2D-1D crossover from quantum well to quantum wire behaviour in GaAs v-groove structures
PHYSICA E 13:2-4 (2002) 174-177
Abstract:
he distribution of electron current in GaAs AlGaAs v-groove quantum wire structures with groove widths varying from 1 to 25 mum has been studied using far- and near-field spectroscopy techniques. We find clear evidence of the formation of 'corner' quantum wires in wide grooves which coalesce to form single wires in grooves with widths narrower than similar to 5 mum. Spatially resolved photoluminescence measurements in the presence of an applied voltage provide information about the distribution of current in the device. (C) 2002 Elsevier Science B.V. All rights reserved.Hot phonons and non-thermal carrier states in GaN
PHYSICA B 314:1-4 (2002) 30-34
Abstract:
Non-thermal carrier states at early times are studied using femtosecond pump-probe spectroscopy in GaN. After the residual chirp on the continuum probe is removed, the normalized difference spectra (NDS) for different probe energies are synchronized, recovering the full time resolution of our laser pulse (120 fs). Our Monte-Carlo simulation agree well with the unchirped NDS spectrum, which shows the development of the carrier distribution at early times, where phonon satellites are seen. together with a strong non-thermal electron distribution in the region of the LO-phonon energy arising from the remarkably strong electron-LO phonon interaction. Employing a new technique which involves the integration of the normalized NDS multiplied by the corresponding energy, a measure of the mean energy of the carriers in non-thermal states is obtained. By comparing the time-dependent energy loss with the theoretical energy loss rate, we estimate the effective temperature of the phonon modes as well as the population of phonons. Our Monte-Carlo model agrees well with this data, and confirms the dominance of hot phonon effects at early times. (C) 2002 Elsevier Science B.V. All rights reserved.Optical measurements of carrier relaxation and transport in single GaAs v-groove quantum wire structures
PHYSICA B 314:1-4 (2002) 413-416
Abstract:
Single GaAs v-groove quantum wire structures, of varying width, have been studied using near-field and far-field photoluminescence (PL) and photoluminescence excitation (PLE) techniques. Strong non-thermal behaviour has been observed in complex quasi-1D/2D systems at temperatures below 40 K. Spatially resolved PL measurements in the presence of an applied voltage provide information about the distribution of current in the grooves. We find evidence of real-space transfer of carriers at higher voltages. (C) 2002 Elsevier Science B.V. All rights reserved.Saturation of gain in In0.02Ga0.98N/In0.16Ga0.84N MQW plasmas
PHYSICA B 314:1-4 (2002) 47-51
Abstract:
A new way of analysing the data in a variable stripe length method gain experiment is presented. The stripe length dependence of the gain is measured in In0.02Ga0.98N/In0.16Ga0.84N multiple quantum wells (MQWs). We confirm that this arises from 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. Comparison with the PL and PLE spectra suggests that the optical gain arises from weakly localised states in the quantum well in our low-indium-content sample. (C) 2002 Elsevier Science B.V. All rights reserved.Analysis of gain saturation in In0.02 Ga0.98 N/In0.16 Ga0.84 N multiple quantum wells
Applied Physics Letters 79:21 (2001) 3434-3436