Density Of Quantum Dots Research Articles

Single quantum dot selection and tailor-made photonic device integration using nanoscale focus pinspot.

Among the diverse platforms of quantum light sources, epitaxially grown semiconductor quantum dots (QDs) are one of the most attractive workhorses for realizing quantum photonic technologies owing to their outstanding brightness and scalability. However, the spatial and spectral randomness of most QDs severely hinders the construction of large-scale photonic platforms. In this work, we present a methodology to deterministically integrate single QDs with tailor-made photonic structures. We apply a nondestructive luminescence picking method termed as nanoscale focus pinspot (NFP) using helium ion microscopy to reduce the luminous QD density while retaining the surrounding medium. We extract only a single QD emission out of the high-density ensemble QDs. Then the tailor-made photonic structure of a circular Bragg reflectors (CBR) are designed and deterministically integrated with the selected QD. Given that the microscopy can image with nanoscale resolution and apply NFP in situ, photonic devices can be deterministically fabricated on target QDs. The extraction efficiency of the NFP-selected QD emission is improved by 25 times after the CBR integration. Since the NFP method only controls the luminescence without destroying the medium, it is applicable to various photonic structures such as photonic waveguides or photonic crystal cavities regardless of materials. This article is protected by copyright. All rights reserved.

Near infrared photoluminescence of Si1–xGex quantum dots fabricated by double hot Ge+/Si+ implantation into SiO2 layer

In this study, we developed very simple and ULSI (ultra large scale integration) compatible fabrication processes for group-IV (Si1–xGex and Si) semiconductor quantum dots (QDs) to apply hybrid ULSIs with photonic and electron devices, using double Ge+/Si+ hot-ion implantation into a SiO2 layer with larger bandgap EG and the post-furnace annealing. We successfully demonstrated the near-infrared (IR) photoluminescence (PL) from Si1–xGex-QDs. Transmission electron microscopy observations of single-crystallized Si1–xGex-QDs revealed that the diameter and the QD density were 3.6 ± 0.9 nm and (2.6 ± 0.4) × 1012 cm−2, respectively. In addition, Ge atoms were detected in the Si1–xGex-QDs by the energy dispersive x-ray spectroscopy analysis, and the Ge fraction of Si1–xGex-QDs was varied from 0.06 to 0.26 by changing the Ge ion dose. The increase in the PL intensity by forming gas annealing was attributed to the dangling-bond reduction by the H-atom termination method. The PL spectrum of Si1–xGex-QDs was fitted by PL components of two QD structures containing Si1–xGex and Si materials. The PL intensity and PL-peak photon energy of Si1–xGex-QDs strongly depended on the Ge fraction. The Si1–xGex-QDs achieved the maximum PL intensity at x ≈ 0.13. High PL-peak photon energy (∼1.31 eV) of Si1–xGex-QDs is attributed to the quantum confinement effect of carriers in QDs. Consequently, group-IV semiconductor QDs including Si1–xGex, Si, SiC, and C, through the simple hot-ion implantation into the SiO2 layer, exhibited a wide range of PL emissions from the near-IR to ultraviolet regions.

InAs quantum emitters at telecommunication wavelengths grown by droplet epitaxy

InAs quantum dots at telecommunication wavelengths are desired as single-photon sources, but a growth technique that enables wide control over quantum dot size, density, and morphology is needed. Droplet epitaxy is well suited for this purpose, but InAs nanostructures tend to form as rings on (001) InGaAs, InAlAs, and InP surfaces. In this work, we investigate how surface diffusion can be manipulated to grow quantum dots by molecular beam epitaxy without using high-index substrates or metamorphic buffers. First, surface diffusion characteristics of In on In0.52Al0.48As are compared to In and Ga on In0.53Ga0.47As. Then, a two-step arsenic exposure protocol is applied to modify the droplet crystallization step, resulting in a series of different nanostructure morphologies that have narrow-linewidth emission between 1200 and 1520 nm at 4 K. Ultimately, we show that controlling surface diffusion of the group-III species during growth is critical for achieving quantum dots appropriate for single-photon sources at telecommunication wavelengths.

