Fig 3 - uploaded by Hao-Chung Kuo
Content may be subject to copyright.
Source publication
This paper presents the fabrication and characteristics of high-performance 850-nm InGaAsP-InGaP strain-compensated multiple-quantum-well (MQW) vertical-cavity surface-emitting lasers (VCSELs). The InGaAsP-InGaP MQW's composition was optimized through theoretical calculations, and the growth condition was optimized using photoluminescence. These VC...
Context in source publication
Context 1
... schematic structure of a fabricated top emitting VCSEL is shown in Fig. 3, which has been grown by low-pres- sure metal organic chemical vapor deposition (MOCVD) on a semi-insulating (100) 100 SC-MQWs surrounded by a cladding layer to cavity. A 30-nm-thick was introduced on the upper cavity spacer layer to form an oxide confinement. Finally, thickness of the current spreading layer and heavily doped GaAs cm ...
Similar publications
Loss between elements of coherently coupled vertical-cavity surface-emitting laser (VCSEL) arrays typically causes out-of-phase operation with on-axis intensity nulls in the far-field. We show that in-phase evanescently coupled VCSEL arrays may be defined by proton implantation. An advantage for implanted in-phase coherently coupled VCSEL arrays is...
Long-wavelength InAlGaAs VCSELs with Al<sub>2</sub>O<sub>3</sub> embedded current-confinement structures are reported. Using atomic layer deposition, the current confinement structures are fabricated by depositing Al<sub>2</sub>O<sub>3</sub> on airgap surfaces of undercut apertures, which are formed by laterally etching the active region. 1.57 μm V...
We report, for the first time, InP-based all-epitaxially grown 1.3-/spl mu/m vertical-cavity surface-emitting lasers with lattice-matched Sb-based distributed Bragg reflectors and AlInAs etched apertures. The minimum threshold current and voltage under pulsed operation were 3 mA and 2.0 V, respectively. The thermal impedance was as low as 1.2 K/mW...
We compare experimental data with three-dimensional numerical calculations of the local minority current in an InGaAs/GaAs transistor vertical-cavity surface-emitting laser at different bias levels. It is demonstrated that lateral potential variations within the device greatly affect the transistor operating conditions. As a result, it locally oper...
In this paper, work is described on the fabrication of highly uniform 8/spl times/8 arrays of GaAs-AlGaAs vertical-cavity surface-emitting lasers (VCSEL's). Oxide-confined VCSEL arrays show an average threshold current of 0.74/spl plusmn/0.02 mA, an average output power of 2.05/spl plusmn/0.03 mW at 8 mA and an average power conversion efficiency o...
Citations
... An additional difficulty concerns the interfaces between GaInP/InGaAsP and InGaAsP/GaInP at the QW where indium carryover [20,21] and arsine-phosphine exchange [22] can occur and reduce the optical performance. ...
We demonstrate a deep-red-emitting vertical external-cavity surface-emitting laser (VECSEL) with an emission wavelength around λ = 765 nm based on InGaAsP/GaInP quantum wells. The quaternary material system was characterized with x-ray diffraction of thin films as the basis for InGaAsP quantum wells, which are incorporated into an 11 × 1 quantum well active region. The surface morphology of the fabricated VECSEL structure is analyzed with atomic force microscopy and the laser is evaluated in a linear cavity for various heatsink temperatures resulting in a watt-level output power of Pmax,−15°C = 1.71 W in a fundamental transverse mode.
... Optimization of the CS value in the active layer and implementation of strain-compensated InGaAsP/GaAsP/AlGaAs-active regions are expected to further improve device performance. Recently, Chang et al. (2004) have also implemented the straincompensated In 0.18 Ga 0.82 As 0.8 P 0.2 QW with tensile barriers of 100-ÅIn 0.4 Ga 0.6 P into active regions for VCSELs with improved reliability, high-speed performance, and threshold characteristics. ...
