Professor Robert Taylor

Abstract:

The Kerr gate technique is used to time-resolve the gain in an In0.02Ga0.98N/In0.16Ga0.84N multiple quantum well sample. A new way of analyzing the data in such a variable stripe length method gain experiment is used to analyze the time-resolved spectra. The dynamics of the emission and gain are discussed. These measurements suggest that the photoexcited carriers must localize (possibly at indium-rich sites) before strong stimulated emission is seen. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract:

We have studied the growth of InGaN epitaxial layers on GaN by MOVPE (metal-organic vapour phase epitaxy), and have discovered that nanostructures may be formed if a flat epilayer is annealed in molecular nitrogen immediately after growth. The size and density of the nanostructures are shown to be dependent on the growth/anneal temperature. We demonstrated the quantum dot nature of our nanostructures by performing spatially resolved photoluminescence on samples that had been capped with a layer of GaN, grown at the same temperature as the InGaN epilayer. This revealed narrow, delta-function-like lines in the luminescence spectrum with full width at half maximum (FWHM) limited by the resolution of the spectrometer at 4.2 K. Measurement of the FWHM as a function of temperature revealed significant broadening above 20 K. (C) 2003 WILEY-VCH Vertag GmbH & Co. KGaA, Weinheim

Abstract:

The Kerr gate technique is used to time-resolve the gain in an In0.02Ga0.98N/In0.16Ga0.84N multiple quantum well sample. A new way of analyzing the data in such a variable stripe length method gain experiment is used to analyze both the time-integrated and time-resolved spectra. We confirm that the stripe length dependence of the gain in the multiple quantum wells under nanosecond excitation is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity. This is found to fit very well with our data, even beyond the saturation region. Furthermore, we have extended the investigation to examine the dynamics of the emission and gain. These measurements suggest that the photoexcited carriers must localize (possibly at indium-rich sites) before strong stimulated emission is seen. © 2002 Elsevier Science B.V. All rights reserved.

Abstract:

The Kerr gate technique is used to time-resolve the gain in an In0.02Ga0.98N/In0.16Ga0.84N multiple quantum well sample. A new way of analyzing the data in such a variable stripe length method gain experiment is used to analyze both the time-integrated and time-resolved spectra. We confirm that the stripe length dependence of the gain in the multiple quantum wells under nanosecond excitation is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity. This is found to fit very well with our data, even beyond the saturation region. Furthermore, we have extended the investigation to examine the dynamics of the emission and gain. These measurements suggest that the photoexcited carriers must localize (possibly at indium-rich sites) before strong stimulated emission is seen. (C) 2002 Elsevier Science B.V. All rights reserved.