J–V characteristics of dark current in truncated conical quantum dot infrared photodetectors (QDIPs)

Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photodetection due to its controllable heterojunction bandgap and sensitivity to normal incident radiation. It is expected to be superior to infrared photodetectors of mature technologies such as Mercury Cadmium Telluride (HgCdTe) or a quantum well infrared photodetector. In the presented paper, we have developed a theoretical model for the dark current in truncated conical QDIP as the truncated conical shaped QD structure is more appropriate to describe the fabricated dots. The dark current model is based on the drift diffusion model solving the main governing Poisson’s and continuity equations. In this model, the carrier mobility is calculated by solving time-dependent Boltzmann transport equation in the photodetector material with embedded truncated conical QDs using finite difference technique. The results of the developed model have been compared with the dark current characteristics with published experimental results of Indium Arsenide/Gallium Arsenide (InAs/GaAs) truncated QDIP. The effects of QD volume, QD aspect ratio and QD density and the operating temperature on the dark current characteristics have also been investigated.

Anisotropic Etching of InGaN Thin Films with Photoelectrochemical Etching to Form Quantum Dots

Traditional methods for synthesizing InGaN quantum dots (QDs), such as the Stranski-Krastanov growth, often result in QD ensembles with low density and non-uniform size distribution. To overcome these challenges, forming QDs using photoelectrochemical (PEC) etching with coherent light has been developed. Anisotropic etching of InGaN thin films is demonstrated here with PEC etching. InGaN films are etched in dilute H2SO4 and exposed to a pulsed 445 nm laser with a 100 mW/cm2 average power density. Two potentials (0.4 V or 0.9 V) measured with respect to an AgCl|Ag reference electrode are applied during PEC etching, resulting in different QDs. Atomic force microscope images show that while the QD density and sizes are similar for both applied potentials, the heights are more uniform and match the initial InGaN thickness at the lower applied potential. Schrodinger-Poisson simulations show that polarization-induced fields in the thin InGaN layer prevent positively charged carriers (holes) from arriving at the c-plane surface. These fields are mitigated in the less polar planes resulting in high etch selectivity for the different planes. The higher applied potential overcomes the polarization fields and breaks the anisotropic etching.

Optical Gain of Vertically Coupled Cd0.6Zn0.4Te/ZnTe Quantum Dots.

The optical modal gain of Cd0.6Zn0.4Te/ZnTe double quantum dots was measured using a variable stripe length method, where large and small quantum dots are separated with a ZnTe layer. With a large (~18 nm) separation layer thickness of ZnTe, two gain spectra were observed, which correspond to the confined exciton levels of the large and small quantum dots, respectively. With a small (~6 nm) separation layer thickness of ZnTe, a merged single gain spectrum was observed. This can be attributed to a coupled state between large and small quantum dots. Because the density of large quantum dots (4 × 1010 cm-2) is twice the density of small quantum dots (2 × 1010 cm-2), the density of the coupled quantum dots is determined by that of small quantum dots. As a result, we found that the peak gain (123.9 ± 9.2 cm-1) with the 6 nm separation layer is comparable to that (125.2 ± 29.2 cm-1) of the small quantum dots with the 18 nm separation layer.

Modeling and simulation of the influence of quantum dots density on solar cell properties

Modeling and simulation of the influence of quantum dots density on solar cell properties

