Chromaticity and electroluminescent efficiency of atomic layer epitaxy SrS:Ce thin films
- Sandia National Laboratories, Albuquerque, New Mexico 87185-1349 (United States)
- Planar International Ltd., Olarinluoma 9, P.O. Box 46, SF-02201Espoo (Finland)
- Laboratoire dOptique des Solides, Universite Pierre et Marie Curie, Case 80, 75252 Paris Cedex 05 (France)
- Planar America Inc., Beaverton, Oregon 97006 (United States)
We have studied various factors that control the luminous properties of atomic layer epitaxy (ALE) SrS:Ce electroluminescent (EL) devices by using electron paramagnetic resonance, photoluminescent decay, x-ray diffraction, and charge-voltage characterization. EL and PL light is green shifted in ALE SrS:Ce films, compared to powders and thin films prepared with some other techniques. The origin of the green shift is discussed. Moderate heat treatments of as-deposited SrS:Ce devices were found to dramatically improve the EL efficiency. This is due to the removal of defects leading to nonradiative Ce{sup 3+} decay and to reduction of Ce{sup 4+} to radiative Ce{sup 3+}. Different heat treatments were found to influence the transferred charge, so that there is an optimal heat treatment temperature between 500 and 750{degree}C. Heat treatments also induce macroscopic stress in these SrS:Ce films. This was seen to induce a local stress around Ce{sup 3+} sites. However, the stresses were not found to directly correlate with the luminous efficiency. The SrS:Ce growth temperature was found to affect the Ce{sup 3+} excitation efficiency in EL. Electronic traps in SrS:Ce films are discussed. We suggest that some traps can be beneficial in providing necessary charge for the Ce{sup 3+} excitation process and others can be deleterious in that they suppress radiative Ce{sup 3+} decay events. To determine the effects of Ce doping, undoped SrS films were also deposited and fully characterized. Finally, we compare the properties of films prepared by ALE to those deposited via rf sputtering. {copyright} {ital 1998 American Institute of Physics.}
- OSTI ID:
- 613978
- Journal Information:
- Journal of Applied Physics, Vol. 83, Issue 5; Other Information: PBD: Mar 1998
- Country of Publication:
- United States
- Language:
- English
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