TIME RESOLVED SPECTROSCOPY OF TERNARY SEMICONDUCTORS GALLIUM(X)-INDIUM(1-X) PHOSPHIDE AND GALLIUM-ARSENIDE(1-X)-PHOSPHIDE(X) UNDER PICOSECOND LASER PULSE EXCITATION

In the thesis, the ultrafast physics of carriers in two ternary semiconductors GA(,x)In(,1-x)P and GaAs(,1-x)P(,x) were studied under picosecond Laser Pulse Excitation.;The time resolved photoluminescence spectra in Ga(,.56)In(,.44)P was measured with 10 ps time resolution using the streak camera as a detection system. From the theoretical fitting of the photoluminescence spectra we have determined the time evolution of carrier density and carrier temperature. We found that the carrier energy loss rate to be slower than predicted from a simple model assuming a Maxwell Boltzmann distribution function. This is attributed to the screening of the hot carrier energy relaxation under high carrier densities. Integro-differential equations describing the time dependence of carrier temperature have been solved and the results are compared with the experimental data.;The time resolved photoluminescence kinetics in GaAs(,.62)P(,.38), were measured by streak camera to determine the radiative, non radiative recombination rates. The photoluminescence decay profile was found to be intensity dependent. When excitation power fluence increased above 6 x 10('8) W/cm('2), the decay profile of emission deviated from an exponential form. This is attributed to bimolecular and Auger processes. The biomolecular and Auger rates were determined to be B(,R) = 9 x 10('-10)cm('-3)/s and C(,NR) = 3 x 10('-29)cm('6)/s by fitting the time resolved photoluminescence decay profiles to the solution of rate equations which describes the dynamical behavior of the photogenerated carriers.;The dynamics of hot carriers In Ga(,.5)In(,.5)P, were studied by means of time resolved spectroscopy. The effect of high pump intensity on the temporal behavior of the emission at different wavelengths were investigated. At high excitation power fluence, the temporal profile at short wavelengths (high energy portion of the photoluminescence spectra) were exponential similar to the low excitation power fluence. However the temporal profiles at long wavelengths (low energy portion of the photoluminescence spectra close to band edge) exhibited an unusual and complex profile. The time resolved profiles at long wavelength acquired a district tail as excitation power increased even to the point of developing a second peak. A model is proposed to explain the temporal behavior of the emission at different wavelengths. The rate equations describing the time dependence of dynamical variables (n(,e), T(,c), (phi)((nu))) were solved numerically by computer to simulate the temporal behavior of the emission at different wavelengths under different excitation power fluence.