Optical Loss in Microdisk Lasers With Dense Quantum Dot Arrays

We discuss the origin of optical losses in microdisk lasers with a dense array of InGaAs quantum dots in the active region. In particular, we study the effect of microlaser diameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {D}$ </tex-math></inline-formula> variation from 15 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~\mu \text{m}$ </tex-math></inline-formula> on optical losses of different nature. A strong dependence of the lasing wavelength on the diameter is observed: the blue-shift with decreasing disk size implies an increase in optical losses, although in the case of an ideal cylinder, a noticeable optical loss should appear only at diameters comparable to the wavelength of light. A comparison of the spectral characteristics of microlasers with those of broad-area stripe lasers, for which optical loss can be easily found, gives a tool to evaluate optical loss in microdisk lasers, which was found to be unexpectedly high. It changes <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {\propto }\mathbf {D}^{\mathbf {-1}}$ </tex-math></inline-formula> from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 100$ </tex-math></inline-formula> cm−1 in the smallest microlasers to ~ 5 cm−1 in the largest ones. Several possible physical mechanisms of the appearance of optical losses in microlasers are considered, such as radiative loss due to the curvature of the cylindrical cavity, free carrier absorption, light scattering due to roughness of the side walls, and absorption of light in the near-surface region. The latter type of optical loss was found to be the dominant one and can explain the experimental results once the absorbing layer with a thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu \text{m}$ </tex-math></inline-formula> was suggested. Using the Gaussian approximation for Using the Gaussian approximation for the gain spectrum, the wavelength-loss relationship was simulated and a good agreement with the experimental dependence was found. The variation of the experimental results on optical loss for nominally identical microlasers was attributed to the variation of the scattering loss. The same reason can explain the scatter of the slope efficiency, which varies from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim ~0.03$ </tex-math></inline-formula> to 0.25 W/A being governed by the ratio of the scattering loss to the surface absorption loss.

High-temperature continuous-wave operation of 1310 nm InAs/GaAs quantum dot lasers

Here we report 1.3 μm electrical injection lasers based on InAs/GaAs quantum dots (QDs) grown on a GaAs substrate, which can steadily work at 110 °C without visible degradation. The QD structure is designed by applying the Stranski–Krastanow growth mode in solid source molecular beam epitaxy. The density of InAs QDs in the active region is increased from 3.8 × 1010 cm−2 to 5.9 × 1010 cm−2. As regards laser performance, the maximum output power of devices with low-density QDs as the active region is 65 mW at room temperature, and that of devices with the high-density QDs is 103 mW. Meanwhile the output power of high-density devices is 131 mW under an injection current of 4 A at 110 °C.

MOVPE grown InGaAs quantum dots with emission near 1.3 [formula omitted]m for electrically driven single-photon sources

InGaAs quantum dots (QDs) with low areal density suitable for single-photon applications are fabricated on a GaAs substrate by MOVPE. AFM measurements used to investigate the dependency of QD density and size on the V/III ratio during growth reveal a low QD density of 3.2⋅107cm−2 for a high V/III ratio of 360. To allow for a targeted electrical excitation, the InGaAs QDs are embedded into a pin-LED structure containing an oxide aperture. Low temperature electroluminescence measurements show emission of a QD line at a wavelength of 1272.4 nm. Direct comparison of photoluminescence and electroluminescence spectra approve the electrical excitation of a single QD.

Improving structure design of active region of InAs quantum dots by using InAs/GaAs digital alloy superlattice

A 1.3-μm InAs quantum dot laser has been successfully fabricated on a GaAs(100) substrate by molecular beam epitaxy (MBE) technique through using InAs/GaAs digital alloy superlattices instead of the conventional InGaAs layer. The samples grown by conventional growth method and the digital alloy superlattice growth method are characterized by atomic force microscope (AFM) and photoluminescence (PL) spectroscopy. It is found that 8-period sample possesses a low quantum dot density and poor luminescence performance. With the increase of the number of growth periods, the quantum dot density of the sample increases and the luminous performance improves. This indicates that the quality of the grown sample improves with the increase of InAs/GaAs period of the InGaAs layer. When the total InAs/GaAs period is 32, the quantum dot density of the sample is high and the luminescence performance is good. After the experimental measurement, the sample DAL-0 fabricated by conventional growth method and the sample DAL-32 (32-periods InAs/GaAs digital alloy superlattices) are utilized to fabricate quantum dot laser by standard process. The performances of two types of quantum dot lasers obtained with different growth methods are characterized. It is found that the InAs quantum dot lasers fabricated by the sample grown by digital alloy superlattice method have good performances. Under continuous wave operation mode, the threshold current is 24 mA corresponding to a threshold current density of 75 A/cm&lt;sup&gt;2&lt;/sup&gt;. The highest operation-temperature reaches 120 ℃. In addition, InAs quantum dot laser using digital alloy superlattice has good temperature stability. Its characteristic temperature is 55.4 K. Compared with the traditional laser, the InAs quantum dot laser grown by InAs/GaAs digital alloy superlattice has good performance in terms of threshold current density, output power and temperature stability, which indicates that high-quality laser can be obtained by this growth method. Using the InAs/GaAs digital alloy superlattice growth method, the InGaAs composition can be changed without changing the temperature of the source oven. Thus InAs quantum dot lasers with different luminescence wavelengths can be obtained through this growth method. The InAs/GaAs digital alloy superlattice structure can be used to realize different averaging of In content in the growth structure. The method provides a new idea for designing and growing the active region of quantum dot laser.

