol 722 ◽  
Author(s):  
Young-Hoon KIM ◽  
Chang-Soo KIM ◽  
Sam-Kyu NOH ◽  
Jae-Young LEEM ◽  
Kee-Young LIM ◽  
...  
Keyword(s):  
Optical Properties ◽  
Quantum Wells ◽  
Emission Intensity ◽  
Lattice Relaxation ◽  
Multiple Quantum ◽  
X Ray Diffraction ◽  
Reciprocal Space Mapping ◽  
Quantum Well Structures ◽  
X Ray ◽  
Multi Quantum Well

AbstractThe structural and the optical properties of 10-period In0.15Ga0.85N/GaN multiple quantum wells (MQWs) have been investigated using HRXRD (high-resolution X-ray diffraction) and PL (photoluminescence). For the samples, the barrier thickness was kept constant, 7.5 nm and the well thicknesses were varied, 1.5, 3.0, 4.5, and 6.0 nm. For the structural characterization, an ω/2θ-scan and an ω-scan for GaN (00 2) reflection and a reciprocal space mapping (RSM) around the GaN (10 5) lattice point were employed. The average strain for the MQWs increased as the well thickness increased. The MQW with a 6.0 nm well thickness experienced lattice relaxation and the crystallinity of the sample was poor compared to that of the other samples. MQWs with well thicknesses of 1.5, 3.0 and 4.5 nm, however, maintained lattice coherency with the GaN epilayers underneath, and the critical well thickness for lattice relaxation of the MQWs used in the study was 6.0 nm. The PL spectra showed that the relative emission intensity of the sample with a 6.0 nm well thickness was lower than for the others, a fact consistent with the X-ray results. The emission intensity, therefore, is considered to be affected by defects due to lattice relaxation of the epilayer.

Optical properties of quantum wells grown upon gas source molecular‐beam epitaxy low‐temperature buffers

1991 ◽  
Vol 69 (11) ◽  
pp. 7942-7944 ◽  
Author(s):  
K. T. Shiralagi ◽  
R. A. Puechner ◽  
K. Y. Choi ◽  
R. Droopad ◽  
G. N. Maracas
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Low Temperature ◽  
Quantum Wells ◽  
Molecular Beam ◽  
Gas Source

scholarly journals Radiative Lifetime of Excitons in GaInN/GaN Quantum Wells

1996 ◽  
Vol 1 ◽  
Author(s):  
Jin Seo Im ◽  
Volker Härle ◽  
Ferdinand Scholz ◽  
Andreas Hangleiter
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Decay Time ◽  
Elevated Temperatures ◽  
Radiative Lifetime ◽  
Thermal Dissociation ◽  
Interface Roughness ◽  
Nonradiative Recombination ◽  
Quantum Well Structures ◽  
Decay Times

We have studied GaInN/GaN quantum well structures grown by LP-MOVPE by picosecond time-resolved photoluminescence spectroscopy. For the quantum wells we find rather long PL decay times of up to 600 ps at low temperature. At temperatures higher than about 100 K, the decay time decreases rapidly, reaching about 75 ps at room temperature. From measurements of the integrated PL intensity, we conclude that this decrease of the decay time is due to nonradiative recombination processes. By combining our data for the lifetime and the intensity, we derive the radiative lifetime, which is constant at low temperature and increases at elevated temperatures. We explain this behavior on the basis of the interface roughness at low temperature and thermal dissociation of excitons at higher temperatures.

scholarly journals Optical Properties of AlGaN Quantum Well Structures

2000 ◽  
Vol 5 (S1) ◽  
pp. 696-702 ◽  
Author(s):  
Hideki Hirayama ◽  
Yasushi Enomoto ◽  
Atsuhiro Kinoshita ◽  
Akira Hirata ◽  
Yoshinobu Aoyagi
Keyword(s):  
Optical Properties ◽  
Quantum Wells ◽  
Wide Bandgap ◽  
Near Band Edge ◽  
Quantum Well Structures ◽  
Al Content ◽  
Organic Vapor ◽  
Metal Organic ◽  
Pl Emission ◽  
High Al Content

We demonstrate 230-250 nm efficient ultraviolet (UV) photoluminescence (PL) from AlN(AlGaN)/AlGaN multi-quantum-wells (MQWs) fabricated by metal-organic vapor-phase-epitaxy (MOVPE). Firstly, we show the PL properties of high Al content AlGaN bulk (Al content: 85-95%) emitting from near band-edge. We systematically investigated the PL properties of AlGaN-MQWs consisting of wide bandgap AlGaN (Al content: 53-100%) barrier. We obtained efficient PL emission of 234 and 245 nm from AlN/Al0.18Ga0.82N and Al0.8Ga0.2N/Al0.18Ga0.82N MQWs, respectively, at 77 K. The optimum value of well thickness was approximately 1.5 nm. The emission from the AlGaN MQWs were several tens of times stronger than that of bulk AlGaN. We found that the most efficient PL is obtained at around 240 nm from AlGaN MQWs with Al0.8Ga0.2N barriers. Also, we found that the PL from AlGaN MQW is as efficient as that of InGaN QWs at 77 K.