Quantum-well (QW) active semiconductor lasers enjoy widespread commercial use in optoelectronic applications ranging from high-power sources for medical therapy, material processing, laser printing, and pumps for solid-state lasers to lower output power single-mode, single-frequency sources for telecommunications. Strained-layer QWs, such as InGaAs/GaAs and InGaAs/InP, have become the workhorse materials for near-infrared diode laser sources. More recently, the large energy band gap bowing in dilute nitride materials is further opening up the emission wavelength windows, which is otherwise limited by material strain relaxation. This chapter reviews QW laser design issues and general properties of QW lasers. Applications of QW active regions to realize high output power, long emission wavelength, and visible emission from InGaN/GaN QW lasers are discussed.
... This causes a red shift of the gain-peak, which in turn has to be compensated by increasing the Al content in the barrier layers and by reducing the QW width [7]. However, a reduced QW width enhances carrier leakage [14] , the magnitude of which worsens with increasing device temperatures, thereby limiting the high-speed operation [15]. High-speed operation of VCSELs is achieved by reducing the cavity photon lifetime [8], increasing the differential gain [13], and reducing the gain-compression coefficient by optimizing the separate-confinement heterostructure (SCH) for a short carrier capture time [9]. ...
We study the impact of device parameters, such as inner-aperture diameter and cavity photon lifetime, on ther-mal rollover mechanisms in 850-nm, oxide-confined, vertical-cavity surface-emitting lasers (VCSELs) designed for high-speed operation. We perform measurements on four different VCSELs of different designs and use our empirical thermal model for calculating the power dissipated with increasing bias currents through various physical processes such as absorption within the cavity, carrier thermalization, carrier leakage, spontaneous carrier recombination, and Joule heating. When reducing the top mirror reflectivity to reduce internal optical absorption loss we find an increase of power dissipation due to carrier leakage. There is therefore a trade-off between the powers dissipated owing to optical absorption and carrier leakage in the sense that overcompensating for optical absorption enhances carrier leakage (and vice versa). We further find that carrier leakage places the ultimate limit on the thermal performance for this entire class of devices. Our analysis yields useful design optimization strategies for mitigating the impact of carrier leakage and should thereby prove useful for the performance enhancement of 850-nm, high-speed, oxide-confined VCSELs.
... Among the merits of VCSELs include their circular output beam, low power consumption, and low manufacturing cost. VCSELs fabricated on GaAs substrates have been expected to be high-performance and cost-effective light sources [1], [2]. Semiconductor lasers whose active regions contain quantum dots (QDs) have been demonstrated to have excellent characteristics , such as low threshold currents, low chirp, high differential gain, and insensitivity to temperature [3], [4]. ...
... The incorporation of In into GaAs quantum wells (QWs) had been demonstrated to provide com- pressive strain, which, in turn, resulted in lower threshold current and higher modulation speed [12], [13]. Previous research also showed that the InGaAsP, which was used during most of the initial development of long-wavelength VCSELs, could provide comparable laser performance [5], [14]- [16]. It is well known that low transparency current achievable with strained QWs is required for providing low threshold current in a semiconductor laser. ...
In this study, the gain-carrier characteristics of In<sub>0.02</sub>Ga<sub>0.98</sub>As and InAlGaAs quantum wells (QWs) of variant In and Al compositions with an emission wavelength of 838 nm are theoretically investigated. More compressive strain, caused by higher In and Al compositions in InAlGaAs QW, is found to provide higher material gain, lower transparency carrier concentration, and transparency radiative current density over the temperature range of 25-95°C. To improve the output characteristics and high-temperature performance of 850-nm vertical-cavity surface-emitting laser (VCSEL), In<sub>0.15</sub>Al<sub>0.08</sub>Ga<sub>0.77</sub>As/Al<sub>0.3</sub>Ga<sub>0.7</sub>As is utilized as the active region, and a high-bandgap 10-nm-thick Al<sub>0.75</sub>Ga<sub>0.25</sub>As electronic blocking layer is employed for the first time. The threshold current and slope efficiency of the VCSEL with Al<sub>0.75</sub>Ga<sub>0.25</sub>As at 25°C are 1.33 mA and 0.53 W/A, respectively. When this VCSEL is operated at an elevated temperature of 95°C, the increase in threshold current is less than 21% and the decrease in slope efficiency is approximately 24.5%. A modulation bandwidth of 9.2 GHz biased at 4 mA is demonstrated.