Facile microfluidic synthesis of monodispersed size-controllable quantum dot (QD) microbeads using custom developed QD photoresist.

Fluorescent microbeads (MBs) are widely used as next-generation biosensors for the detection of target chemicals at highly sensitive concentrations, and for imaging and tracking in vitro and in vivo. However, most known methods for producing fluorescent MBs require complicated multistep processes that result in low production rates. In this study, we report a method for fabricating micrometer-sized quantum dot microbeads (QD-MBs) using a microfluidic chip and specially designed QD photoresist (QD-PR). This on-demand lab-on-a-chip method yielded monodispersed QD-MBs ranging from 1.89 to 33 μm with a coefficient of variation of less than 10%. The size distribution of the fabricated QD-MBs was Gaussian with a peak around the mean diameter and a spread of sizes around the peak. Compared with nanoscale QDs, the fabricated QD-MBs showed no emission loss. The full-width at half-maximum of the emission peak of the QD-MBs was smaller than that of the colloidal QDs, indicating a more uniform distribution and a higher density of QDs within the MB structure. In addition, we investigated the microfluidic flow regime that yielded the most uniform and controllable QD-MB. The MBs in the dripping regime were spherical and monodisperse, with an excellent particle size distribution. In this study, we present a simple and effective strategy for producing QD-MBs with controllable sizes, which can be crucial in diverse fields such as biosensing, drug delivery, and imaging.

Atomic-scale characterization of single and double layers of InAs and InAlAs Stranski-Krastanov quantum dots

We report a detailed structural characterization of single and double layers of InAs and InAlAs quantum dots (QDs) and their wetting layers (WLs) by atomic force microscopy (AFM) and cross-sectional scanning tunneling microscopy (X-STM). The X-STM analysis with atomic resolution showed that the InAlAs WL consists of two distinct layers: a bottom part where all the Al atoms of the InAlAs alloy settled, and a top part containing exclusively In and Ga atoms. The QDs formed from the InAlAs layer contains no Al atoms at all and lie on top of the Al-rich WL. In the double layers of QDs, the InAlAs QDs were used as a seed to influence the nucleation of the InAs QDs grown on top. A gradual decrease in the density of the top InAs QDs was observed in the AFM images with increasing thickness of the GaAs spacer. The X-STM images showed that both QDs layers were completely intermixed for a 2-nm-thick spacer, while effective strain-induced stacking of both types of QDs was observed for a GaAs spacer thickness of 4 nm. However, both QD layers were completely decoupled for a GaAs spacer thickness of 8 nm and could thus be treated as individual layers.

