Recombination Dynamics in GaN/AlGaN Low Dimensional Structures Obtained by SiH4 Treatment

Krzysztof P. Korona 2Barbara Chwalisz 2Andrzej Wysmołek 2Roman Stępniewski 2Krzysztof Pakuła 2Jacek Baranowski 2Jürgen Kuhl 1

1. Max-Planck-Institut FKF, Heisenbergstr. 1, Stuttgart D70569, Germany
2. Warsaw University, Institute of Experimental Physics (IEP UW), Hoża 69, Warszawa 00-681, Poland

Abstract

We present optical properties of low dimensional quantum dot-like GaN/AlGaN structures, which were obtained in a low-pressure MOVPE reactor. A primarily grown AlGaN layer had been exposed to SiH4. On the SiH4-treated surface GaN grew on distinctly separated island sites and was capped with a second AlGaN layer.
Photoluminescence (PL) shows two bright PL bands (P1, P2) and one weak (P3) PL band at energies of 3.48 eV, 3.44 eV and 3.35 eV, respectively. Micro-photoluminescence measurements reveal that these bands consist in fact of many sharp lines coming from small spots on the sample. Such behavior is characteristic for quantum dots or islands.
Time-resolved PL shows that the P1, P2 and P3 bands have lifetimes of about 0.1 ns, 0.5 ns and 1.3 ns, respectively. The P2 and P3 bands show significant spectral shifts with time. For example, the P2 band shifts from 3.445 eV at t = 0.1 ns down to 3.430 eV at t = 2.5 ns. As confirmed by power dependent measurements, the spectral shifts are partially due to state filling effects. State filling is usually observed in QDs due to their low density of states. During few hundreds of ps, electrons relax from higher to lower states and the average energy of the QD band decreases with time. Then PL emission from the ground states of QDs can be measured and analyzed. For the P2 band, at about 3.43 eV, a ground state decay rate of about 2.4 ns-1 has been determined.
Temperature dependent PL measurements show S-shape dependence of the PL energy vs temperature for the P2 band. On the other hand, the P1 peak shifts monotonically to lower energy in agreement with the energy band-gap shrinkage. The time-resolved measurement shows the mechanism of this effect. Up to 50 K, increase of temperature leads only to promotion of some electrons to high-energy states. But above 50 K the decays are faster due to the thermal escape of carriers. Since the thermal escape is faster in the case of high-energy states, the average PL energy decrease.

Related papers
  1. (Cd, Mn)Te Crystals for X and Gamma Radiation Detectors - an Alternative Material to CdTe and (Cd,Zn)Te. 
  2. Growth and properties of inclined GaN nanowires on Si(001) substrates by PAMBE
  3. Safe nanomaterials of spinel structure for lithium-ion secondary batteries 
  4. Optical Characterisation of Bulk ZnO Crystals Grown by CVT
  5. Physical properties of unique ZnO single crystals from Oława Foundry
  6. Impact of internal electric fields for GaInN/GaN quantum wells in light emitting diodes
  7. Influence of  SiC substrate orientation on epitaxial graphene quality studied by Raman spectroscopy
  8. Pinned and unpinned epitaxial and sublimated graphene on SiC
  9. Synthesis and studies on LiMn2O4/Carbon nanocomposites as a cathode materials for lithium ion batteries
  10. Graphene epitaxy by chemical vapor deposition on SiC.
  11. Raman spectroscopy of single and multilayer graphene on SiC substrates
  12. 2D and 3D growth mode of nitride layers
  13. Optical properties of p-type ZnO:(N, As, Sb)
  14. Spontaneous Superlattice Formation in MOCVD Growth of AlGaN
  15. Anomalous behaviour of the photoluminescence from GaN/AlGaN quantum wells
  16. Electroreflectance and photoreflectance studies of AlGaN/GaN heterostructure with a QW placed inside AlGaN layer
  17. Optical Detection of 2DEG in GaN/AlGaN Structures - High Magnetic Field Studies
  18. Light induced contrast in Kelvin Force Microscopy of GaN epilayers

Presentation: poster at E-MRS Fall Meeting 2004, Symposium C, by Krzysztof P. Korona
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-28 09:41
Revised:   2009-06-08 12:55
Google
 
Web science24.com
© 1998-2018 pielaszek research, all rights reserved Powered by the Conference Engine