P. Díaz

PHOTOACOUSTIC DETERMINATION OF THE RECOMBINATION VELOCITY AT THE ALGAAS/GAAS HETEROSTRUCTURE INTERFACE

The surface recombination velocity at the AlGaAs/GaAs single heterostructure interface is determined using the photoacoustic technique. We analyze different heat generation mechanisms for this type of heterostructure with different Al composition and thickness of the AlGaAs layers. A theoretical model of the photoacoustic signal generation in the heat transmission detection configuration was developed. The values of the surface recombination velocity obtained by comparing the theoretical expressions with the experimental results are in good agreement with the literature reported ones. The results were also correlated with those of photoluminescence measurements in the same samples.

On the photoacoustic characterization of semiconductors : Influence of carrier recombination on the thermodiffusion, thermoelastic and electronic strain signal generation mechanisms

A quantitative study of the photoacoustic (PA) signal dependence on the modulation frequency in semiconductors was performed. The carrier recombination processes were taken into account to calculate the PA signal, considering the thermodiffusion (TD), thermoelastic (TE) and electronic strain (ES) signal generation mechanisms. Analytical expressions for these contributions and for the total pressure in the PA gas chamber are given for the heat transmission detection configuration. The theoretical results were compared with measurements in Si samples, showing a good agreement. An anomalous behavior of the PA signal dependence on the modulation frequency can only be explained, if the ES contribution is added to the other ones.

Influence of cavity length and emission wavelength on the characteristic temperature in AlGaAs lasers

The dependence of the characteristic temperature T0 on the cavity length and lasing wavelength is theoretical and experimentally analyzed. The devices are straight separate confinement heterostructure lasers with active layer thickness of 30 and 12 nm grown by low temperature liquid phase epitaxy. The recent observation that for very short lasers T0 is an increasing function of the cavity length is confirmed, and explained in terms of the threshold current cavity length dependence. The temperature dependence of the threshold current Ith gives T0 as high as 307 K for a quantum well laser with cavity length L=168 μm.The dependence of the characteristic temperature T0 on the cavity length and lasing wavelength is theoretical and experimentally analyzed. The devices are straight separate confinement heterostructure lasers with active layer thickness of 30 and 12 nm grown by low temperature liquid phase epitaxy. The recent observation that for very short lasers T0 is an increasing function of the cavity length is confirmed, and explained in terms of the threshold current cavity length dependence. The temperature dependence of the threshold current Ith gives T0 as high as 307 K for a quantum well laser with cavity length L=168 μm.

Cavity length dependence of the peak conversion efficiency in AlGaAs lasers

The dependence of the peak power conversion efficiency ηcpeak on the cavity length and lasing wavelength is theoretically and experimentally analyzed for straight separate confinement heterostructures AlGaAs lasers with an active layer thickness of 30 nm. A simple model that considers the dependence on cavity length of different diode parameters was used for theoretical estimations. The internal quantum efficiency is considered cavity‐length dependent. It was found that the optimum cavity length which maximizes the power conversion efficiency depends upon the laser emission wavelength.