Magnetic/fluorescent dual-modal lateral flow immunoassay based on multifunctional nanobeads for rapid and accurate SARS-CoV-2 nucleocapsid protein detection

The SARS-CoV-2 pandemic has posed a huge challenge to rapid and accurate diagnosis of SARS-CoV-2 in the early stage of infection. In this work, we developed a novel magnetic/fluorescent dual-modal lateral flow immunoassay (LFIA) based on multifunctional nanobeads for rapid and accurate determination of SARS-CoV-2 nucleocapsid protein (NP). The multifunctional nanobeads were fabricated by using polyethyleneimine (PEI) as a mediate shell to combine superparamagnetic Fe3O4 core with dual quantum dot shells (MagDQD). The core-shell structure of MagDQD label with high loading density of quantum dots (QDs) and superior magnetic content realized LFIA with dual quantitative analysis modal from the assemblies of individual single nanoparticles. The LFIA integrated the advantages of magnetic signal and fluorescent signal, resulting excellent accuracy for quantitative analysis and high elasticity of the overall detection. In addition, magnetic signal and fluorescent signal both had high sensitivity with the limit of detection (LOD) as 0.235 ng mL−1 and 0.012 ng mL−1, respectively. The recovery rates of the methods in simulated saliva samples were 91.36%–103.60% (magnetic signal) and 94.39%–104.38% (fluorescent signal). The results indicate the method has a considerable potential to be an effective tool for diagnose SARS-CoV-2 in the early stage of infection.

Demonstration of in-plane miniband formation in InAs/InAsSb ultrahigh-density quantum dots by analysis of temperature dependence of photoluminescence

Self-assembled InAs/InAsSb ultrahigh-density quantum dots (UHD QDs) were grown on GaAs(001) substrate by molecular beam epitaxy. The QD density was 1 × 1012 cm−2, and an average separation distance between adjacent QD edges was less than 3 nm. The temperature dependence of photoluminescence (PL) minimum energy of UHD QDs was measured and was divided clearly into three temperature regions: (1) fitting to upper Varshni shift at 15–80 K, (2) decreasing from upper Varshni shift from 80–180 K and (3) re-fitting to lower Varshni shift at 180–290 K. The energy difference between upper and lower Varshni curves increased with increasing QD density. This anomalous temperature dependence of PL minimum energy was demonstrated by a simulation model of miniband formation due to electronically strong coupling of adjacent QDs, including the temperature dependence of the homogeneous broadening in the QD.

Enhanced Photoluminescence of 1.3 μm InAs Quantum Dots Grown on Ultrathin GaAs Buffer/Si Templates by Suppressing Interfacial Defect Emission.

We report on the photoluminescence enhancement of 1.3 μm InAs quantum dots (QDs) epitaxially grown on an ultrathin 250 nm GaAs buffer on a Si substrate. Decreasing the GaAs buffer thickness from 1000 to 250 nm was found to not only increase the coalesced QD density from 6.5 × 108 to 1.9 × 109 cm-2 but also decrease the QD photoluminescence emission intensity dramatically. Inserting an Al0.4Ga0.6As potential barrier layer maintained strong photoluminescence from the QDs by effectively suppressing carrier leakage to the GaAs/Si interfacial region even when the GaAs buffer was thinned to 250 nm. We then fabricated a light-emitting diode using the ultrathin 250 nm GaAs buffer on Si and confirmed strong electroluminescence peaking at 1.28 μm without interfacial defect emission at room temperature. We believe that this work is promising for monolithically integrated evanescent Si lasers using InAs/GaAs QDs.

Drastic photostability improvement of silica particles impregnated with multiple emitting CdSe quantum dots prepared through efficient surface silanization

Numerous studies have been performed on silica coated quantum dots (QDs) for the retention of photostability of QDs over long period of time. However, the photostability of silica coated QDs has been found to be inferior to that of polymer coated QDs under some circumstances, and the quantitative data is missing in prior arts. Here, we report the drastic improvement of photostability of CdSe QDs encapsulated into silica particles by optimizing the preparation conditions. We have prepared silica particles (ca. 60 nm in size) encapsulated with multiple, over dozens of emitting CdSe QDs. The key step is a surface silanization of QDs, where the original ligands are replaced by a partially hydrolyzed alkoxide in hydrophobic solution. The evaluation using single particle detection methods shows that the photostability increases up to 8 times as compared with the polymer coated counterparts by optimizing the molar ratio of alkoxide against QDs upon the silanization. When the ratio is optimum, the packing density of QDs in the silica particle becomes the maximum accompanied by the most obvious red shift of ensemble photoluminescence peak. This indicates a developed silica network in close proximity to the QD surface on the particle is formed. The knowledge acquired from this work is universal, and can be extended to other emitting QDs such as InP and perovskites.

