Loading...
News About Joachim Piprek

What is to blame for the low energy efficiency of GaN-based lasers?

  • Oct 31, 2017 |

    Nobel laureate Shuji Nakamura predicted in 2014 that GaN-based laser diodes are the future of solid state lighting, which is thus far mainly driven by the high energy efficiency of GaN-based LEDs. However, GaN-lasers still exhibit a relatively low energy efficiency...

     

    Nobel laureate Shuji Nakamura predicted in his Nobel lecture that GaN-based laser diodes are the future of solid state lighting. However, GaN-lasers still exhibit only about 40% power conversion efficiency while some GaN-LEDs exceed 80%. This article reviews the origins of this efficiency deficit and presents a promising remedy.

    GaN-basedlaserdiodestransformonlyarelativelysmallfractionoftheelec-
    tricalinputpowerintolaserlight.Theinherentlylargeseriesresistanceofthesedevices
    causessigniï¬cantself-heatingthatleadstothetypicalpowerroll-offathighcurrent.We
    analyzerecentlyreportedmeasurementsusingadvancednumericallasersimulationand
    investigatethephysicalmechanismsthatlimitthelasingpowerincontinuous-wave
    operation.Contrarytocommonexpectations,ouranalysisrevealsastronginfluenceof
    Augerrecombinationsincetheself-heatingleadstoarisingquantumwellcarrierdensity
    abovethelasingthreshold.Aspossibleremedy,weinvestigatetheeffectofatunnel-
    junctioncontactandpredictasigniï¬cantenhancementoflasingpowerandefï¬ciency.GaN-based laser diodes transform only a relatively small fraction of the electrical input power into laser light. The inherently large series resistance of these devices causes significant self-heating that leads to the typical power roll-off at high current. We analyze recently reported measurements using advanced numerical laser simulation and investigate the physical mechanisms that limit the lasing power in continuous-wave operation. Contrary to common expectations, our analysis reveals a strong influence of Auger recombination since the self-heating leads to a rising quantum well carrier density above lasing threshold. As possible remedy, we investigate the effect of a tunnel-junction contact and predict a significant enhancement of lasing power and efficiency.
    See More
    Subjects
    Engineering - Electrical, Materials Science, Mathematics, Nanoscience & Technology, Physics