Chapter 2 deals with the effect of increasing impurity concentrations on the photoluminescence spectrum. We present results for the Si:
At the heart of this research is the construction of a colliding-pulse mode-locked CPM ring-dye laser. This laser outputs ultrashort optical pulses at a high repetition rate.
With a CPM laser, ultrafast semiconductor phenomena may be optically probed. In addition, using this laser to drive photoconductive circuit elements PCEsultrafast electrical pulses can be generated and sampled, allowing novel high-speed devices to be electronically probed.
The technique itself was investigated both theoretically and experimentally; it was applied to a variety of GaAs samples of interest in the development of high-speed devices.
Chapter 2 discusses the construction and alignment of the CPM laser, and the autocorrelator used to measure the ultrashort pulses. PECS is a pulse-probe technique that measures the cross-correlation of photo-excited populations.
PECS is theoretically investigated using a rate equation model for a simple three-level system consisting of an electron and hole band and a single trap level. The model is examined in the limits of radiative band-to-band dominated recombination, and capture-dominated recombination.
In the former limit, no PECS signal is observed. However, in the latter limit, the PECS signal from the band-to-band PL measures the cross-correlation of the excited electron-hole population, and, thus, the electron and hole lifetimes. At 77 K, the PECS signal behaves as in the simple model, and an electron-hole lifetime in the range ps is measured.
This is much less than the expected radiative lifetime, and therefore the recombination in SI GaAs is capture-dominated.
At 5 K, the behavior is more complicated, because of an acceptor, which is un-ionized at 5 K. The acceptor-related PL also shows complicated behavior: A fast decay is associated with the band-to-acceptor transition, and the donor-acceptor PL saturates, producing a PECS signal that is negative and decays slowly.
It is found that the PL intensity contrast between a bright and dark area correlates with the ratio of the lifetimes measured using PECS in these areas. Thus, the PL intensity contrast is due to the difference in the carrier lifetimes in the different regions. The differences in the behavior of the lifetimes in the bright and dark regions with temperature suggest that the lifetime-governing defects in the two regions are different.
Moreover, the defects are deep, and from the shortness of the lifetimes, neither defect is EL2. These results agree with earlier research, which indicated that defects are gettered and generated at these dislocations. The effects of surface recombination on the PL intensity and lifetimes in In-alloyed GaAs are important to the investigations of this chapter.Photoluminescence and X-ray Diffraction Analyses of Cadmium Zinc Telluride Crystals by Ramin Jamnejad timberdesignmag.com, University of Tehran, A Thesis Submitted in Partial Fulfillment.
Synthesis, Characterization, Photoluminescence and Magnetic Properties of Zinc Oxide Nanoparticles. Ph. D.
Thesis: Ningthoujam Surajkumar Singh CHAPTER 3 Synthesis, Characterization and Photoluminescence Study. limitations in time resolved photoluminescence of gallium nitride using a streak camera thesis thomas r.
jost, captain, usaf afit/gap/enp/ Su-Young Cha.
thesis on photoluminescence K Chen. Z Yu. This thesis concerns the study of ultrafast phenomena in semiconductor physics. At the heart of this research is the construction of a colliding-pulse mode-locked (CPM) ring-dye laser. This laser outputs ultrashort optical pulses at a high repetition rate.
With a CPM laser, ultrafast semiconductor phenomena may be optically probed. In addition, using this laser to drive photoconductive circuit.
In this thesis, three examples of the application of the photoluminescence technique to indirect semiconductors at low temperatures are presented.
Chapter 2 deals with the effect of increasing impurity concentrations on the photoluminescence spectrum. We present results for the Si:(B,In) system. As the In concentration is increased, we observe quenching of B luminescence.