OPTICAL PROPERTIES OF CdTe/ZnTe ULTRATHIN QUANTUM WELLS GROWN BY ATOMIC LAYER EPITAXY

2002 ◽  
Vol 09 (05n06) ◽  
pp. 1667-1670 ◽  
Author(s):  
M. GARCÍA-ROCHA ◽  
I. HERNÁNDEZ-CALDERÓN
Keyword(s):  
Optical Properties ◽  
Low Temperature ◽  
Quantum Wells ◽  
Gaas Substrate ◽  
Room Temperature ◽  
Diffusion Length ◽  
Substrate Surface ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Low Temperature Photoluminescence

Ultrathin quantum wells (UTQWs) of CdTe within ZnTe barriers were successfully grown by atomic layer epitaxy (ALE) on GaAs(001) substrates. ALE growth of CdTe was performed by alternate exposure of the substrate surface to individual fluxes of Cd and Te. Two different samples with 2-monolayer (ML) (substrate temperature Ts= 270° C ) and 4 ML (Ts = 290° C ) CdTe QWs were grown. Low temperature photoluminescence (PL) experiments exhibited intense and sharp peaks associated to the 2 ML QWs at 2.26 eV. In the case of the nominally 4-ML-thick QW the PL spectrum presented an intense peak around 2.13 eV and two weak features around 2.04 and 1.91 eV. The first peak is attributed to ~ 3 ML QW and the second one to ~ 4 ML QW. The dominance of the 3 ML peak is mainly attributed to Cd loss in the QW due to its substitution by Zn atoms. Due to a high diffusion length of the photogenerated carriers in the barriers, quite weak signals from the ZnTe barriers were observed in both cases. Room temperature (RT) photoreflectance (PR) spectra showed contributions from the CdTe UTQWs, the ZnTe barriers, and the GaAs substrate.

STEM-CL investigations on the influence of stacking faults on the optical emission of cubic GaN epilayers and cubic GaN/AlN multi-quantum wells

2015 ◽  
Vol 12 (4-5) ◽  
pp. 469-472 ◽  
Author(s):  
R. M. Kemper ◽  
P. Veit ◽  
C. Mietze ◽  
A. Dempewolf ◽  
T. Wecker ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Stacking Faults ◽  
Optical Emission ◽  
Cubic Gan

Structural and Optical Properties of InGaN/GaN Multi-Quantum Well Structures with Different Indium Compositions

2003 ◽  
Vol 764 ◽  
Author(s):  
Chang-Soo Kim ◽  
Sam-Kyu Noh ◽  
Kyuhan Lee ◽  
Sunwoon Kim ◽  
Jay P. Song
Keyword(s):  
Optical Properties ◽  
Quantum Wells ◽  
Lattice Relaxation ◽  
Multiple Quantum ◽  
Structural And Optical Properties ◽  
Rich Region ◽  
Quantum Well Structures ◽  
Peak Intensity ◽  
Peak Energy ◽  
Multi Quantum Well

AbstractThe structural and optical properties of InGaN/GaN multiple quantum wells (MQWs) grown on sapphire by MOCVD have been investigated using high-resolution XRD, PL and TEM. The samples consisted of 10 periods of InGaN wells with 6.5nm thickness. The designed indium compositions were 15, 20, 25 and 30% (samples C15, C20, C25, C30, respectively). The thickness of GaN barrier was 7.5nm. The MQW in sample C15 maintained lattice coherency with the GaN epilayer underneath, the MQWs in the other samples, however, experienced lattice relaxation. The crystallinity of the samples decreased considerably with In concentration. As In composition increased, PL peak energy showed a red-shift, and the FWHM of the peaks increased. The increase in the FWHM is attributed to the defects due to the lattice relaxation. For C25 the PL peak intensity increased sharply in spite of the defects due to the lattice relaxation of the sample. It is concluded that the results are related to the In-rich region due to indium phase separation which was observed by TEM image.

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