Vertical Cavity Surface Emitting Laser (VCSEL)-based data links are attractive due to their low-power dissipation and low-cost manufacturability. This chapter reviews the foundations for this technology, as well as the device and module design challenges of extending the data rate beyond the current level. We begin with a review of data communications from the business perspective, and continue with a brief discussion of the current and future standards. This is followed by a survey of recent advances in VCSELs, including data links operating at 28 Gb/s. We review the recent efforts on ultra-fast data links and discuss the advantages of the different approaches. We also examine key design aspects of optical transceiver modules and we focus our discussion on novel applications in high-performance computing using both multi-mode and single-mode fiber optics. We highlight the importance of the device/component-level and system-level modeling and show some modeling examples with comparison to measured data. We conclude with a comparison of the VCSEL-based data links with other competing technologies, including silicon photonics and short-cavity edge emitting lasers.
We present an empirical thermal model for VCSELs based on extraction of
temperature dependence of macroscopic VCSEL parameters from CW
measurements. We apply our model to two, oxide-confined, 850-nm VCSELs,
fabricated with a 9-μm inner-aperture diameter and optimized for
high-speed operation. We demonstrate that for both these devices, the
power dissipation due to linear heat sources dominates the total
self-heating. We further show that reducing photon lifetime down to 2 ps
drastically reduces absorption heating and improves device static
performance by delaying the onset of thermal rollover. The new thermal
model can identify the mechanisms limiting the thermal performance and
help in formulating the design strategies to ameliorate them.
In this paper, we employed a high bandgap Al0.75Ga0.25As layer acting as an electronic blocking layer in the upper In0.15Al0.08Ga0.77As/Al0.3Ga0.7As active region before the growth of p-type layers of 850-nm vertical-cavity surface-emitting lasers (VCSELs). A threshold current of 1.33 mA and slope efficiency of 0.53 W/A at 25°C were obtained, and the temperature dependent light output and voltage versus current (L-I-V) characteristics showed that the VCSELs with a high bandgap Al0.75Ga0.25As layer were more stable when the substrate temperature was in a range of 25--95°C. The threshold current increased with temperature up to 95°C was less than 21% and the slope efficiency dropped only 24.5%.
In this study, the carrier blocking effect on 850 nm InAlGaAs/AlGaAs vertical-cavity surface-emitting layers (VCSELs) was theoretically and experimentally investigated. By means of inserting a high-bandgap electron blocking layer, which was either 10 nm thick Al 0.75 Ga 0.25 As or 13 nm thick Al 0.9 Ga 0.1 As, on the p-side of a quantum-well active region, the laser output performance was theoretically found to be improved. VCSELs with and without an electron blocking layer were also experimentally demonstrated. It was found that the threshold current was reduced from 1.47 to 1.33 mA and the slope efficiency was increased from 0.37 to 0.53 mW mA −1 by inserting a 10 nm thick Al 0.75 Ga 0.25 As electron blocking layer. Also, the device became less sensitive to the device temperature, where the amount of increase in the threshold current at an elevated temperature of 95 • C was only 0.27 mA and the slope efficiency dropped by only 24.5%. A peak frequency response of nearly 9 GHz at 5 mA, measured from relative intensity noise (RIN), was obtained in these VCSEL devices.
The physical and optical properties of compressively strained InGaAsP/InGaP quantum wells for 850-nm vertical-cavity surface-emitting
lasers are numerically studied. The simulation results show that the maximum optical gain, transparency carrier densities,
transparency radiative current densities, and differential gain of InGaAsP quantum wells can be efficiently improved by employing
a compressive strain of approximately 1.24% in the InGaAsP quantum wells. The simulation results suggest that the 850-nm InGaAsP/InGaP
vertical-cavity surface-emitting lasers have the best laser performance when the number of quantum wells is one, which is
mainly attributed to the non-uniform hole distribution in multiple quantum wells due to high valence band offset.