Emission Variation of InAs Quantum Dots within (Al)GaInAs Quantum Wells in AlGaAs/GaAs Structures vs Quantum Well Compositions

The parameters of quantum dots (QDs) of InAs inserted in Al0.30Ga0.70As/GaAs hetero structures with additional cap/buffer AlGaInAs quantum wells (QWs) of different compositions have been investigated by photoluminescence, transmission electron microscopy and high-resolution X-ray diffraction methods. QD structures with the buffer layers: In0.15Ga0.85As (#1) or In0.25Ga0.75As (#2) and covering (cap) layers: Al0.10In0.15Ga0.75As (#1) or Al0.40In0.15Ga0.45As (#2), are compared. Structure #1 is characterized by a higher density of QDs, high QD emission intensity and a smaller full width at half maximum of the PL bands, compared to #2. The dependence of the intensity of QD emission against temperatures of 10–500 K has been studied. Significant thermal quenching of the PL intensity was revealed in #1 compared to #2. HR-XRD investigation has confirmed that QD structures are of perfect crystalline quality with sharp QW interfaces and a high number of Pendellösung peaks were detected. To fit the HR-XRD scans, the X′Pert Epitaxy software has been applied. The peculiarities of the QD emission and the parameters of the HR-XRD scans are compared, as well as the advances of the QD structures studied are discussed.

Analytical Model and Experimental Analysis to Estimate the Interdiffusion and Optoelectronic Properties of Coupled InAs Quantum Dots Post Rapid Thermal Processing

The stoichiometric variations in molecular beam epitaxy (MBE)-grown In(Ga)As quantum dots (QDs) after rapid thermal processing (RTP) is estimated from an analytical model assisted by transmission electron microscopy (TEM) images. A systematically grown multilayer (bi-, penta-, hepta-, and deca-layer) InAs Stranski–Krastanov (SK) QDs coupled electronically to submonolayer (SML) QDs are used in this study. The As-grown (ASG) samples are treated with RTP at temperatures of 650 °C, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$700~^{\circ }\text{C}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$750~^{\circ }\text{C}$ </tex-math></inline-formula> , and 800 °C for 30 s. Our model estimates a significant diffusion of In atoms in the growth direction compared with the in-plane direction altering the QD dimensions and composition. To check its reliability, we incorporated an eight-band k.p model on all the RTP-treated strained In(Ga)As QD heterostructures. Photoluminescence (PL) measurements reveal a strong correlation with the simulation results; furthermore, a strong PL blueshift (56 nm) and narrow linewidth from 67 nm (ASG) to 33 nm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$800~^{\circ }\text{C}$ </tex-math></inline-formula> ) are seen due to an increase in the uniformity of QDs supporting the atomic force microscopy (AFM) results. AFM images reveal the formation of highly uniform and dense QDs with increased annealing temperature. The activation energy (AE) shows a decreasing trend due to the reduction in carrier confinement with RTP, agreeing with the analytical model. This is probably the first report that presents the effect of RTP on SK-SML coupled QD devices both in terms of theoretical and experimental analyses. This analytical model can thus be extended to any annealing study and for any material with certain known parameters and is helpful for futuristic studies.

Full wafer property control of local droplet etched GaAs quantum dots

We present strategies for controlling growth parameters of local droplet etched GaAs quantum dots. We manage the local QD density and emission wavelength by gradient material deposition. We find regions with no light-emitting quantum dots sharply separated from regions with strong quantum dot luminescence. Close to this transition, we expect the lowest quantum dot densities possible under the used parameters. The maximum wavelength shift achieved due to a variation of GaAs hole filling level on a single 3-inch wafer ranges from 731to 795 nm. By locally controlling the surface roughness, a profound additional influence on the emission wavelength and density is found. We show how to control this modulation on a millimeter-scale over the whole wafer.