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Room-temperature operation of transistor vertical-cavity surface-emitting laser
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
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2013 (English)In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 49, no 3, 208-209 p.Article in journal (Refereed) Published
Abstract [en]

The first room-temperature operation of a transistor vertical-cavity surface-emitting laser (T-VCSEL) is demonstrated. Fabricated using an epitaxial regrowth process, the T-VCSEL is electrically a pnp-type bipolar junction transistor and consists of an undoped AlGaAs/GaAs bottom DBR, an InGaAs triple-quantum-well active layer, an Si/SiO2 dielectric top DBR, and an intracavity contacting scheme with three electrical terminals. The output power is controlled by the base current in combination with the emitter-collector voltage, showing a voltage-controlled operation mode. A low threshold base-current of 0.8 mA and an output power of 1.8 mW have been obtained at room temperature. Continuous-wave operation was performed up to 50 degrees C.

Place, publisher, year, edition, pages
2013. Vol. 49, no 3, 208-209 p.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-122993DOI: 10.1049/el.2012.4243ISI: 000318542500030Scopus ID: 2-s2.0-84877727168OAI: oai:DiVA.org:kth-122993DiVA: diva2:624265
Funder
Swedish Research Council
Note

QC 20130605

Available from: 2013-05-30 Created: 2013-05-30 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Developments for Improved Performance Vertical-Cavity Surface Emitting Lasers
Open this publication in new window or tab >>Developments for Improved Performance Vertical-Cavity Surface Emitting Lasers
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The vertical-cavity surface-emitting laser (VCSEL) is a type of laser diode that emits light from the surface of the chip from which it is manufactured rather than from a cleaved edge as so far has been common for most telecommunication lasers. VCSEL’s low cost, high power efficiency and low power consumption properties make it a very attractive signal source for many applications such as fiber optical communication, optical interconnects, 3D sensing, absorption spectroscopy, laser printing, etc.

In this work, we have developed and evaluated new designs and technologies for extending the performance of VCSELs based on the GaAs material system. A novel scheme for single-mode emission from large size VCSELs, with active region size up to 10 μm, is proposed and discussed. Oxide-free designs of the VCSEL structure either based on an epitaxially regrown p-n-p layer or a buried tunnel junction (BTJ) for lateral current confinement are fabricated and characterized; the latter scheme yielding significant dynamic and static performance improvement as compared to epitaxially regrown design. In addition, the first room-temperature operation of a heterojunction bipolar transistor (HBT) 980nm VCSEL, a so-called transistor-VCSEL, is demonstrated. This novel three-terminal operational VCSEL is believed to have the potential for a ultrahigh modulation bandwidth due to altered carrier dynamics in the cavity region.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 61 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:11
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-146641 (URN)978-91-7595-164-5 (ISBN)
Presentation
2014-06-13, Sal/hall D, KTH-ICT, Isafjordgatan 39, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20140612

Available from: 2014-06-12 Created: 2014-06-12 Last updated: 2014-06-13Bibliographically approved
2. GaAs based Vertical-Cavity Surface-Emitting Transistor-Lasers
Open this publication in new window or tab >>GaAs based Vertical-Cavity Surface-Emitting Transistor-Lasers
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The ever-increasing demand for broadband capacity of the global optical communication networks puts enormous requirements on the semiconductor laser used in the optical transmitter. Industrial standard bodies for optical communication project requirements of single-channel data rates as high as 100 Gbit/s around year 2020. This is a significant step with respect to today's technology which is only at the verge of introducing 25 Gbit/s emitters. The preferred light source for these applications is the vertical-cavity surface-emitting laser (VCSEL) which can offer cost- and power-efficient directly modulated operation. However, it has proven extremely difficult to push the modulation bandwidth of VCSELs beyond 30 GHz and radically new device concepts are demanded to meet the upcoming needs. One such new device paradigm consists of the transistor laser which is the fusion of a semiconductor laser and a high-speed heterojunction bipolar transistor (HBT) into a single device, with potential significant advantages in modulation bandwidth, noise properties and novel functionality by virtue of the three-terminal configuration. The present thesis deals with the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs), a device previously not realized or investigated in great detail.

GaAs-based T-VCSELs are investigated both theoretically and experimentally. A three-dimensional model is set up with a commercial software package and used for performance predictions and analysis as well as design and optimization purposes. It is concluded that a T-VCSEL biased in the common-base configuration may have a bandwidth surpassing those of conventional diode-type VCSELs or a T-VCSEL itself in the common-emitter configuration. Fabricated T-VCSELs make use of an epitaxial regrowth design to homogeneously integrate an AlGaAs/GaAs HBT and an InGaAs/GaAs VCSEL. An intracavity contacting scheme involving all three terminals, undoped distributed Bragg reflectors and modulation doping are used to ensure a low-loss laser structure. The first generation of devices showed sub-mA range base threshold current in combination with a high output power close to 2 mW but did not fulfill the requirements for a fully operational transistor laser since the transistor went into saturation before the onset of lasing (IBsat<IBth). From numerical simulations this premature saturation was demonstrated being due to a lateral potential variation within the device and large voltage drops along the base and collector regions. As a remedy to this problem the base region was redesigned for a reduced resistance and transistor current gain, and the saturation current could thereby be extended well beyond threshold. These devices showed excellent transistor-laser characteristics with clear gain-compression at threshold, mA-range base threshold current, mW-range output power, high-temperature operation to at least 60°C, low collector-emitter offset voltage and record-low power dissipation during lasing. Furthermore, the collector-current breakdown characteristics was investigated in some detail and it is concluded that this, in contrast to previous models, presumably not is due to an intracavity photon reabsorption process but rather to a quantum-well band-filling effect.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. vii, 64 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:16
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-156841 (URN)978-91-7595-363-2 (ISBN)
Public defence
2014-12-19, Sal/hall C, Electrum, KTH-ICT, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20141203

Available from: 2014-12-03 Created: 2014-12-02 Last updated: 2015-04-13Bibliographically approved

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Hammar, Mattias

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