High Luminescence Efficiency from GaAsN Layers Grown by MBE with RF Nitrogen Plasma Source
- PDF / 376,650 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 39 Downloads / 172 Views
High Luminescence Efficiency from GaAsN Layers Grown by MBE with RF Nitrogen Plasma Source. 1*
Victor M. Ustinov, Nikolai A. Cherkashin, Nikolai A. Bert, Andrei F. Tsatsul’nikov, Alexei R. Kovsh , 1
1
1
Jyh-Shang Wang , Li Wei , and Jim Y. Chi A.F.Ioffe Physco-Technical Institute, St.Petersburg 194021, Russia 1 Industrial Technology Research Institute, Hsinchu 310, Taiwan, R.O.C. on leave from A.F.Ioffe Physco Technical Institute ABSTRACT (In)GaAsN based heterostructures have been found to be promising candidates for the active region of 1.3 micron VCSELs. However, (In)GaAsN bulk layers and quantum wells usually demonstrate lower photoluminescence intensity than their nitrogen-free analogues. Defects associated with lower temperature growth and N-related defects due to plasma cell operation and possible nonuniform distribution of nitrogen enhance the non-radiative recombination in N-contained layers. We studied the photoluminescence intensity of GaAsN layers as a function of N content in MBE grown samples using rf-plasma source. Increasing the growth temperature to as high as 520 0C in combination with the increase in the growth rate allowed us to avoid any N-related defects up to 1.5% of nitrogen. Low-temperature-growth defects can be removed by post-growth annealing. We achieved the same radiative efficiency of GaAsN samples grown at 520 0C with that of reference layer of GaAs grown at 600 0C. Compositional fluctuations in GaAsN layers lead to characteristic S-shape of temperature dependence of photoluminescence peak position and this feature is the more pronounced the higher the amount of nitrogen in GaAsN. Annealing reduces compositional fluctuations in addition to the increase in the photoluminescence intensity. The results obtained are important for further improving the characteristics of InGaAsN lasers emitting at 1.3 micron. INTRODUCTION Group-III nitride semiconductors are an area of great current interest for the development of lasers and light emitting diodes emitting in the visible to blue and UV ranges. On the other hand, addition of a small amount of nitrogen to GaAs can drastically reduce the band gap towards the infrared region [1]. This is due to the strong bowing of the energy gap in the GaAsGaN system [2]. The large lattice mismatch between GaAs and GaN (about 21%) limits the composition range of GaAsN pseudomorphically grown on GaAs to only a few percent. The addition of In to GaAsN can lead to strain compensation, and a further decrease in the band gap of the quaternary solid solution can be obtained [3]. However, the growth of InGaAsN layers and quantum well structures of device quality appears to be a challenge even when the amount of nitrogen is less than 3 percent [4]. This is usually enough to achieve emission at 1.3 micron, which is the goal for applications in fiber optic communication systems. 1.3 micron edgeemitting lasers and VCSELs have been recently demonstrated by several research groups [5-8], however, the device characteristics are still basically inferior to those based on I
Data Loading...
