Metrology for III-V optosemiconductors: Dissertation

Hans Baumgartner

Research output: ThesisDissertationCollection of Articles


Light-emitting diodes (LEDs) are III-V compound semiconductors manufactured by combining elements from group III (such as Al, Ga, and In) with elements from group V (such as N, P, As), forming compounds like GaN, GaInAs, and AlInP. High-power white LEDs are manufactured by coating a blue or an ultraviolet (UV) LED with phosphor, absorbing part of the blue/UV photons and emitting them at higher wavelengths. High-power LEDs are typically packaged to form an optosemiconductor device with a power rating between 1 and 5 W. In addition to light-emitting devices, III-V optosemiconductor devices can be utilized as photon absorbing, multi-junction solar cells. The materials and manufacturing processes for LEDs and III-V solar cells are the same, making their electrical and optical properties similar. In this thesis, measurement setups and novel analysis methods have been developed for luminous efficacy, lifetime, and band gap energy of LEDs and multi-junction solar cells manufactured using III-V materials. The lifetime of high-power LEDs was studied by aging different types of LED lamps at room temperature and at elevated temperatures of 45 °C and 60 °C. The aging was measured as the change of luminous flux over time. The aging accelerated on the average by factors of 1.35 and 2.36 when aging the LEDs at the elevated temperatures. The lifetime of high quality LEDs was shown to be more than 50 000 hours and projected with a new method to exceed 100 000 hours. Despite the high efficiency of LEDs, most of the consumed electrical power is still wasted in the form of heat, weakening the lifetime and optical characteristics of the optosemiconductor devices. To study the effect of temperature on the optical characteristics of high-power LEDs and multijunction solar cells, a temperature controller based on liquid cooling and resistive heating was designed and built. A novel model for the emission spectrum of an LED was developed to determine the band gap energy of the device under tests. The method was shown to work in determining the alloy composition of III-V LEDs. The method was tested and utilized to determine the band gap energies of III-V multi-junction solar cells as well. The developed method can be used to determine temperature-invariant band gap characteristics of all III-V optosemiconductor devices.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
  • Ikonen, Erkki, Supervisor
  • Kärhä, Petri, Advisor, External person
Award date9 Jun 2017
Place of PublicationEspoo
Print ISBNs978-952-60-7472-6, 978-951-38-8543-4
Electronic ISBNs978-952-60-7471-9, 978-951-38-8542-7
Publication statusPublished - 2017
MoE publication typeG5 Doctoral dissertation (article)


  • band gap
  • lifetime
  • light-emitting diode
  • radiometry
  • solar cell


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